Merge remote-tracking branch 'remote/main' into remove-json

Cargo.lock

@@ -358,6 +358,16 @@ version = "3.12.2"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "3c6ed94e98ecff0c12dd1b04c15ec0d7d9458ca8fe806cea6f12954efe74c63b"
 
+[[package]]
+name = "byte-unit"
+version = "4.0.19"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "da78b32057b8fdfc352504708feeba7216dcd65a2c9ab02978cbd288d1279b6c"
+dependencies = [
+ "serde",
+ "utf8-width",
+]
+
 [[package]]
 name = "bytemuck"
 version = "1.13.1"
@@ -3850,6 +3860,7 @@ name = "roc_reporting"
 version = "0.0.1"
 dependencies = [
  "bumpalo",
+ "byte-unit",
  "distance",
  "indoc",
  "insta",

crates/ast/src/lang/env.rs

@@ -121,16 +121,18 @@ impl<'a> Env<'a> {
 
                             Ok(symbol)
                         }
-                        None => Err(RuntimeError::LookupNotInScope(
+                        None => Err(RuntimeError::LookupNotInScope {
-                            Loc {
+                            loc_name: Loc {
                                 value: Ident::from(ident),
                                 region,
                             },
-                            self.ident_ids
+                            suggestion_options: self
+                                .ident_ids
                                 .ident_strs()
                                 .map(|(_, string)| string.into())
                                 .collect(),
-                        )),
+                            underscored_suggestion_region: None,
+                        }),
                     }
                 } else {
                     match self.dep_idents.get(&module_id) {

crates/ast/src/lang/scope.rs

@@ -203,13 +203,14 @@ impl Scope {
     pub fn lookup(&mut self, ident: &Ident, region: Region) -> Result<Symbol, RuntimeError> {
         match self.idents.get(ident) {
             Some((symbol, _)) => Ok(*symbol),
-            None => Err(RuntimeError::LookupNotInScope(
+            None => Err(RuntimeError::LookupNotInScope {
-                Loc {
+                loc_name: Loc {
                     region,
                     value: ident.clone().into(),
                 },
-                self.idents.keys().map(|v| v.as_ref().into()).collect(),
+                suggestion_options: self.idents.keys().map(|v| v.as_ref().into()).collect(),
-            )),
+                underscored_suggestion_region: None,
+            }),
         }
     }
 

crates/cli/tests/fixtures/multi-dep-str/platform/host.zig

@@ -48,10 +48,6 @@ export fn roc_dealloc(c_ptr: *anyopaque, alignment: u32) callconv(.C) void {
     free(@alignCast(16, @ptrCast([*]u8, c_ptr)));
 }
 
-export fn roc_memcpy(dst: [*]u8, src: [*]u8, size: usize) callconv(.C) void {
-    return memcpy(dst, src, size);
-}
-
 export fn roc_memset(dst: [*]u8, value: i32, size: usize) callconv(.C) void {
     return memset(dst, value, size);
 }

crates/cli/tests/fixtures/multi-dep-thunk/platform/host.zig

@@ -47,10 +47,6 @@ export fn roc_dealloc(c_ptr: *anyopaque, alignment: u32) callconv(.C) void {
     free(@alignCast(16, @ptrCast([*]u8, c_ptr)));
 }
 
-export fn roc_memcpy(dst: [*]u8, src: [*]u8, size: usize) callconv(.C) void {
-    return memcpy(dst, src, size);
-}
-
 export fn roc_memset(dst: [*]u8, value: i32, size: usize) callconv(.C) void {
     return memset(dst, value, size);
 }

crates/cli/tests/fixtures/packages/platform/host.zig

@@ -48,10 +48,6 @@ export fn roc_dealloc(c_ptr: *anyopaque, alignment: u32) callconv(.C) void {
     free(@alignCast(16, @ptrCast([*]u8, c_ptr)));
 }
 
-export fn roc_memcpy(dst: [*]u8, src: [*]u8, size: usize) callconv(.C) void {
-    return memcpy(dst, src, size);
-}
-
 export fn roc_memset(dst: [*]u8, value: i32, size: usize) callconv(.C) void {
     return memset(dst, value, size);
 }

crates/cli_testing_examples/algorithms/fibonacci-platform/host.zig

@@ -73,10 +73,6 @@ export fn roc_panic(c_ptr: *anyopaque, tag_id: u32) callconv(.C) void {
     std.process.exit(0);
 }
 
-export fn roc_memcpy(dst: [*]u8, src: [*]u8, size: usize) callconv(.C) void {
-    return memcpy(dst, src, size);
-}
-
 export fn roc_memset(dst: [*]u8, value: i32, size: usize) callconv(.C) void {
     return memset(dst, value, size);
 }

crates/cli_testing_examples/algorithms/quicksort-platform/host.zig

@@ -72,10 +72,6 @@ export fn roc_panic(c_ptr: *anyopaque, tag_id: u32) callconv(.C) void {
     std.process.exit(0);
 }
 
-export fn roc_memcpy(dst: [*]u8, src: [*]u8, size: usize) callconv(.C) void {
-    return memcpy(dst, src, size);
-}
-
 export fn roc_memset(dst: [*]u8, value: i32, size: usize) callconv(.C) void {
     return memset(dst, value, size);
 }

crates/cli_testing_examples/benchmarks/platform/host.zig

@@ -77,10 +77,6 @@ export fn roc_panic(c_ptr: *anyopaque, tag_id: u32) callconv(.C) void {
     std.process.exit(0);
 }
 
-export fn roc_memcpy(dst: [*]u8, src: [*]u8, size: usize) callconv(.C) void {
-    return memcpy(dst, src, size);
-}
-
 export fn roc_memset(dst: [*]u8, value: i32, size: usize) callconv(.C) void {
     return memset(dst, value, size);
 }

crates/cli_testing_examples/expects/zig-platform/host.zig

@@ -67,10 +67,6 @@ export fn roc_panic(c_ptr: *anyopaque, tag_id: u32) callconv(.C) void {
     std.process.exit(0);
 }
 
-export fn roc_memcpy(dst: [*]u8, src: [*]u8, size: usize) callconv(.C) void {
-    return memcpy(dst, src, size);
-}
-
 export fn roc_memset(dst: [*]u8, value: i32, size: usize) callconv(.C) void {
     return memset(dst, value, size);
 }

crates/compiler/build/src/program.rs

@@ -34,7 +34,9 @@ pub const DEFAULT_ROC_FILENAME: &str = "main.roc";
 
 #[derive(Debug, Clone, Copy, Default)]
 pub struct CodeGenTiming {
-    pub code_gen: Duration,
+    pub generate_final_ir: Duration,
+    pub code_gen_object: Duration,
+    pub total: Duration,
 }
 
 pub fn report_problems_monomorphized(loaded: &mut MonomorphizedModule) -> Problems {
@@ -144,7 +146,7 @@ fn gen_from_mono_module_llvm<'a>(
     use inkwell::module::Linkage;
     use inkwell::targets::{FileType, RelocMode};
 
-    let code_gen_start = Instant::now();
+    let all_code_gen_start = Instant::now();
 
     // Generate the binary
     let target_info = roc_target::TargetInfo::from(target);
@@ -238,6 +240,10 @@ fn gen_from_mono_module_llvm<'a>(
         &loaded.glue_layouts,
     );
 
+    // We are now finished building the LLVM IR.
+    let generate_final_ir = all_code_gen_start.elapsed();
+    let code_gen_object_start = Instant::now();
+
     env.dibuilder.finalize();
 
     // we don't use the debug info, and it causes weird errors.
@@ -439,11 +445,16 @@ fn gen_from_mono_module_llvm<'a>(
         }
     };
 
-    let code_gen = code_gen_start.elapsed();
+    let code_gen_object = code_gen_object_start.elapsed();
+    let total = all_code_gen_start.elapsed();
 
     (
         CodeObject::MemoryBuffer(memory_buffer),
-        CodeGenTiming { code_gen },
+        CodeGenTiming {
+            generate_final_ir,
+            code_gen_object,
+            total,
+        },
         ExpectMetadata {
             interns: env.interns,
             layout_interner: loaded.layout_interner,
@@ -503,7 +514,7 @@ fn gen_from_mono_module_dev_wasm32<'a>(
     preprocessed_host_path: &Path,
     wasm_dev_stack_bytes: Option<u32>,
 ) -> GenFromMono<'a> {
-    let code_gen_start = Instant::now();
+    let all_code_gen_start = Instant::now();
     let MonomorphizedModule {
         module_id,
         procedures,
@@ -550,11 +561,18 @@ fn gen_from_mono_module_dev_wasm32<'a>(
         procedures,
     );
 
-    let code_gen = code_gen_start.elapsed();
+    let generate_final_ir = all_code_gen_start.elapsed();
+    let code_gen_object_start = Instant::now();
+    let code_gen_object = code_gen_object_start.elapsed();
+    let total = all_code_gen_start.elapsed();
 
     (
         CodeObject::Vector(final_binary_bytes),
-        CodeGenTiming { code_gen },
+        CodeGenTiming {
+            generate_final_ir,
+            code_gen_object,
+            total,
+        },
         ExpectMetadata {
             interns,
             layout_interner,
@@ -569,7 +587,7 @@ fn gen_from_mono_module_dev_assembly<'a>(
     target: &target_lexicon::Triple,
     backend_mode: AssemblyBackendMode,
 ) -> GenFromMono<'a> {
-    let code_gen_start = Instant::now();
+    let all_code_gen_start = Instant::now();
 
     let lazy_literals = true;
 
@@ -593,15 +611,23 @@ fn gen_from_mono_module_dev_assembly<'a>(
     let module_object =
         roc_gen_dev::build_module(&env, &mut interns, &mut layout_interner, target, procedures);
 
-    let code_gen = code_gen_start.elapsed();
+    let generate_final_ir = all_code_gen_start.elapsed();
+    let code_gen_object_start = Instant::now();
 
     let module_out = module_object
         .write()
         .expect("failed to build output object");
 
+    let code_gen_object = code_gen_object_start.elapsed();
+    let total = all_code_gen_start.elapsed();
+
     (
         CodeObject::Vector(module_out),
-        CodeGenTiming { code_gen },
+        CodeGenTiming {
+            generate_final_ir,
+            code_gen_object,
+            total,
+        },
         ExpectMetadata {
             interns,
             layout_interner,
@@ -919,9 +945,12 @@ fn build_loaded_file<'a>(
 
     report_timing(
         buf,
-        "Generate Assembly from Mono IR",
+        "Generate final IR from Mono IR",
-        code_gen_timing.code_gen,
+        code_gen_timing.generate_final_ir,
     );
+    report_timing(buf, "Generate object", code_gen_timing.code_gen_object);
+    buf.push('\n');
+    report_timing(buf, "Total", code_gen_timing.total);
 
     let compilation_end = compilation_start.elapsed();
     let size = roc_app_bytes.len();

crates/compiler/builtins/bitcode/src/libc.zig

@@ -0,0 +1,80 @@
+const std = @import("std");
+const builtin = @import("builtin");
+const arch = builtin.cpu.arch;
+const musl = @import("libc/musl.zig");
+const folly = @import("libc/folly.zig");
+const cpuid = @import("libc/cpuid.zig");
+
+comptime {
+    // TODO: remove this workaround.
+    // Our wasm llvm pipeline always links in memcpy.
+    // As such, our impl will conflict.
+    if (arch != .wasm32) {
+        @export(memcpy, .{ .name = "memcpy", .linkage = .Strong });
+    }
+}
+
+const Memcpy = fn (noalias [*]u8, noalias [*]const u8, len: usize) callconv(.C) [*]u8;
+
+pub var memcpy_target: Memcpy = switch (arch) {
+    .x86_64 => dispatch_memcpy,
+    else => unreachable,
+};
+
+pub fn memcpy(noalias dest: [*]u8, noalias src: [*]const u8, len: usize) callconv(.C) [*]u8 {
+    switch (arch) {
+        // x86_64 has a special optimized memcpy that can use avx2.
+        .x86_64 => {
+            return memcpy_target(dest, src, len);
+        },
+        else => {
+            return musl.memcpy(dest, src, len);
+        },
+    }
+}
+
+const MemcpyDecision = enum {
+    uninitialized,
+    folly_prefetchw,
+    folly_prefetcht0,
+    musl,
+};
+
+var memcpy_decision: MemcpyDecision = .uninitialized;
+
+fn dispatch_memcpy(noalias dest: [*]u8, noalias src: [*]const u8, len: usize) callconv(.C) [*]u8 {
+    switch (arch) {
+        .x86_64 => {
+            // TODO: Switch this to overwrite the memcpy_target pointer once the surgical linker can support it.
+            // Then dispatch will just happen on the first call instead of every call.
+            // if (cpuid.supports_avx2()) {
+            //     if (cpuid.supports_prefetchw()) {
+            //         memcpy_target = folly.memcpy_prefetchw;
+            //     } else {
+            //         memcpy_target = folly.memcpy_prefetcht0;
+            //     }
+            // } else {
+            //     memcpy_target = musl.memcpy;
+            // }
+            // return memcpy_target(dest, src, len);
+            switch (memcpy_decision) {
+                .uninitialized => {
+                    if (cpuid.supports_avx2()) {
+                        if (cpuid.supports_prefetchw()) {
+                            memcpy_decision = .folly_prefetchw;
+                        } else {
+                            memcpy_decision = .folly_prefetcht0;
+                        }
+                    } else {
+                        memcpy_decision = .musl;
+                    }
+                    return dispatch_memcpy(dest, src, len);
+                },
+                .folly_prefetchw => return folly.memcpy_prefetchw(dest, src, len),
+                .folly_prefetcht0 => return folly.memcpy_prefetcht0(dest, src, len),
+                .musl => return musl.memcpy(dest, src, len),
+            }
+        },
+        else => unreachable,
+    }
+}

crates/compiler/builtins/bitcode/src/libc/assembly_util.zig

@@ -0,0 +1,7 @@
+const builtin = @import("builtin");
+const os = builtin.os;
+
+pub const function_prefix = switch (os.tag) {
+    .macos => "_",
+    else => "",
+};

crates/compiler/builtins/bitcode/src/libc/cpuid.S

@@ -0,0 +1,53 @@
+// Check if AVX2 is supported.
+// Returns 1 if AVX2 is supported, 0 otherwise.
+.global {[function_prefix]s}supports_avx2;
+{[function_prefix]s}supports_avx2:
+    // Save the EBX register.
+    push %rbx
+
+    // Call the CPUID instruction with the EAX register set to 7 and ECX set to 0.
+    // This will get the CPUID information for the current CPU.
+    mov $7, %eax
+    mov $0, %ecx
+    cpuid
+
+    // The AVX2 feature flag is located in the EBX register at bit 5.
+    bt $5, %ebx
+    jc .avx2_supported
+
+    // AVX2 is not supported.
+    pop %rbx
+    mov $0, %eax
+    ret
+
+    .avx2_supported:
+    pop %rbx
+    mov $1, %eax
+    ret
+
+ // Check if prefetchw is supported.
+ // Returns 1 if the prefetchw instruction is supported, 0 otherwise.
+.global {[function_prefix]s}supports_prefetchw;
+{[function_prefix]s}supports_prefetchw:
+    // Save the EBX register.
+    push %rbx
+
+    // Call the CPUID instruction with the EAX register set to 0x80000001 and ECX set to 0.
+    // This will get the CPUID information for the current CPU.
+    mov $0x80000001, %eax
+    mov $0, %ecx
+    cpuid
+
+    // The prefetchw feature flag is located in the ECX register at bit 8.
+    bt $8, %ecx
+    jc .prefetchw_supported
+
+    // AVX2 is not supported.
+    pop %rbx
+    mov $0, %eax
+    ret
+
+    .prefetchw_supported:
+    pop %rbx
+    mov $1, %eax
+    ret

crates/compiler/builtins/bitcode/src/libc/cpuid.zig

@@ -0,0 +1,18 @@
+const std = @import("std");
+const builtin = @import("builtin");
+const arch = builtin.cpu.arch;
+const function_prefix = @import("assembly_util.zig").function_prefix;
+
+// I couldn't manage to define this in a PIE friendly way with inline assembly.
+// Instead, I am defining it as global assembly functions.
+comptime {
+    switch (arch) {
+        .x86_64 => {
+            asm (std.fmt.comptimePrint(@embedFile("cpuid.S"), .{ .function_prefix = function_prefix }));
+        },
+        else => unreachable,
+    }
+}
+
+pub extern fn supports_avx2() bool;
+pub extern fn supports_prefetchw() bool;

crates/compiler/builtins/bitcode/src/libc/folly.zig

@@ -0,0 +1,2 @@
+pub const memcpy_prefetchw = @import("folly/memcpy.zig").__folly_memcpy_prefetchw;
+pub const memcpy_prefetcht0 = @import("folly/memcpy.zig").__folly_memcpy_prefetcht0;

crates/compiler/builtins/bitcode/src/libc/folly/memcpy-x86_64.S

@@ -0,0 +1,437 @@
+/*
+ * Copyright (c) Meta Platforms, Inc. and affiliates.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+/*
+ * __folly_memcpy: An optimized memcpy implementation that uses prefetch and
+ * AVX2 instructions.
+ *
+ * This implementation of memcpy acts as a memmove: while overlapping copies
+ * are undefined in memcpy, in some implementations they're the same function and
+ * legacy programs rely on this behavior.
+ *
+ * This implementation uses prefetch to avoid dtlb misses. This can
+ * substantially reduce dtlb store misses in cases where the destination
+ * location is absent from L1 cache and where the copy size is small enough
+ * that the hardware prefetcher doesn't have a large impact.
+ *
+ * The number of branches is limited by the use of overlapping loads & stores.
+ * This helps with copies where the source and destination cache lines are already
+ * present in L1 because there are fewer instructions to execute and fewer
+ * branches to potentially mispredict.
+ *   e.g. to copy the last 4 <= n <= 7 bytes: copy the first & last 4 bytes (overlapped):
+ *      movl        (%rsi), %r8d
+ *      movl        -4(%rsi,%rdx), %r9d
+ *      movl        %r8d, (%rdi)
+ *      movl        %r9d, -4(%rdi,%rdx)
+ *
+ *
+ * For sizes up to 256 all source data is first read into registers and then written:
+ * - n <=  16: overlapping movs
+ * - n <=  32: overlapping unaligned 16-byte SSE XMM load/stores
+ * - n <= 256: overlapping unaligned 32-byte AVX YMM load/stores
+ *
+ * Large copies (> 256 bytes) use unaligned loads + aligned stores.
+ * This is observed to always be faster than rep movsb, so the rep movsb
+ * instruction is not used.
+ * - The head & tail may be unaligned => they're always written using unaligned stores.
+ *
+ * If the copy size is humongous (> 32 KiB) and the source and destination are both
+ * aligned, this memcpy will use non-temporal operations (AVX2). This can have
+ * a substantial speedup for copies where data is absent from L1, but it
+ * is significantly slower if the source and destination data were already
+ * in L1. The use of non-temporal operations also has the effect that after
+ * the copy is complete, the data will be moved out of L1, even if the data was
+ * present before the copy started.
+ *
+ * For n > 256 and overlapping src & dst buffers (memmove):
+ * - use unaligned loads + aligned stores, but not non-temporal stores
+ * - for dst < src forward copy in 128 byte batches:
+ *   - unaligned load the first 32 bytes & last 4 x 32 bytes
+ *   - forward copy (unaligned load + aligned stores) 4 x 32 bytes at a time
+ *   - unaligned store the first 32 bytes & last 4 x 32 bytes
+ * - for dst > src backward copy in 128 byte batches:
+ *   - unaligned load the first 4 x 32 bytes & last 32 bytes
+ *   - backward copy (unaligned load + aligned stores) 4 x 32 bytes at a time
+ *   - unaligned store the first 4 x 32 bytes & last 32 bytes
+ *
+ * @author Logan Evans <lpe@fb.com>
+ */
+
+
+        // .type       {[function_prefix]s}__folly_memcpy_short_{[prefetch]s}, @function not supported by windows
+{[function_prefix]s}__folly_memcpy_short_{[prefetch]s}:
+        .cfi_startproc
+
+.L_GE1_LE7_{[prefetch]s}:
+        cmp         $1, %rdx
+        je          .L_EQ1_{[prefetch]s}
+
+        cmp         $4, %rdx
+        jae         .L_GE4_LE7_{[prefetch]s}
+
+.L_GE2_LE3_{[prefetch]s}:
+        movw        (%rsi), %r8w
+        movw        -2(%rsi,%rdx), %r9w
+        movw        %r8w, (%rdi)
+        movw        %r9w, -2(%rdi,%rdx)
+        ret
+
+        .balign      2
+.L_EQ1_{[prefetch]s}:
+        movb        (%rsi), %r8b
+        movb        %r8b, (%rdi)
+        ret
+
+        // Aligning the target of a jump to an even address has a measurable
+        // speedup in microbenchmarks.
+        .balign      2
+.L_GE4_LE7_{[prefetch]s}:
+        movl        (%rsi), %r8d
+        movl        -4(%rsi,%rdx), %r9d
+        movl        %r8d, (%rdi)
+        movl        %r9d, -4(%rdi,%rdx)
+        ret
+
+        .cfi_endproc
+        // .size       {[function_prefix]s}__folly_memcpy_short_{[prefetch]s}, .-{[function_prefix]s}__folly_memcpy_short_{[prefetch]s} not supported by windows
+
+// memcpy is an alternative entrypoint into the function named __folly_memcpy.
+// The compiler is able to call memcpy since the name is global while
+// stacktraces will show __folly_memcpy since that is the name of the function.
+// This is intended to aid in debugging by making it obvious which version of
+// memcpy is being used.
+        .balign      64
+        .globl      {[function_prefix]s}__folly_memcpy_{[prefetch]s}
+        // .type       {[function_prefix]s}__folly_memcpy_{[prefetch]s}, @function not supported by windows
+
+{[function_prefix]s}__folly_memcpy_{[prefetch]s}:
+        .cfi_startproc
+
+        mov         %rdi, %rax    // return: $rdi
+
+        test        %rdx, %rdx
+        je          .L_EQ0_{[prefetch]s}
+
+        {[prefetch]s}    (%rdi)
+        {[prefetch]s}    -1(%rdi,%rdx)
+
+        cmp         $8, %rdx
+        jb          .L_GE1_LE7_{[prefetch]s}
+
+.L_GE8_{[prefetch]s}:
+        cmp         $32, %rdx
+        ja          .L_GE33_{[prefetch]s}
+
+.L_GE8_LE32_{[prefetch]s}:
+        cmp         $16, %rdx
+        ja          .L_GE17_LE32_{[prefetch]s}
+
+.L_GE8_LE16_{[prefetch]s}:
+        mov         (%rsi), %r8
+        mov         -8(%rsi,%rdx), %r9
+        mov         %r8, (%rdi)
+        mov         %r9, -8(%rdi,%rdx)
+.L_EQ0_{[prefetch]s}:
+        ret
+
+        .balign      2
+.L_GE17_LE32_{[prefetch]s}:
+        movdqu      (%rsi), %xmm0
+        movdqu      -16(%rsi,%rdx), %xmm1
+        movdqu      %xmm0, (%rdi)
+        movdqu      %xmm1, -16(%rdi,%rdx)
+        ret
+
+        .balign      2
+.L_GE193_LE256_{[prefetch]s}:
+        vmovdqu     %ymm3, 96(%rdi)
+        vmovdqu     %ymm4, -128(%rdi,%rdx)
+
+.L_GE129_LE192_{[prefetch]s}:
+        vmovdqu     %ymm2, 64(%rdi)
+        vmovdqu     %ymm5, -96(%rdi,%rdx)
+
+.L_GE65_LE128_{[prefetch]s}:
+        vmovdqu     %ymm1, 32(%rdi)
+        vmovdqu     %ymm6, -64(%rdi,%rdx)
+
+.L_GE33_LE64_{[prefetch]s}:
+        vmovdqu     %ymm0, (%rdi)
+        vmovdqu     %ymm7, -32(%rdi,%rdx)
+
+        vzeroupper
+        ret
+
+        .balign      2
+.L_GE33_{[prefetch]s}:
+        vmovdqu     (%rsi), %ymm0
+        vmovdqu     -32(%rsi,%rdx), %ymm7
+
+        cmp         $64, %rdx
+        jbe         .L_GE33_LE64_{[prefetch]s}
+
+        {[prefetch]s}    64(%rdi)
+
+        vmovdqu     32(%rsi), %ymm1
+        vmovdqu     -64(%rsi,%rdx), %ymm6
+
+        cmp         $128, %rdx
+        jbe         .L_GE65_LE128_{[prefetch]s}
+
+        {[prefetch]s}    128(%rdi)
+
+        vmovdqu     64(%rsi), %ymm2
+        vmovdqu     -96(%rsi,%rdx), %ymm5
+
+        cmp         $192, %rdx
+        jbe         .L_GE129_LE192_{[prefetch]s}
+
+        {[prefetch]s}    192(%rdi)
+
+        vmovdqu     96(%rsi), %ymm3
+        vmovdqu     -128(%rsi,%rdx), %ymm4
+
+        cmp         $256, %rdx
+        jbe         .L_GE193_LE256_{[prefetch]s}
+
+.L_GE257_{[prefetch]s}:
+        {[prefetch]s}    256(%rdi)
+
+        // Check if there is an overlap. If there is an overlap then the caller
+        // has a bug since this is undefined behavior. However, for legacy
+        // reasons this behavior is expected by some callers.
+        //
+        // All copies through 256 bytes will operate as a memmove since for
+        // those sizes all reads are performed before any writes.
+        //
+        // This check uses the idea that there is an overlap if
+        // (%rdi < (%rsi + %rdx)) && (%rsi < (%rdi + %rdx)),
+        // or equivalently, there is no overlap if
+        // ((%rsi + %rdx) <= %rdi) || ((%rdi + %rdx) <= %rsi).
+        //
+        // %r9 will be used after .L_ALIGNED_DST_LOOP to calculate how many
+        // bytes remain to be copied.
+
+        // (%rsi + %rdx <= %rdi) => no overlap
+        lea         (%rsi,%rdx), %r9
+        cmp         %rdi, %r9
+        jbe         .L_NO_OVERLAP_{[prefetch]s}
+
+        // (%rdi + %rdx <= %rsi) => no overlap
+        lea         (%rdi,%rdx), %r8
+        cmp         %rsi, %r8
+        // If no info is available in branch predictor's cache, Intel CPUs assume
+        // forward jumps are not taken. Use a forward jump as overlapping buffers
+        // are unlikely.
+        ja          .L_OVERLAP_{[prefetch]s}
+
+        .balign      2
+.L_NO_OVERLAP_{[prefetch]s}:
+        vmovdqu     %ymm0, (%rdi)
+        vmovdqu     %ymm1, 32(%rdi)
+        vmovdqu     %ymm2, 64(%rdi)
+        vmovdqu     %ymm3, 96(%rdi)
+
+        // Align %rdi to a 32 byte boundary.
+        // %rcx = 128 - 31 & %rdi
+        mov         $128, %rcx
+        and         $31, %rdi
+        sub         %rdi, %rcx
+
+        lea         (%rsi,%rcx), %rsi
+        lea         (%rax,%rcx), %rdi
+        sub         %rcx, %rdx
+
+        // %r8 is the end condition for the loop.
+        lea         -128(%rsi,%rdx), %r8
+
+		// This threshold is half of L1 cache on a Skylake machine, which means that
+		// potentially all of L1 will be populated by this copy once it is executed
+		// (dst and src are cached for temporal copies).
+		// NON_TEMPORAL_STORE_THRESHOLD = $32768
+        // cmp         NON_TEMPORAL_STORE_THRESHOLD, %rdx
+        cmp         $32768, %rdx
+        jae         .L_NON_TEMPORAL_LOOP_{[prefetch]s}
+
+        .balign      2
+.L_ALIGNED_DST_LOOP_{[prefetch]s}:
+        {[prefetch]s}    128(%rdi)
+        {[prefetch]s}    192(%rdi)
+
+        vmovdqu     (%rsi), %ymm0
+        vmovdqu     32(%rsi), %ymm1
+        vmovdqu     64(%rsi), %ymm2
+        vmovdqu     96(%rsi), %ymm3
+        add         $128, %rsi
+
+        vmovdqa     %ymm0, (%rdi)
+        vmovdqa     %ymm1, 32(%rdi)
+        vmovdqa     %ymm2, 64(%rdi)
+        vmovdqa     %ymm3, 96(%rdi)
+        add         $128, %rdi
+
+        cmp         %r8, %rsi
+        jb          .L_ALIGNED_DST_LOOP_{[prefetch]s}
+
+.L_ALIGNED_DST_LOOP_END_{[prefetch]s}:
+        sub         %rsi, %r9
+        mov         %r9, %rdx
+
+        vmovdqu     %ymm4, -128(%rdi,%rdx)
+        vmovdqu     %ymm5, -96(%rdi,%rdx)
+        vmovdqu     %ymm6, -64(%rdi,%rdx)
+        vmovdqu     %ymm7, -32(%rdi,%rdx)
+
+        vzeroupper
+        ret
+
+        .balign      2
+.L_NON_TEMPORAL_LOOP_{[prefetch]s}:
+        testb       $31, %sil
+        jne         .L_ALIGNED_DST_LOOP_{[prefetch]s}
+        // This is prefetching the source data unlike ALIGNED_DST_LOOP which
+        // prefetches the destination data. This choice is again informed by
+        // benchmarks. With a non-temporal store the entirety of the cache line
+        // is being written so the previous data can be discarded without being
+        // fetched.
+        prefetchnta 128(%rsi)
+        prefetchnta 196(%rsi)
+
+        vmovntdqa   (%rsi), %ymm0
+        vmovntdqa   32(%rsi), %ymm1
+        vmovntdqa   64(%rsi), %ymm2
+        vmovntdqa   96(%rsi), %ymm3
+        add         $128, %rsi
+
+        vmovntdq    %ymm0, (%rdi)
+        vmovntdq    %ymm1, 32(%rdi)
+        vmovntdq    %ymm2, 64(%rdi)
+        vmovntdq    %ymm3, 96(%rdi)
+        add         $128, %rdi
+
+        cmp         %r8, %rsi
+        jb          .L_NON_TEMPORAL_LOOP_{[prefetch]s}
+
+        sfence
+        jmp         .L_ALIGNED_DST_LOOP_END_{[prefetch]s}
+
+
+.L_OVERLAP_{[prefetch]s}:
+        .balign      2
+        cmp         %rdi, %rsi
+        jb          .L_OVERLAP_BWD_{[prefetch]s}  // %rsi  < %rdi => backward-copy
+        je          .L_RET_{[prefetch]s}          // %rsi == %rdi => return, nothing to copy
+
+        // Source & destination buffers overlap. Forward copy.
+
+        vmovdqu     (%rsi), %ymm8
+
+        // Align %rdi to a 32 byte boundary.
+        // %rcx = 32 - 31 & %rdi
+        mov         $32, %rcx
+        and         $31, %rdi
+        sub         %rdi, %rcx
+
+        lea         (%rsi,%rcx), %rsi
+        lea         (%rax,%rcx), %rdi
+        sub         %rcx, %rdx
+
+        // %r8 is the end condition for the loop.
+        lea         -128(%rsi,%rdx), %r8
+
+
+.L_OVERLAP_FWD_ALIGNED_DST_LOOP_{[prefetch]s}:
+        {[prefetch]s}    128(%rdi)
+        {[prefetch]s}    192(%rdi)
+
+        vmovdqu       (%rsi), %ymm0
+        vmovdqu     32(%rsi), %ymm1
+        vmovdqu     64(%rsi), %ymm2
+        vmovdqu     96(%rsi), %ymm3
+        add         $128, %rsi
+
+        vmovdqa     %ymm0,   (%rdi)
+        vmovdqa     %ymm1, 32(%rdi)
+        vmovdqa     %ymm2, 64(%rdi)
+        vmovdqa     %ymm3, 96(%rdi)
+        add         $128, %rdi
+
+        cmp         %r8, %rsi
+        jb          .L_OVERLAP_FWD_ALIGNED_DST_LOOP_{[prefetch]s}
+
+        sub         %rsi, %r9
+        mov         %r9, %rdx
+
+        vmovdqu     %ymm4, -128(%rdi,%rdx)
+        vmovdqu     %ymm5,  -96(%rdi,%rdx)
+        vmovdqu     %ymm6,  -64(%rdi,%rdx)
+        vmovdqu     %ymm7,  -32(%rdi,%rdx)
+        vmovdqu     %ymm8, (%rax)  // %rax == the original (unaligned) %rdi
+
+        vzeroupper
+
+.L_RET_{[prefetch]s}:
+        ret
+
+.L_OVERLAP_BWD_{[prefetch]s}:
+        // Save last 32 bytes.
+        vmovdqu     -32(%rsi, %rdx), %ymm8
+        lea         -32(%rdi, %rdx), %r9
+
+
+        // %r8 is the end condition for the loop.
+        lea         128(%rsi), %r8
+
+        // Align %rdi+%rdx (destination end) to a 32 byte boundary.
+        // %rcx = (%rdi + %rdx - 32) & 31
+        mov         %r9, %rcx
+        and         $31, %rcx
+        // Set %rsi & %rdi to the end of the 32 byte aligned range.
+        sub         %rcx, %rdx
+        add         %rdx, %rsi
+        add         %rdx, %rdi
+
+
+.L_OVERLAP_BWD_ALIGNED_DST_LOOP_{[prefetch]s}:
+        {[prefetch]s}    -128(%rdi)
+        {[prefetch]s}    -192(%rdi)
+
+        vmovdqu      -32(%rsi), %ymm4
+        vmovdqu      -64(%rsi), %ymm5
+        vmovdqu      -96(%rsi), %ymm6
+        vmovdqu     -128(%rsi), %ymm7
+        sub         $128, %rsi
+
+        vmovdqa     %ymm4,  -32(%rdi)
+        vmovdqa     %ymm5,  -64(%rdi)
+        vmovdqa     %ymm6,  -96(%rdi)
+        vmovdqa     %ymm7, -128(%rdi)
+        sub         $128, %rdi
+
+        cmp         %r8, %rsi
+        ja          .L_OVERLAP_BWD_ALIGNED_DST_LOOP_{[prefetch]s}
+
+        vmovdqu     %ymm0,   (%rax)  // %rax == the original unaligned %rdi
+        vmovdqu     %ymm1, 32(%rax)
+        vmovdqu     %ymm2, 64(%rax)
+        vmovdqu     %ymm3, 96(%rax)
+        vmovdqu     %ymm8, (%r9)
+
+        vzeroupper
+	ret
+
+        .cfi_endproc
+        // .size       {[function_prefix]s}__folly_memcpy_{[prefetch]s}, .-{[function_prefix]s}__folly_memcpy_{[prefetch]s} not supported by windows

crates/compiler/builtins/bitcode/src/libc/folly/memcpy.zig

@@ -0,0 +1,18 @@
+const std = @import("std");
+const builtin = @import("builtin");
+const arch = builtin.cpu.arch;
+const function_prefix = @import("../assembly_util.zig").function_prefix;
+
+comptime {
+    switch (arch) {
+        .x86_64 => {
+            inline for ([_][]const u8{ "prefetchw", "prefetcht0" }) |prefetch| {
+                asm (std.fmt.comptimePrint(@embedFile("memcpy-x86_64.S"), .{ .prefetch = prefetch, .function_prefix = function_prefix }));
+            }
+        },
+        else => unreachable,
+    }
+}
+
+pub extern fn __folly_memcpy_prefetchw(noalias dest: [*]u8, noalias src: [*]const u8, len: usize) callconv(.C) [*]u8;
+pub extern fn __folly_memcpy_prefetcht0(noalias dest: [*]u8, noalias src: [*]const u8, len: usize) callconv(.C) [*]u8;

crates/compiler/builtins/bitcode/src/libc/musl.zig

@@ -0,0 +1 @@
+pub const memcpy = @import("musl/memcpy.zig").memcpy;

crates/compiler/builtins/bitcode/src/libc/musl/COPYRIGHT

@@ -0,0 +1,193 @@
+musl as a whole is licensed under the following standard MIT license:
+
+----------------------------------------------------------------------
+Copyright © 2005-2020 Rich Felker, et al.
+
+Permission is hereby granted, free of charge, to any person obtaining
+a copy of this software and associated documentation files (the
+"Software"), to deal in the Software without restriction, including
+without limitation the rights to use, copy, modify, merge, publish,
+distribute, sublicense, and/or sell copies of the Software, and to
+permit persons to whom the Software is furnished to do so, subject to
+the following conditions:
+
+The above copyright notice and this permission notice shall be
+included in all copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
+EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
+MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.
+IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY
+CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT,
+TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE
+SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+----------------------------------------------------------------------
+
+Authors/contributors include:
+
+A. Wilcox
+Ada Worcester
+Alex Dowad
+Alex Suykov
+Alexander Monakov
+Andre McCurdy
+Andrew Kelley
+Anthony G. Basile
+Aric Belsito
+Arvid Picciani
+Bartosz Brachaczek
+Benjamin Peterson
+Bobby Bingham
+Boris Brezillon
+Brent Cook
+Chris Spiegel
+Clément Vasseur
+Daniel Micay
+Daniel Sabogal
+Daurnimator
+David Carlier
+David Edelsohn
+Denys Vlasenko
+Dmitry Ivanov
+Dmitry V. Levin
+Drew DeVault
+Emil Renner Berthing
+Fangrui Song
+Felix Fietkau
+Felix Janda
+Gianluca Anzolin
+Hauke Mehrtens
+He X
+Hiltjo Posthuma
+Isaac Dunham
+Jaydeep Patil
+Jens Gustedt
+Jeremy Huntwork
+Jo-Philipp Wich
+Joakim Sindholt
+John Spencer
+Julien Ramseier
+Justin Cormack
+Kaarle Ritvanen
+Khem Raj
+Kylie McClain
+Leah Neukirchen
+Luca Barbato
+Luka Perkov
+M Farkas-Dyck (Strake)
+Mahesh Bodapati
+Markus Wichmann
+Masanori Ogino
+Michael Clark
+Michael Forney
+Mikhail Kremnyov
+Natanael Copa
+Nicholas J. Kain
+orc
+Pascal Cuoq
+Patrick Oppenlander
+Petr Hosek
+Petr Skocik
+Pierre Carrier
+Reini Urban
+Rich Felker
+Richard Pennington
+Ryan Fairfax
+Samuel Holland
+Segev Finer
+Shiz
+sin
+Solar Designer
+Stefan Kristiansson
+Stefan O'Rear
+Szabolcs Nagy
+Timo Teräs
+Trutz Behn
+Valentin Ochs
+Will Dietz
+William Haddon
+William Pitcock
+
+Portions of this software are derived from third-party works licensed
+under terms compatible with the above MIT license:
+
+The TRE regular expression implementation (src/regex/reg* and
+src/regex/tre*) is Copyright © 2001-2008 Ville Laurikari and licensed
+under a 2-clause BSD license (license text in the source files). The
+included version has been heavily modified by Rich Felker in 2012, in
+the interests of size, simplicity, and namespace cleanliness.
+
+Much of the math library code (src/math/* and src/complex/*) is
+Copyright © 1993,2004 Sun Microsystems or
+Copyright © 2003-2011 David Schultz or
+Copyright © 2003-2009 Steven G. Kargl or
+Copyright © 2003-2009 Bruce D. Evans or
+Copyright © 2008 Stephen L. Moshier or
+Copyright © 2017-2018 Arm Limited
+and labelled as such in comments in the individual source files. All
+have been licensed under extremely permissive terms.
+
+The ARM memcpy code (src/string/arm/memcpy.S) is Copyright © 2008
+The Android Open Source Project and is licensed under a two-clause BSD
+license. It was taken from Bionic libc, used on Android.
+
+The AArch64 memcpy and memset code (src/string/aarch64/*) are
+Copyright © 1999-2019, Arm Limited.
+
+The implementation of DES for crypt (src/crypt/crypt_des.c) is
+Copyright © 1994 David Burren. It is licensed under a BSD license.
+
+The implementation of blowfish crypt (src/crypt/crypt_blowfish.c) was
+originally written by Solar Designer and placed into the public
+domain. The code also comes with a fallback permissive license for use
+in jurisdictions that may not recognize the public domain.
+
+The smoothsort implementation (src/stdlib/qsort.c) is Copyright © 2011
+Valentin Ochs and is licensed under an MIT-style license.
+
+The x86_64 port was written by Nicholas J. Kain and is licensed under
+the standard MIT terms.
+
+The mips and microblaze ports were originally written by Richard
+Pennington for use in the ellcc project. The original code was adapted
+by Rich Felker for build system and code conventions during upstream
+integration. It is licensed under the standard MIT terms.
+
+The mips64 port was contributed by Imagination Technologies and is
+licensed under the standard MIT terms.
+
+The powerpc port was also originally written by Richard Pennington,
+and later supplemented and integrated by John Spencer. It is licensed
+under the standard MIT terms.
+
+All other files which have no copyright comments are original works
+produced specifically for use as part of this library, written either
+by Rich Felker, the main author of the library, or by one or more
+contibutors listed above. Details on authorship of individual files
+can be found in the git version control history of the project. The
+omission of copyright and license comments in each file is in the
+interest of source tree size.
+
+In addition, permission is hereby granted for all public header files
+(include/* and arch/*/bits/*) and crt files intended to be linked into
+applications (crt/*, ldso/dlstart.c, and arch/*/crt_arch.h) to omit
+the copyright notice and permission notice otherwise required by the
+license, and to use these files without any requirement of
+attribution. These files include substantial contributions from:
+
+Bobby Bingham
+John Spencer
+Nicholas J. Kain
+Rich Felker
+Richard Pennington
+Stefan Kristiansson
+Szabolcs Nagy
+
+all of whom have explicitly granted such permission.
+
+This file previously contained text expressing a belief that most of
+the files covered by the above exception were sufficiently trivial not
+to be subject to copyright, resulting in confusion over whether it
+negated the permissions granted in the license. In the spirit of
+permissive licensing, and of not having licensing issues being an
+obstacle to adoption, that text has been removed.

crates/compiler/builtins/bitcode/src/libc/musl/README.md

@@ -0,0 +1,2 @@
+This set of files all come from [musl libc](https://musl.libc.org/).
+Roc just directly uses a few of them instead of depending on musl libc fully.

crates/compiler/builtins/bitcode/src/libc/musl/memcpy-i386.S

@@ -0,0 +1,30 @@
+.global {[function_prefix]s}musl_memcpy
+// Windows does not support the type directive.
+// .type {[function_prefix]s}musl_memcpy,@function
+{[function_prefix]s}musl_memcpy:
+	push %esi
+	push %edi
+	mov 12(%esp),%edi
+	mov 16(%esp),%esi
+	mov 20(%esp),%ecx
+	mov %edi,%eax
+	cmp $4,%ecx
+	jc 1f
+	test $3,%edi
+	jz 1f
+2:	movsb
+	dec %ecx
+	test $3,%edi
+	jnz 2b
+1:	mov %ecx,%edx
+	shr $2,%ecx
+	rep
+	movsl
+	and $3,%edx
+	jz 1f
+2:	movsb
+	dec %edx
+	jnz 2b
+1:	pop %edi
+	pop %esi
+	ret

crates/compiler/builtins/bitcode/src/libc/musl/memcpy-x86_64.S

@@ -0,0 +1,23 @@
+.global {[function_prefix]s}musl_memcpy
+// Windows does not support the type directive.
+// .type {[function_prefix]s}musl_memcpy,@function
+{[function_prefix]s}musl_memcpy:
+	mov %rdi,%rax
+	cmp $8,%rdx
+	jc 1f
+	test $7,%edi
+	jz 1f
+2:	movsb
+	dec %rdx
+	test $7,%edi
+	jnz 2b
+1:	mov %rdx,%rcx
+	shr $3,%rcx
+	rep
+	movsq
+	and $7,%edx
+	jz 1f
+2:	movsb
+	dec %edx
+	jnz 2b
+1:	ret

crates/compiler/builtins/bitcode/src/libc/musl/memcpy.zig

@@ -0,0 +1,201 @@
+const std = @import("std");
+const builtin = @import("builtin");
+const arch = builtin.cpu.arch;
+const function_prefix = @import("../assembly_util.zig").function_prefix;
+
+comptime {
+    switch (arch) {
+        .x86_64 => {
+            asm (std.fmt.comptimePrint(@embedFile("memcpy-x86_64.S"), .{ .function_prefix = function_prefix }));
+        },
+        .i386 => {
+            asm (std.fmt.comptimePrint(@embedFile("memcpy-i386.S"), .{ .function_prefix = function_prefix }));
+        },
+        // TODO: add assembly implementations for other platforms.
+        else => {},
+    }
+}
+
+pub const memcpy =
+    switch (arch) {
+    .x86_64, .i386 => musl_memcpy,
+    else => fallback_memcpy,
+};
+
+pub extern fn musl_memcpy(noalias dest: [*]u8, noalias src: [*]const u8, len: usize) callconv(.C) [*]u8;
+
+// Note: this is written to only support little endian targets.
+// To support big endian, `<<` and `>>` wold need to be swapped.
+pub fn fallback_memcpy(noalias dest: [*]u8, noalias src: [*]const u8, len: usize) callconv(.C) [*]u8 {
+    var d = dest;
+    var s = src;
+    var n = len;
+    while (@ptrToInt(s) % 4 != 0 and n != 0) : (n -= 1) {
+        d[0] = s[0];
+        d += 1;
+        s += 1;
+    }
+
+    if (@ptrToInt(d) % 4 == 0) {
+        var d4 = @alignCast(4, d);
+        var s4 = @alignCast(4, s);
+        while (n >= 16) : (n -= 16) {
+            var d_u32 = @ptrCast([*]u32, d4);
+            var s_u32 = @ptrCast([*]const u32, s4);
+            d_u32[0] = s_u32[0];
+            d_u32[1] = s_u32[1];
+            d_u32[2] = s_u32[2];
+            d_u32[3] = s_u32[3];
+
+            d4 += 16;
+            s4 += 16;
+        }
+        if (n & 8 != 0) {
+            var d_u32 = @ptrCast([*]u32, d4);
+            var s_u32 = @ptrCast([*]const u32, s4);
+            d_u32[0] = s_u32[0];
+            d_u32[1] = s_u32[1];
+
+            d4 += 8;
+            s4 += 8;
+        }
+        if (n & 4 != 0) {
+            var d_u32 = @ptrCast([*]u32, d4);
+            var s_u32 = @ptrCast([*]const u32, s4);
+            d_u32[0] = s_u32[0];
+
+            d4 += 4;
+            s4 += 4;
+        }
+        d = d4;
+        s = s4;
+        if (n & 2 != 0) {
+            d[0] = s[0];
+            d += 1;
+            s += 1;
+            d[0] = s[0];
+            d += 1;
+            s += 1;
+        }
+        if (n & 1 != 0) {
+            d[0] = s[0];
+        }
+        return dest;
+    }
+    if (n >= 32) {
+        switch (@ptrToInt(d) % 4) {
+            1 => {
+                var w = @ptrCast([*]const u32, @alignCast(4, s))[0];
+                d[0] = s[0];
+                d += 1;
+                s += 1;
+                d[0] = s[0];
+                d += 1;
+                s += 1;
+                d[0] = s[0];
+                d += 1;
+                s += 1;
+                n -= 3;
+                while (n >= 17) : (n -= 16) {
+                    var d_u32 = @ptrCast([*]u32, @alignCast(4, d));
+                    var s_u32 = @ptrCast([*]const u32, @alignCast(4, s + 1));
+                    var x = s_u32[0];
+                    d_u32[0] = (w >> 24) | (x << 8);
+                    w = s_u32[1];
+                    d_u32[1] = (x >> 24) | (w << 8);
+                    x = s_u32[2];
+                    d_u32[2] = (w >> 24) | (x << 8);
+                    w = s_u32[3];
+                    d_u32[3] = (x >> 24) | (w << 8);
+
+                    d += 16;
+                    s += 16;
+                }
+            },
+            2 => {
+                var w = @ptrCast([*]const u32, @alignCast(4, s))[0];
+                d[0] = s[0];
+                d += 1;
+                s += 1;
+                d[0] = s[0];
+                d += 1;
+                s += 1;
+                n -= 2;
+                while (n >= 18) : (n -= 16) {
+                    var d_u32 = @ptrCast([*]u32, @alignCast(4, d));
+                    var s_u32 = @ptrCast([*]const u32, @alignCast(4, s + 2));
+                    var x = s_u32[0];
+                    d_u32[0] = (w >> 16) | (x << 16);
+                    w = s_u32[1];
+                    d_u32[1] = (x >> 16) | (w << 16);
+                    x = s_u32[2];
+                    d_u32[2] = (w >> 16) | (x << 16);
+                    w = s_u32[3];
+                    d_u32[3] = (x >> 16) | (w << 16);
+
+                    d += 16;
+                    s += 16;
+                }
+            },
+            3 => {
+                var w = @ptrCast([*]const u32, @alignCast(4, s))[0];
+                d[0] = s[0];
+                d += 1;
+                s += 1;
+                n -= 1;
+                while (n >= 19) : (n -= 16) {
+                    var d_u32 = @ptrCast([*]u32, @alignCast(4, d));
+                    var s_u32 = @ptrCast([*]const u32, @alignCast(4, s + 3));
+                    var x = s_u32[0];
+                    d_u32[0] = (w >> 8) | (x << 24);
+                    w = s_u32[1];
+                    d_u32[1] = (x >> 8) | (w << 24);
+                    x = s_u32[2];
+                    d_u32[2] = (w >> 8) | (x << 24);
+                    w = s_u32[3];
+                    d_u32[3] = (x >> 8) | (w << 24);
+
+                    d += 16;
+                    s += 16;
+                }
+            },
+            else => unreachable,
+        }
+    }
+    if (n & 16 != 0) {
+        comptime var i = 0;
+        inline while (i < 16) : (i += 1) {
+            d[0] = s[0];
+            d += 1;
+            s += 1;
+        }
+    }
+    if (n & 8 != 0) {
+        comptime var i = 0;
+        inline while (i < 8) : (i += 1) {
+            d[0] = s[0];
+            d += 1;
+            s += 1;
+        }
+    }
+    if (n & 4 != 0) {
+        comptime var i = 0;
+        inline while (i < 4) : (i += 1) {
+            d[0] = s[0];
+            d += 1;
+            s += 1;
+        }
+    }
+    if (n & 2 != 0) {
+        d[0] = s[0];
+        d += 1;
+        s += 1;
+        d[0] = s[0];
+        d += 1;
+        s += 1;
+    }
+    if (n & 1 != 0) {
+        d[0] = s[0];
+    }
+    return dest;
+}

crates/compiler/builtins/bitcode/src/main.zig

@@ -7,6 +7,7 @@ const panic_utils = @import("panic.zig");
 
 comptime {
     _ = @import("compiler_rt.zig");
+    _ = @import("libc.zig");
 }
 
 const ROC_BUILTINS = "roc_builtins";

crates/compiler/builtins/bitcode/src/utils.zig

@@ -19,9 +19,6 @@ extern fn roc_realloc(c_ptr: *anyopaque, new_size: usize, old_size: usize, align
 // This should never be passed a null pointer.
 extern fn roc_dealloc(c_ptr: *anyopaque, alignment: u32) callconv(.C) void;
 
-// should work just like libc memcpy (we can't assume libc is present)
-extern fn roc_memcpy(dst: [*]u8, src: [*]u8, size: usize) callconv(.C) void;
-
 extern fn kill(pid: c_int, sig: c_int) c_int;
 extern fn shm_open(name: *const i8, oflag: c_int, mode: c_uint) c_int;
 extern fn mmap(addr: ?*anyopaque, length: c_uint, prot: c_int, flags: c_int, fd: c_int, offset: c_uint) *anyopaque;
@@ -49,7 +46,6 @@ comptime {
         @export(testing_roc_realloc, .{ .name = "roc_realloc", .linkage = .Strong });
         @export(testing_roc_dealloc, .{ .name = "roc_dealloc", .linkage = .Strong });
         @export(testing_roc_panic, .{ .name = "roc_panic", .linkage = .Strong });
-        @export(testing_roc_memcpy, .{ .name = "roc_memcpy", .linkage = .Strong });
 
         if (builtin.os.tag == .macos or builtin.os.tag == .linux) {
             @export(testing_roc_getppid, .{ .name = "roc_getppid", .linkage = .Strong });
@@ -83,14 +79,6 @@ fn testing_roc_panic(c_ptr: *anyopaque, tag_id: u32) callconv(.C) void {
     @panic("Roc panicked");
 }
 
-fn testing_roc_memcpy(dest: *anyopaque, src: *anyopaque, bytes: usize) callconv(.C) ?*anyopaque {
-    const zig_dest = @ptrCast([*]u8, dest);
-    const zig_src = @ptrCast([*]u8, src);
-
-    @memcpy(zig_dest, zig_src, bytes);
-    return dest;
-}
-
 pub fn alloc(size: usize, alignment: u32) ?[*]u8 {
     return @ptrCast(?[*]u8, roc_alloc(size, alignment));
 }
@@ -103,10 +91,6 @@ pub fn dealloc(c_ptr: [*]u8, alignment: u32) void {
     return roc_dealloc(c_ptr, alignment);
 }
 
-pub fn memcpy(dst: [*]u8, src: [*]u8, size: usize) void {
-    roc_memcpy(dst, src, size);
-}
-
 // indirection because otherwise zig creates an alias to the panic function which our LLVM code
 // does not know how to deal with
 pub fn test_panic(c_ptr: *anyopaque, crash_tag: u32) callconv(.C) void {

crates/compiler/can/src/env.rs

@@ -124,18 +124,19 @@ impl<'a> Env<'a> {
                     Ok(symbol)
                 }
                 None => {
-                    let error = RuntimeError::LookupNotInScope(
+                    let error = RuntimeError::LookupNotInScope {
-                        Loc {
+                        loc_name: Loc {
                             value: Ident::from(ident),
                             region,
                         },
-                        scope
+                        suggestion_options: scope
                             .locals
                             .ident_ids
                             .ident_strs()
                             .map(|(_, string)| string.into())
                             .collect(),
-                    );
+                        underscored_suggestion_region: None,
+                    };
                     Err(error)
                 }
             }

crates/compiler/can/src/expr.rs

@@ -1019,9 +1019,18 @@ pub fn canonicalize_expr<'a>(
         }
         ast::Expr::Underscore(name) => {
             // we parse underscores, but they are not valid expression syntax
+
             let problem = roc_problem::can::RuntimeError::MalformedIdentifier(
                 (*name).into(),
-                roc_parse::ident::BadIdent::Underscore(region.start()),
+                if name.is_empty() {
+                    roc_parse::ident::BadIdent::UnderscoreAlone(region.start())
+                } else {
+                    roc_parse::ident::BadIdent::UnderscoreAtStart {
+                        position: region.start(),
+                        // Check if there's an ignored identifier with this name in scope (for better error messages)
+                        declaration_region: scope.lookup_ignored_local(name),
+                    }
+                },
                 region,
             );
 

crates/compiler/can/src/pattern.rs

@@ -379,6 +379,12 @@ pub fn canonicalize_pattern<'a>(
                 Err(pattern) => pattern,
             }
         }
+        Underscore(name) => {
+            // An underscored identifier can't be used, but we'll still add it to the scope
+            // for better error messages if someone tries to use it.
+            scope.introduce_ignored_local(name, region);
+            Pattern::Underscore
+        }
         Tag(name) => {
             // Canonicalize the tag's name.
             Pattern::AppliedTag {
@@ -479,8 +485,6 @@ pub fn canonicalize_pattern<'a>(
             ptype => unsupported_pattern(env, ptype, region),
         },
 
-        Underscore(_) => Pattern::Underscore,
-
         &NumLiteral(str) => match pattern_type {
             WhenBranch => match finish_parsing_num(str) {
                 Err(_error) => {

crates/compiler/can/src/scope.rs

@@ -41,6 +41,10 @@ pub struct Scope {
 
     /// Identifiers that are in scope, and defined in the current module
     pub locals: ScopedIdentIds,
+
+    /// Ignored variables (variables that start with an underscore).
+    /// We won't intern them because they're only used during canonicalization for error reporting.
+    ignored_locals: VecMap<String, Region>,
 }
 
 impl Scope {
@@ -65,6 +69,7 @@ impl Scope {
             abilities_store: starting_abilities_store,
             shadows: VecMap::default(),
             imports: default_imports,
+            ignored_locals: VecMap::default(),
         }
     }
 
@@ -89,13 +94,17 @@ impl Scope {
         match self.scope_contains_ident(ident) {
             InScope(symbol, _) => Ok(symbol),
             NotInScope(_) | NotPresent => {
-                let error = RuntimeError::LookupNotInScope(
+                // identifier not found
-                    Loc {
+
+                let error = RuntimeError::LookupNotInScope {
+                    loc_name: Loc {
                         region,
                         value: Ident::from(ident),
                     },
-                    self.idents_in_scope().map(|v| v.as_ref().into()).collect(),
+                    suggestion_options: self.idents_in_scope().map(|v| v.as_ref().into()).collect(),
-                );
+                    // Check if the user just forgot to remove an underscore from an ignored identifier
+                    underscored_suggestion_region: self.lookup_ignored_local(ident),
+                };
 
                 Err(error)
             }
@@ -418,11 +427,13 @@ impl Scope {
         // - exposed_ident_count: unchanged
         // - home: unchanged
         let aliases_count = self.aliases.len();
+        let ignored_locals_count = self.ignored_locals.len();
         let locals_snapshot = self.locals.in_scope.len();
 
         let result = f(self);
 
         self.aliases.truncate(aliases_count);
+        self.ignored_locals.truncate(ignored_locals_count);
 
         // anything added in the inner scope is no longer in scope now
         for i in locals_snapshot..self.locals.in_scope.len() {
@@ -444,6 +455,19 @@ impl Scope {
     pub fn gen_unique_symbol(&mut self) -> Symbol {
         Symbol::new(self.home, self.locals.gen_unique())
     }
+
+    /// Introduce a new ignored variable (variable starting with an underscore).
+    /// The underscore itself should not be included in `ident`.
+    pub fn introduce_ignored_local(&mut self, ident: &str, region: Region) {
+        self.ignored_locals.insert(ident.to_owned(), region);
+    }
+
+    /// Lookup an ignored variable (variable starting with an underscore).
+    /// The underscore itself should not be included in `ident`.
+    /// Returns the source code region of the ignored variable if it's found.
+    pub fn lookup_ignored_local(&self, ident: &str) -> Option<Region> {
+        self.ignored_locals.get(&ident.to_owned()).copied()
+    }
 }
 
 pub fn create_alias(

crates/compiler/can/tests/test_can.rs

@@ -332,7 +332,7 @@ mod test_can {
             matches!(
                 problem,
                 Problem::SignatureDefMismatch { .. }
-                    | Problem::RuntimeError(RuntimeError::LookupNotInScope(_, _))
+                    | Problem::RuntimeError(RuntimeError::LookupNotInScope { .. })
             )
         }));
     }
@@ -360,7 +360,7 @@ mod test_can {
             matches!(
                 problem,
                 Problem::SignatureDefMismatch { .. }
-                    | Problem::RuntimeError(RuntimeError::LookupNotInScope(_, _))
+                    | Problem::RuntimeError(RuntimeError::LookupNotInScope { .. })
             )
         }));
     }

crates/compiler/fmt/src/spaces.rs

@@ -761,7 +761,15 @@ fn remove_spaces_bad_ident(ident: BadIdent) -> BadIdent {
     match ident {
         BadIdent::Start(_) => BadIdent::Start(Position::zero()),
         BadIdent::Space(e, _) => BadIdent::Space(e, Position::zero()),
-        BadIdent::Underscore(_) => BadIdent::Underscore(Position::zero()),
+        BadIdent::UnderscoreAlone(_) => BadIdent::UnderscoreAlone(Position::zero()),
+        BadIdent::UnderscoreInMiddle(_) => BadIdent::UnderscoreInMiddle(Position::zero()),
+        BadIdent::UnderscoreAtStart {
+            position: _,
+            declaration_region,
+        } => BadIdent::UnderscoreAtStart {
+            position: Position::zero(),
+            declaration_region,
+        },
         BadIdent::QualifiedTag(_) => BadIdent::QualifiedTag(Position::zero()),
         BadIdent::WeirdAccessor(_) => BadIdent::WeirdAccessor(Position::zero()),
         BadIdent::WeirdDotAccess(_) => BadIdent::WeirdDotAccess(Position::zero()),

crates/compiler/gen_llvm/src/llvm/build.rs

@@ -2859,7 +2859,15 @@ pub fn build_exp_stmt<'a, 'ctx>(
 
                         _ if lay.is_refcounted() => {
                             if value.is_pointer_value() {
-                                let value_ptr = value.into_pointer_value();
+                                let value_ptr = match lay.repr {
+                                    LayoutRepr::Union(union_layout)
+                                        if union_layout
+                                            .stores_tag_id_in_pointer(env.target_info) =>
+                                    {
+                                        tag_pointer_clear_tag_id(env, value.into_pointer_value())
+                                    }
+                                    _ => value.into_pointer_value(),
+                                };
 
                                 let then_block = env.context.append_basic_block(parent, "then");
                                 let done_block = env.context.append_basic_block(parent, "done");

crates/compiler/gen_wasm/src/lib.rs

@@ -289,11 +289,6 @@ mod dummy_platform_functions {
         unimplemented!("It is not valid to call roc panic from within the compiler. Please use the \"platform\" feature if this is a platform.")
     }
 
-    #[no_mangle]
-    pub fn roc_memcpy(_dst: *mut c_void, _src: *mut c_void, _n: usize) -> *mut c_void {
-        unimplemented!("It is not valid to call roc memcpy from within the compiler. Please use the \"platform\" feature if this is a platform.")
-    }
-
     #[no_mangle]
     pub fn roc_memset(_dst: *mut c_void, _c: i32, _n: usize) -> *mut c_void {
         unimplemented!("It is not valid to call roc memset from within the compiler. Please use the \"platform\" feature if this is a platform.")

crates/compiler/load_internal/src/file.rs

@@ -53,6 +53,8 @@ use roc_parse::module::module_defs;
 use roc_parse::parser::{FileError, Parser, SourceError, SyntaxError};
 use roc_problem::Severity;
 use roc_region::all::{LineInfo, Loc, Region};
+#[cfg(not(target_family = "wasm"))]
+use roc_reporting::report::to_https_problem_report_string;
 use roc_reporting::report::{to_file_problem_report_string, Palette, RenderTarget};
 use roc_solve::module::{extract_module_owned_implementations, Solved, SolvedModule};
 use roc_solve_problem::TypeError;
@@ -72,7 +74,7 @@ use std::{env, fs};
 #[cfg(not(target_family = "wasm"))]
 use {
     roc_packaging::cache::{self},
-    roc_packaging::https::PackageMetadata,
+    roc_packaging::https::{PackageMetadata, Problem},
 };
 
 pub use crate::work::Phase;
@@ -2454,11 +2456,11 @@ fn update<'a>(
                                     }
                                 }
                                 Err(url_err) => {
-                                    todo!(
+                                    let buf = to_https_problem_report_string(
-                                        "Gracefully report URL error for {:?} - {:?}",
                                         url,
-                                        url_err
+                                        Problem::InvalidUrl(url_err),
                                     );
+                                    return Err(LoadingProblem::FormattedReport(buf));
                                 }
                             }
                         }
@@ -4329,17 +4331,22 @@ fn load_packages<'a>(
                 // TODO we should do this async; however, with the current
                 // architecture of file.rs (which doesn't use async/await),
                 // this would be very difficult!
-                let (package_dir, opt_root_module) = cache::install_package(roc_cache_dir, src)
+                match cache::install_package(roc_cache_dir, src) {
-                    .unwrap_or_else(|err| {
+                    Ok((package_dir, opt_root_module)) => {
-                        todo!("TODO gracefully handle package install error {:?}", err);
+                        // You can optionally specify the root module using the URL fragment,
-                    });
+                        // e.g. #foo.roc
+                        // (defaults to main.roc)
+                        match opt_root_module {
+                            Some(root_module) => package_dir.join(root_module),
+                            None => package_dir.join("main.roc"),
+                        }
+                    }
+                    Err(problem) => {
+                        let buf = to_https_problem_report_string(src, problem);
 
-                // You can optionally specify the root module using the URL fragment,
+                        load_messages.push(Msg::FailedToLoad(LoadingProblem::FormattedReport(buf)));
-                // e.g. #foo.roc
+                        return;
-                // (defaults to main.roc)
+                    }
-                match opt_root_module {
-                    Some(root_module) => package_dir.join(root_module),
-                    None => package_dir.join("main.roc"),
                 }
             }
 

crates/compiler/parse/src/ident.rs

@@ -3,7 +3,7 @@ use crate::parser::{BadInputError, EExpr, ParseResult, Parser};
 use crate::state::State;
 use bumpalo::collections::vec::Vec;
 use bumpalo::Bump;
-use roc_region::all::Position;
+use roc_region::all::{Position, Region};
 
 /// A tag, for example. Must start with an uppercase letter
 /// and then contain only letters and numbers afterwards - no dots allowed!
@@ -254,7 +254,14 @@ pub enum BadIdent {
     Start(Position),
     Space(BadInputError, Position),
 
-    Underscore(Position),
+    UnderscoreAlone(Position),
+    UnderscoreInMiddle(Position),
+    UnderscoreAtStart {
+        position: Position,
+        /// If this variable was already declared in a pattern (e.g. \_x -> _x),
+        /// then this is where it was declared.
+        declaration_region: Option<Region>,
+    },
     QualifiedTag(Position),
     WeirdAccessor(Position),
     WeirdDotAccess(Position),
@@ -529,7 +536,7 @@ fn chomp_identifier_chain<'a>(
         // to give good error messages for this case
         Err((
             chomped as u32 + 1,
-            BadIdent::Underscore(pos.bump_column(chomped as u32 + 1)),
+            BadIdent::UnderscoreInMiddle(pos.bump_column(chomped as u32 + 1)),
         ))
     } else if first_is_uppercase {
         // just one segment, starting with an uppercase letter; that's a tag

crates/compiler/problem/src/can.rs

@@ -335,7 +335,11 @@ impl Problem {
             })
             | Problem::RuntimeError(RuntimeError::UnsupportedPattern(region))
             | Problem::RuntimeError(RuntimeError::MalformedPattern(_, region))
-            | Problem::RuntimeError(RuntimeError::LookupNotInScope(Loc { region, .. }, _))
+            | Problem::RuntimeError(RuntimeError::LookupNotInScope {
+                loc_name: Loc { region, .. },
+                suggestion_options: _,
+                underscored_suggestion_region: _,
+            })
             | Problem::RuntimeError(RuntimeError::OpaqueNotDefined {
                 usage: Loc { region, .. },
                 ..
@@ -505,7 +509,14 @@ pub enum RuntimeError {
     UnresolvedTypeVar,
     ErroneousType,
 
-    LookupNotInScope(Loc<Ident>, MutSet<Box<str>>),
+    LookupNotInScope {
+        loc_name: Loc<Ident>,
+        /// All of the names in scope (for the error message)
+        suggestion_options: MutSet<Box<str>>,
+        /// If the unfound variable is `name` and there's an ignored variable called `_name`,
+        /// this is the region where `_name` is defined (for the error message)
+        underscored_suggestion_region: Option<Region>,
+    },
     OpaqueNotDefined {
         usage: Loc<Ident>,
         opaques_in_scope: MutSet<Box<str>>,

crates/compiler/test_gen/src/gen_tags.rs

@@ -14,6 +14,8 @@ use roc_mono::layout::{LayoutRepr, STLayoutInterner};
 #[cfg(test)]
 use roc_std::{RocList, RocStr, U128};
 
+use crate::helpers::with_larger_debug_stack;
+
 #[test]
 fn width_and_alignment_u8_u8() {
     use roc_mono::layout::Layout;
@@ -2167,27 +2169,29 @@ fn refcount_nullable_unwrapped_needing_no_refcount_issue_5027() {
 #[test]
 #[cfg(any(feature = "gen-llvm"))]
 fn issue_5162_recast_nested_nullable_unwrapped_layout() {
-    assert_evals_to!(
+    with_larger_debug_stack(|| {
-        indoc!(
+        assert_evals_to!(
-            r###"
+            indoc!(
-            app "test" provides [main] to "./platform"
+                r###"
+                app "test" provides [main] to "./platform"
 
-            Concept : [
+                Concept : [
-                AtomicConcept,
+                    AtomicConcept,
-                ExistentialRestriction { role : Str, concept : Concept }
+                    ExistentialRestriction { role : Str, concept : Concept }
-            ]
+                ]
 
-            bottom : Concept
+                bottom : Concept
-            bottom = AtomicConcept
+                bottom = AtomicConcept
 
-            main =
+                main =
-                when Dict.single bottom 0 is
+                    when Dict.single bottom 0 is
-                    _ -> Bool.true
+                        _ -> Bool.true
-            "###
+                "###
-        ),
+            ),
-        true,
+            true,
-        bool
+            bool
-    );
+        );
+    });
 }
 
 #[test]

crates/compiler/test_gen/src/helpers/platform_functions.rs

@@ -7,13 +7,6 @@ pub unsafe fn roc_alloc(size: usize, _alignment: u32) -> *mut c_void {
     libc::malloc(size)
 }
 
-/// # Safety
-/// The Roc application needs this.
-#[no_mangle]
-pub unsafe fn roc_memcpy(dest: *mut c_void, src: *const c_void, bytes: usize) -> *mut c_void {
-    libc::memcpy(dest, src, bytes)
-}
-
 /// # Safety
 /// The Roc application needs this.
 #[no_mangle]

crates/compiler/test_gen/src/helpers/wasm_test_platform.c

@@ -134,13 +134,6 @@ void roc_panic(void* msg, unsigned int tag_id)
 
 //--------------------------
 
-void roc_memcpy(void *dest, const void *src, size_t n)
-{
-    memcpy(dest, src, n);
-}
-
-//--------------------------
-
 void *roc_memset(void *str, int c, size_t n)
 {
     return memset(str, c, n);

crates/compiler/test_syntax/tests/snapshots/malformed/malformed_ident_due_to_underscore.expr.result-ast

@@ -2,7 +2,7 @@ Closure(
     [
         @1-11 MalformedIdent(
             "the_answer",
-            Underscore(
+            UnderscoreInMiddle(
                 @5,
             ),
         ),

crates/compiler/test_syntax/tests/snapshots/malformed/underscore_expr_in_def.expr.result-ast

@@ -31,7 +31,7 @@ Defs(
     @5-8 SpaceBefore(
         MalformedIdent(
             "n_p",
-            Underscore(
+            UnderscoreInMiddle(
                 @7,
             ),
         ),

crates/glue/tests/fixtures/advanced-recursive-union/src/lib.rs

@@ -78,11 +78,6 @@ pub unsafe extern "C" fn roc_panic(c_ptr: *mut c_void, tag_id: u32) {
     }
 }
 
-#[no_mangle]
-pub unsafe extern "C" fn roc_memcpy(dst: *mut c_void, src: *mut c_void, n: usize) -> *mut c_void {
-    libc::memcpy(dst, src, n)
-}
-
 #[no_mangle]
 pub unsafe extern "C" fn roc_memset(dst: *mut c_void, c: i32, n: usize) -> *mut c_void {
     libc::memset(dst, c, n)

crates/glue/tests/fixtures/arguments/src/lib.rs

@@ -49,11 +49,6 @@ pub unsafe extern "C" fn roc_panic(c_ptr: *mut c_void, tag_id: u32) {
     }
 }
 
-#[no_mangle]
-pub unsafe extern "C" fn roc_memcpy(dst: *mut c_void, src: *mut c_void, n: usize) -> *mut c_void {
-    libc::memcpy(dst, src, n)
-}
-
 #[no_mangle]
 pub unsafe extern "C" fn roc_memset(dst: *mut c_void, c: i32, n: usize) -> *mut c_void {
     libc::memset(dst, c, n)

crates/glue/tests/fixtures/basic-record/src/lib.rs

@@ -71,11 +71,6 @@ pub unsafe extern "C" fn roc_panic(c_ptr: *mut c_void, tag_id: u32) {
     }
 }
 
-#[no_mangle]
-pub unsafe extern "C" fn roc_memcpy(dst: *mut c_void, src: *mut c_void, n: usize) -> *mut c_void {
-    libc::memcpy(dst, src, n)
-}
-
 #[no_mangle]
 pub unsafe extern "C" fn roc_memset(dst: *mut c_void, c: i32, n: usize) -> *mut c_void {
     libc::memset(dst, c, n)

crates/glue/tests/fixtures/basic-recursive-union/src/lib.rs

@@ -13,7 +13,7 @@ pub extern "C" fn rust_main() -> i32 {
     use std::cmp::Ordering;
     use std::collections::hash_set::HashSet;
 
-    let tag_union = test_glue::mainForHost(()); 
+    let tag_union = test_glue::mainForHost(());
 
     // Verify that it has all the expected traits.
 
@@ -89,11 +89,6 @@ pub unsafe extern "C" fn roc_panic(c_ptr: *mut c_void, tag_id: u32) {
     }
 }
 
-#[no_mangle]
-pub unsafe extern "C" fn roc_memcpy(dst: *mut c_void, src: *mut c_void, n: usize) -> *mut c_void {
-    libc::memcpy(dst, src, n)
-}
-
 #[no_mangle]
 pub unsafe extern "C" fn roc_memset(dst: *mut c_void, c: i32, n: usize) -> *mut c_void {
     libc::memset(dst, c, n)

crates/glue/tests/fixtures/enumeration/src/lib.rs

@@ -75,11 +75,6 @@ pub unsafe extern "C" fn roc_panic(c_ptr: *mut c_void, tag_id: u32) {
     }
 }
 
-#[no_mangle]
-pub unsafe extern "C" fn roc_memcpy(dst: *mut c_void, src: *mut c_void, n: usize) -> *mut c_void {
-    libc::memcpy(dst, src, n)
-}
-
 #[no_mangle]
 pub unsafe extern "C" fn roc_memset(dst: *mut c_void, c: i32, n: usize) -> *mut c_void {
     libc::memset(dst, c, n)

crates/glue/tests/fixtures/list-recursive-union/src/lib.rs

@@ -88,11 +88,6 @@ pub unsafe extern "C" fn roc_panic(c_ptr: *mut c_void, tag_id: u32) {
     }
 }
 
-#[no_mangle]
-pub unsafe extern "C" fn roc_memcpy(dst: *mut c_void, src: *mut c_void, n: usize) -> *mut c_void {
-    libc::memcpy(dst, src, n)
-}
-
 #[no_mangle]
 pub unsafe extern "C" fn roc_memset(dst: *mut c_void, c: i32, n: usize) -> *mut c_void {
     libc::memset(dst, c, n)

crates/glue/tests/fixtures/multiple-modules/src/lib.rs

@@ -76,11 +76,6 @@ pub unsafe extern "C" fn roc_panic(c_ptr: *mut c_void, tag_id: u32) {
     }
 }
 
-#[no_mangle]
-pub unsafe extern "C" fn roc_memcpy(dst: *mut c_void, src: *mut c_void, n: usize) -> *mut c_void {
-    libc::memcpy(dst, src, n)
-}
-
 #[no_mangle]
 pub unsafe extern "C" fn roc_memset(dst: *mut c_void, c: i32, n: usize) -> *mut c_void {
     libc::memset(dst, c, n)

crates/glue/tests/fixtures/nested-record/src/lib.rs

@@ -73,11 +73,6 @@ pub unsafe extern "C" fn roc_panic(c_ptr: *mut c_void, tag_id: u32) {
     }
 }
 
-#[no_mangle]
-pub unsafe extern "C" fn roc_memcpy(dst: *mut c_void, src: *mut c_void, n: usize) -> *mut c_void {
-    libc::memcpy(dst, src, n)
-}
-
 #[no_mangle]
 pub unsafe extern "C" fn roc_memset(dst: *mut c_void, c: i32, n: usize) -> *mut c_void {
     libc::memset(dst, c, n)

crates/glue/tests/fixtures/nonnullable-unwrapped/src/lib.rs

@@ -91,11 +91,6 @@ pub unsafe extern "C" fn roc_panic(c_ptr: *mut c_void, tag_id: u32) {
     }
 }
 
-#[no_mangle]
-pub unsafe extern "C" fn roc_memcpy(dst: *mut c_void, src: *mut c_void, n: usize) -> *mut c_void {
-    libc::memcpy(dst, src, n)
-}
-
 #[no_mangle]
 pub unsafe extern "C" fn roc_memset(dst: *mut c_void, c: i32, n: usize) -> *mut c_void {
     libc::memset(dst, c, n)

crates/glue/tests/fixtures/nullable-unwrapped/src/lib.rs

@@ -87,11 +87,6 @@ pub unsafe extern "C" fn roc_panic(c_ptr: *mut c_void, tag_id: u32) {
     }
 }
 
-#[no_mangle]
-pub unsafe extern "C" fn roc_memcpy(dst: *mut c_void, src: *mut c_void, n: usize) -> *mut c_void {
-    libc::memcpy(dst, src, n)
-}
-
 #[no_mangle]
 pub unsafe extern "C" fn roc_memset(dst: *mut c_void, c: i32, n: usize) -> *mut c_void {
     libc::memset(dst, c, n)

crates/glue/tests/fixtures/nullable-wrapped/src/lib.rs

@@ -102,11 +102,6 @@ pub unsafe extern "C" fn roc_panic(c_ptr: *mut c_void, tag_id: u32) {
     }
 }
 
-#[no_mangle]
-pub unsafe extern "C" fn roc_memcpy(dst: *mut c_void, src: *mut c_void, n: usize) -> *mut c_void {
-    libc::memcpy(dst, src, n)
-}
-
 #[no_mangle]
 pub unsafe extern "C" fn roc_memset(dst: *mut c_void, c: i32, n: usize) -> *mut c_void {
     libc::memset(dst, c, n)

crates/glue/tests/fixtures/option/src/lib.rs

@@ -51,11 +51,6 @@ pub unsafe extern "C" fn roc_panic(c_ptr: *mut c_void, tag_id: u32) {
     }
 }
 
-#[no_mangle]
-pub unsafe extern "C" fn roc_memcpy(dst: *mut c_void, src: *mut c_void, n: usize) -> *mut c_void {
-    libc::memcpy(dst, src, n)
-}
-
 #[no_mangle]
 pub unsafe extern "C" fn roc_memset(dst: *mut c_void, c: i32, n: usize) -> *mut c_void {
     libc::memset(dst, c, n)

crates/glue/tests/fixtures/return-function/src/lib.rs

@@ -51,11 +51,6 @@ pub unsafe extern "C" fn roc_panic(c_ptr: *mut c_void, tag_id: u32) {
     }
 }
 
-#[no_mangle]
-pub unsafe extern "C" fn roc_memcpy(dst: *mut c_void, src: *mut c_void, n: usize) -> *mut c_void {
-    libc::memcpy(dst, src, n)
-}
-
 #[no_mangle]
 pub unsafe extern "C" fn roc_memset(dst: *mut c_void, c: i32, n: usize) -> *mut c_void {
     libc::memset(dst, c, n)

crates/glue/tests/fixtures/rocresult/src/lib.rs

@@ -51,11 +51,6 @@ pub unsafe extern "C" fn roc_panic(c_ptr: *mut c_void, tag_id: u32) {
     }
 }
 
-#[no_mangle]
-pub unsafe extern "C" fn roc_memcpy(dst: *mut c_void, src: *mut c_void, n: usize) -> *mut c_void {
-    libc::memcpy(dst, src, n)
-}
-
 #[no_mangle]
 pub unsafe extern "C" fn roc_memset(dst: *mut c_void, c: i32, n: usize) -> *mut c_void {
     libc::memset(dst, c, n)

crates/glue/tests/fixtures/single-tag-union/src/lib.rs

@@ -77,11 +77,6 @@ pub unsafe extern "C" fn roc_panic(c_ptr: *mut c_void, tag_id: u32) {
     }
 }
 
-#[no_mangle]
-pub unsafe extern "C" fn roc_memcpy(dst: *mut c_void, src: *mut c_void, n: usize) -> *mut c_void {
-    libc::memcpy(dst, src, n)
-}
-
 #[no_mangle]
 pub unsafe extern "C" fn roc_memset(dst: *mut c_void, c: i32, n: usize) -> *mut c_void {
     libc::memset(dst, c, n)

crates/glue/tests/fixtures/union-with-padding/src/lib.rs

@@ -82,11 +82,6 @@ pub unsafe extern "C" fn roc_panic(c_ptr: *mut c_void, tag_id: u32) {
     }
 }
 
-#[no_mangle]
-pub unsafe extern "C" fn roc_memcpy(dst: *mut c_void, src: *mut c_void, n: usize) -> *mut c_void {
-    libc::memcpy(dst, src, n)
-}
-
 #[no_mangle]
 pub unsafe extern "C" fn roc_memset(dst: *mut c_void, c: i32, n: usize) -> *mut c_void {
     libc::memset(dst, c, n)

crates/glue/tests/fixtures/union-without-padding/src/lib.rs

@@ -79,11 +79,6 @@ pub unsafe extern "C" fn roc_panic(c_ptr: *mut c_void, tag_id: u32) {
     }
 }
 
-#[no_mangle]
-pub unsafe extern "C" fn roc_memcpy(dst: *mut c_void, src: *mut c_void, n: usize) -> *mut c_void {
-    libc::memcpy(dst, src, n)
-}
-
 #[no_mangle]
 pub unsafe extern "C" fn roc_memset(dst: *mut c_void, c: i32, n: usize) -> *mut c_void {
     libc::memset(dst, c, n)

crates/linker/src/elf.rs

@@ -140,7 +140,6 @@ fn collect_roc_definitions<'a>(object: &object::File<'a, &'a [u8]>) -> MutMap<St
 
         // special exceptions for roc_ functions that map to libc symbols
         let direct_mapping = match name {
-            "roc_memcpy" => Some("memcpy"),
             "roc_memset" => Some("memset"),
             "roc_memmove" => Some("memmove"),
 
@@ -603,7 +602,7 @@ fn gen_elf_le(
     }
 
     // Copy header and shift everything to enable more program sections.
-    let added_header_count = 2;
+    let added_header_count = 3;
     md.added_byte_count = ph_ent_size as u64 * added_header_count;
     md.added_byte_count = md.added_byte_count
         + (MIN_SECTION_ALIGNMENT as u64 - md.added_byte_count % MIN_SECTION_ALIGNMENT as u64);
@@ -1278,22 +1277,12 @@ fn surgery_elf_help(
     let mut offset = sh_offset as usize;
     offset = align_by_constraint(offset, MIN_SECTION_ALIGNMENT);
 
-    let new_rodata_section_offset = offset;
-
     // Align physical and virtual address of new segment.
     let mut virt_offset = align_to_offset_by_constraint(
         md.last_vaddr as usize,
         offset,
         md.load_align_constraint as usize,
     );
-    let new_rodata_section_vaddr = virt_offset;
-    if verbose {
-        println!();
-        println!(
-            "New Virtual Rodata Section Address: {:+x?}",
-            new_rodata_section_vaddr
-        );
-    }
 
     // First decide on sections locations and then recode every exact symbol locations.
 
@@ -1375,13 +1364,40 @@ fn surgery_elf_help(
         println!("Found App Function Symbols: {:+x?}", app_func_vaddr_map);
     }
 
+    let (new_rodata_section_offset, new_rodata_section_vaddr) = rodata_sections
+        .iter()
+        .map(|sec| section_offset_map.get(&sec.index()).unwrap())
+        .min()
+        .unwrap();
+    let (new_rodata_section_offset, new_rodata_section_vaddr) = (
+        *new_rodata_section_offset as u64,
+        *new_rodata_section_vaddr as u64,
+    );
     let (new_text_section_offset, new_text_section_vaddr) = text_sections
         .iter()
         .map(|sec| section_offset_map.get(&sec.index()).unwrap())
         .min()
         .unwrap();
-    let (new_text_section_offset, new_text_section_vaddr) =
+    let (new_text_section_offset, new_text_section_vaddr) = (
-        (*new_text_section_offset, *new_text_section_vaddr);
+        *new_text_section_offset as u64,
+        *new_text_section_vaddr as u64,
+    );
+    // BSS section is not guaranteed to exist.
+    // If it doesn't exist, just use the text section offset.
+    // This will make a bss section of size 0.
+    let bss_default = (
+        new_text_section_offset as usize,
+        new_text_section_vaddr as usize,
+    );
+    let (new_bss_section_offset, new_bss_section_vaddr) = bss_sections
+        .iter()
+        .map(|sec| section_offset_map.get(&sec.index()).unwrap())
+        .min()
+        .unwrap_or(&bss_default);
+    let (new_bss_section_offset, new_bss_section_vaddr) = (
+        *new_bss_section_offset as u64,
+        *new_bss_section_vaddr as u64,
+    );
 
     // Move data and deal with relocations.
     for sec in rodata_sections
@@ -1494,15 +1510,15 @@ fn surgery_elf_help(
     // Flush app only data to speed up write to disk.
     exec_mmap
         .flush_async_range(
-            new_rodata_section_offset,
+            new_rodata_section_offset as usize,
-            offset - new_rodata_section_offset,
+            offset - new_rodata_section_offset as usize,
         )
         .unwrap_or_else(|e| internal_error!("{}", e));
 
     // TODO: look into merging symbol tables, debug info, and eh frames to enable better debugger experience.
 
-    // Add 2 new sections and segments.
+    // Add 3 new sections and segments.
-    let new_section_count = 2;
+    let new_section_count = 3;
     offset += new_section_count * sh_ent_size as usize;
     let section_headers = load_structs_inplace_mut::<elf::SectionHeader64<LE>>(
         exec_mmap,
@@ -1510,19 +1526,17 @@ fn surgery_elf_help(
         sh_num as usize + new_section_count,
     );
 
-    let new_rodata_section_size = new_text_section_offset as u64 - new_rodata_section_offset as u64;
+    let new_rodata_section_size = new_text_section_offset - new_rodata_section_offset;
-    let new_rodata_section_virtual_size =
+    let new_bss_section_virtual_size = new_text_section_vaddr - new_bss_section_vaddr;
-        new_text_section_vaddr as u64 - new_rodata_section_vaddr as u64;
+    let new_text_section_size = new_sh_offset as u64 - new_text_section_offset;
-    let new_text_section_vaddr = new_rodata_section_vaddr as u64 + new_rodata_section_size;
-    let new_text_section_size = new_sh_offset as u64 - new_text_section_offset as u64;
 
     // set the new rodata section header
-    section_headers[section_headers.len() - 2] = elf::SectionHeader64 {
+    section_headers[section_headers.len() - 3] = elf::SectionHeader64 {
         sh_name: endian::U32::new(LE, 0),
         sh_type: endian::U32::new(LE, elf::SHT_PROGBITS),
         sh_flags: endian::U64::new(LE, elf::SHF_ALLOC as u64),
-        sh_addr: endian::U64::new(LE, new_rodata_section_vaddr as u64),
+        sh_addr: endian::U64::new(LE, new_rodata_section_vaddr),
-        sh_offset: endian::U64::new(LE, new_rodata_section_offset as u64),
+        sh_offset: endian::U64::new(LE, new_rodata_section_offset),
         sh_size: endian::U64::new(LE, new_rodata_section_size),
         sh_link: endian::U32::new(LE, 0),
         sh_info: endian::U32::new(LE, 0),
@@ -1530,13 +1544,27 @@ fn surgery_elf_help(
         sh_entsize: endian::U64::new(LE, 0),
     };
 
+    // set the new bss section header
+    section_headers[section_headers.len() - 2] = elf::SectionHeader64 {
+        sh_name: endian::U32::new(LE, 0),
+        sh_type: endian::U32::new(LE, elf::SHT_NOBITS),
+        sh_flags: endian::U64::new(LE, (elf::SHF_ALLOC) as u64),
+        sh_addr: endian::U64::new(LE, new_bss_section_vaddr),
+        sh_offset: endian::U64::new(LE, new_bss_section_offset),
+        sh_size: endian::U64::new(LE, new_bss_section_virtual_size),
+        sh_link: endian::U32::new(LE, 0),
+        sh_info: endian::U32::new(LE, 0),
+        sh_addralign: endian::U64::new(LE, 16),
+        sh_entsize: endian::U64::new(LE, 0),
+    };
+
     // set the new text section header
     section_headers[section_headers.len() - 1] = elf::SectionHeader64 {
         sh_name: endian::U32::new(LE, 0),
         sh_type: endian::U32::new(LE, elf::SHT_PROGBITS),
         sh_flags: endian::U64::new(LE, (elf::SHF_ALLOC | elf::SHF_EXECINSTR) as u64),
         sh_addr: endian::U64::new(LE, new_text_section_vaddr),
-        sh_offset: endian::U64::new(LE, new_text_section_offset as u64),
+        sh_offset: endian::U64::new(LE, new_text_section_offset),
         sh_size: endian::U64::new(LE, new_text_section_size),
         sh_link: endian::U32::new(LE, 0),
         sh_info: endian::U32::new(LE, 0),
@@ -1559,14 +1587,26 @@ fn surgery_elf_help(
     );
 
     // set the new rodata section program header
-    program_headers[program_headers.len() - 2] = elf::ProgramHeader64 {
+    program_headers[program_headers.len() - 3] = elf::ProgramHeader64 {
         p_type: endian::U32::new(LE, elf::PT_LOAD),
         p_flags: endian::U32::new(LE, elf::PF_R),
-        p_offset: endian::U64::new(LE, new_rodata_section_offset as u64),
+        p_offset: endian::U64::new(LE, new_rodata_section_offset),
-        p_vaddr: endian::U64::new(LE, new_rodata_section_vaddr as u64),
+        p_vaddr: endian::U64::new(LE, new_rodata_section_vaddr),
-        p_paddr: endian::U64::new(LE, new_rodata_section_vaddr as u64),
+        p_paddr: endian::U64::new(LE, new_rodata_section_vaddr),
         p_filesz: endian::U64::new(LE, new_rodata_section_size),
-        p_memsz: endian::U64::new(LE, new_rodata_section_virtual_size),
+        p_memsz: endian::U64::new(LE, new_rodata_section_size),
+        p_align: endian::U64::new(LE, md.load_align_constraint),
+    };
+
+    // set the new bss section program header
+    program_headers[program_headers.len() - 2] = elf::ProgramHeader64 {
+        p_type: endian::U32::new(LE, elf::PT_LOAD),
+        p_flags: endian::U32::new(LE, elf::PF_R | elf::PF_W),
+        p_offset: endian::U64::new(LE, new_bss_section_offset),
+        p_vaddr: endian::U64::new(LE, new_bss_section_vaddr),
+        p_paddr: endian::U64::new(LE, new_bss_section_vaddr),
+        p_filesz: endian::U64::new(LE, 0),
+        p_memsz: endian::U64::new(LE, new_bss_section_virtual_size),
         p_align: endian::U64::new(LE, md.load_align_constraint),
     };
 
@@ -1575,7 +1615,7 @@ fn surgery_elf_help(
     program_headers[new_text_section_index] = elf::ProgramHeader64 {
         p_type: endian::U32::new(LE, elf::PT_LOAD),
         p_flags: endian::U32::new(LE, elf::PF_R | elf::PF_X),
-        p_offset: endian::U64::new(LE, new_text_section_offset as u64),
+        p_offset: endian::U64::new(LE, new_text_section_offset),
         p_vaddr: endian::U64::new(LE, new_text_section_vaddr),
         p_paddr: endian::U64::new(LE, new_text_section_vaddr),
         p_filesz: endian::U64::new(LE, new_text_section_size),
@@ -1722,7 +1762,6 @@ mod tests {
 
         assert_eq!(
             [
-                "memcpy",
                 "memset",
                 "roc_alloc",
                 "roc_dealloc",

crates/linker/src/macho.rs

@@ -141,9 +141,7 @@ fn collect_roc_definitions<'a>(object: &object::File<'a, &'a [u8]>) -> MutMap<St
         let address = sym.address();
 
         // special exceptions for memcpy and memset.
-        if name == "roc_memcpy" {
+        if name == "roc_memset" {
-            vaddresses.insert("memcpy".to_string(), address);
-        } else if name == "roc_memset" {
             vaddresses.insert("memset".to_string(), address);
         }
 

crates/linker/src/pe.rs

@@ -444,6 +444,7 @@ pub(crate) fn surgery_pe(executable_path: &Path, metadata_path: &Path, roc_app_b
                         "__fixsfti",
                         "__fixunsdfti",
                         "__fixunssfti",
+                        "memcpy_decision",
                     ]
                     .contains(&name.as_str());
                     if *address == 0 && !name.starts_with("roc") && !is_ingested_compiler_rt {
@@ -1318,7 +1319,6 @@ fn relocate_dummy_dll_entries(executable: &mut [u8], md: &PeMetadata) {
 /// Redirect `memcpy` and similar libc functions to their roc equivalents
 pub(crate) fn redirect_libc_functions(name: &str) -> Option<&str> {
     match name {
-        "memcpy" => Some("roc_memcpy"),
         "memset" => Some("roc_memset"),
         "memmove" => Some("roc_memmove"),
         _ => None,

crates/repl_wasm/src/repl_platform.c

@@ -64,13 +64,6 @@ void roc_panic(void *ptr, unsigned int alignment)
 
 //--------------------------
 
-void *roc_memcpy(void *dest, const void *src, size_t n)
-{
-    return memcpy(dest, src, n);
-}
-
-//--------------------------
-
 void *roc_memset(void *str, int c, size_t n)
 {
     return memset(str, c, n);

crates/reporting/Cargo.toml

@@ -15,12 +15,14 @@ roc_exhaustive = { path = "../compiler/exhaustive" }
 roc_fmt = { path = "../compiler/fmt" }
 roc_module = { path = "../compiler/module" }
 roc_parse = { path = "../compiler/parse" }
+roc_packaging = { path = "../packaging" }
 roc_problem = { path = "../compiler/problem" }
 roc_region = { path = "../compiler/region" }
 roc_solve_problem = { path = "../compiler/solve_problem" }
 roc_std = { path = "../roc_std" }
 roc_types = { path = "../compiler/types" }
 ven_pretty = { path = "../vendor/pretty" }
+byte-unit = "4.0.19"
 itertools = "0.10.5"
 
 bumpalo.workspace = true

crates/reporting/src/error/canonicalize.rs

@@ -1254,19 +1254,49 @@ fn to_bad_ident_expr_report<'b>(
             ])
         }
 
-        Underscore(pos) => {
+        UnderscoreAlone(_pos) => {
-            let region = Region::new(surroundings.start(), pos);
+            alloc.stack([
+                alloc.reflow("An underscore is being used as a variable here:"),
+                alloc.region(lines.convert_region(surroundings)),
+                alloc.concat([alloc
+                    .reflow(r"An underscore can be used to ignore a value when pattern matching, but it cannot be used as a variable.")]),
+            ])
+        }
+
+        UnderscoreInMiddle(_pos) => {
             alloc.stack([
                 alloc.reflow("Underscores are not allowed in identifier names:"),
-                alloc.region_with_subregion(
+                alloc.region(lines.convert_region(surroundings)),
-                    lines.convert_region(surroundings),
-                    lines.convert_region(region),
-                ),
                 alloc.concat([alloc
                     .reflow(r"I recommend using camelCase. It's the standard style in Roc code!")]),
             ])
         }
 
+        UnderscoreAtStart {
+            position: _pos,
+            declaration_region,
+        } => {
+            let line = "This variable's name starts with an underscore:";
+            alloc.stack([
+                match declaration_region {
+                    None => alloc.reflow(line),
+                    Some(declaration_region) => alloc.stack([
+                        alloc.reflow(line),
+                        alloc.region(lines.convert_region(declaration_region)),
+                        alloc.reflow("But then it is used here:"),
+                    ])
+                },
+                alloc.region(lines.convert_region(surroundings)),
+                alloc.concat([
+                    alloc.reflow(r"A variable's name can only start with an underscore if the variable is unused. "),
+                    match declaration_region {
+                        None => alloc.reflow(r"But it looks like the variable is being used here!"),
+                        Some(_) => alloc.reflow(r"Since you are using this variable, you could remove the underscore from its name in both places."),
+                    }
+                ]),
+            ])
+        }
+
         BadOpaqueRef(pos) => {
             use BadIdentNext::*;
             let kind = "an opaque reference";
@@ -1409,7 +1439,13 @@ fn to_bad_ident_pattern_report<'b>(
             ])
         }
 
-        Underscore(pos) => {
+        UnderscoreAlone(..) | UnderscoreAtStart { .. } => {
+            unreachable!(
+                "it's fine to have an underscore at the beginning of an identifier in a pattern"
+            )
+        }
+
+        UnderscoreInMiddle(pos) => {
             let region = Region::from_pos(pos.sub(1));
 
             alloc.stack([
@@ -1580,8 +1616,19 @@ fn pretty_runtime_error<'b>(
             (title, doc) = report_shadowing(alloc, lines, original_region, shadow, kind);
         }
 
-        RuntimeError::LookupNotInScope(loc_name, options) => {
+        RuntimeError::LookupNotInScope {
-            doc = not_found(alloc, lines, loc_name.region, &loc_name.value, options);
+            loc_name,
+            suggestion_options: options,
+            underscored_suggestion_region,
+        } => {
+            doc = not_found(
+                alloc,
+                lines,
+                loc_name.region,
+                &loc_name.value,
+                options,
+                underscored_suggestion_region,
+            );
             title = UNRECOGNIZED_NAME;
         }
         RuntimeError::CircularDef(entries) => {
@@ -2219,6 +2266,7 @@ fn not_found<'b>(
     region: roc_region::all::Region,
     name: &Ident,
     options: MutSet<Box<str>>,
+    underscored_suggestion_region: Option<Region>,
 ) -> RocDocBuilder<'b> {
     let mut suggestions = suggest::sort(
         name.as_inline_str().as_str(),
@@ -2234,7 +2282,15 @@ fn not_found<'b>(
         alloc.reflow(" missing up-top"),
     ]);
 
-    let default_yes = alloc.reflow("Did you mean one of these?");
+    let default_yes = match underscored_suggestion_region {
+        Some(underscored_region) => alloc.stack([
+            alloc.reflow("There is an ignored identifier of a similar name here:"),
+            alloc.region(lines.convert_region(underscored_region)),
+            alloc.reflow("Did you mean to remove the leading underscore?"),
+            alloc.reflow("If not, did you mean one of these?"),
+        ]),
+        None => alloc.reflow("Did you mean one of these?"),
+    };
 
     let to_details = |no_suggestion_details, yes_suggestion_details| {
         if suggestions.is_empty() {

crates/reporting/src/report.rs

@@ -7,6 +7,11 @@ use std::path::{Path, PathBuf};
 use std::{fmt, io};
 use ven_pretty::{text, BoxAllocator, DocAllocator, DocBuilder, Render, RenderAnnotated};
 
+#[cfg(not(target_family = "wasm"))]
+use byte_unit::Byte;
+#[cfg(not(target_family = "wasm"))]
+use roc_packaging::https::Problem;
+
 pub use crate::error::canonicalize::can_problem;
 pub use crate::error::parse::parse_problem;
 pub use crate::error::r#type::type_problem;
@@ -1075,6 +1080,471 @@ where
     }
 }
 
+#[cfg(not(target_family = "wasm"))]
+pub fn to_https_problem_report_string(url: &str, https_problem: Problem) -> String {
+    let src_lines: Vec<&str> = Vec::new();
+
+    let mut module_ids = ModuleIds::default();
+
+    let module_id = module_ids.get_or_insert(&"find module name somehow?".into());
+
+    let interns = Interns::default();
+
+    // Report parsing and canonicalization problems
+    let alloc = RocDocAllocator::new(&src_lines, module_id, &interns);
+
+    let mut buf = String::new();
+    let palette = DEFAULT_PALETTE;
+    let report = to_https_problem_report(&alloc, url, https_problem);
+    report.render_color_terminal(&mut buf, &alloc, &palette);
+
+    buf
+}
+
+#[cfg(not(target_family = "wasm"))]
+pub fn to_https_problem_report<'b>(
+    alloc: &'b RocDocAllocator<'b>,
+    url: &'b str,
+    https_problem: Problem,
+) -> Report<'b> {
+    match https_problem {
+        Problem::UnsupportedEncoding(not_supported_encoding) => {
+            let doc = alloc.stack([
+                alloc.reflow(r"I was trying to download this URL:"),
+                alloc.string((&url).to_string()).annotate(Annotation::Url).indent(4),
+                alloc.concat([
+                    alloc.reflow(r"But the server replied with a "),
+                    alloc.reflow(r"content encoding").annotate(Annotation::Emphasized),
+                    alloc.reflow(r" that I do not understand ("),
+                    alloc.string(not_supported_encoding).annotate(Annotation::Emphasized),
+                    alloc.reflow(r")."),
+                ]),
+                alloc.concat([
+                    alloc.reflow(r"The supported content encodings are "),
+                    alloc.keyword(r"br"),
+                    alloc.reflow(r", "),
+                    alloc.keyword(r"gzip"),
+                    alloc.reflow(r" and "),
+                    alloc.keyword(r"deflate"),
+                ]),
+                alloc.concat([
+                    alloc.tip(),
+                    alloc.reflow(r"Perhaps you can check if the URL is correctly formed, or if the server is correctly configured."),
+                ]),
+            ]);
+
+            Report {
+                filename: "UNKNOWN.roc".into(),
+                doc,
+                title: "UNSUPPORTED ENCODING".to_string(),
+                severity: Severity::Fatal,
+            }
+        }
+        Problem::MultipleEncodings(multiple_encodings) => {
+            let doc = alloc.stack([
+                alloc.reflow(r"I was trying to download this URL:"),
+                alloc.string((&url).to_string()).annotate(Annotation::Url).indent(4),
+                alloc.concat([
+                    alloc.reflow(r"But the server replied with multiple "),
+                    alloc.reflow(r"content encodings").annotate(Annotation::Emphasized),
+                    alloc.reflow(r": "),
+                    alloc.string(multiple_encodings).annotate(Annotation::Emphasized),
+                    alloc.reflow(r"."),
+                ]),
+                alloc.concat([
+                    alloc.reflow(r"The supported content encodings are "),
+                    alloc.keyword(r"br"),
+                    alloc.reflow(r", "),
+                    alloc.keyword(r"gzip"),
+                    alloc.reflow(r" and "),
+                    alloc.keyword(r"deflate"),
+                    alloc.reflow(r". However, the server reply can only contain "),
+                    alloc.reflow(r"one").annotate(Annotation::Emphasized),
+                    alloc.reflow(r"."),
+                ]),
+                alloc.concat([
+                    alloc.tip(),
+                    alloc.reflow(r"Perhaps you can check if the URL is correctly formed, or if the server is correctly configured."),
+                ]),
+            ]);
+
+            Report {
+                filename: "UNKNOWN.roc".into(),
+                doc,
+                title: "MULTIPLE ENCODINGS".to_string(),
+                severity: Severity::Fatal,
+            }
+        }
+        Problem::InvalidContentHash { expected, actual } => {
+            let doc = alloc.stack([
+                alloc.reflow(r"I was able to download this URL:"),
+                alloc.string((&url).to_string()).annotate(Annotation::Url).indent(4),
+                alloc.concat([
+                    alloc.reflow(r"I use a mechanism to detect if the file might "),
+                    alloc.reflow(r"have been tampered with. This could happen if "),
+                    alloc.reflow(r"the server or domain have been compromised."),
+                ]),
+                alloc.concat([
+                    alloc.reflow(r"This is the content signature I was "),
+                    alloc.reflow(r"expecting").annotate(Annotation::Emphasized),
+                    alloc.reflow(r":"),
+                ]),
+                alloc.string(expected).annotate(Annotation::PlainText).indent(4),
+                alloc.concat([
+                    alloc.reflow(r"However, this is the content signature I "),
+                    alloc.reflow(r"obtained").annotate(Annotation::Emphasized),
+                    alloc.reflow(r":"),
+                ]),
+                alloc.string(actual).annotate(Annotation::PlainText).indent(4),
+                alloc.reflow(r"To keep you secure, I will not execute this untrusted code."),
+                alloc.concat([
+                    alloc.tip(),
+                    alloc.reflow(r"Check if the URL is correctly formed and if this is the server you are expecting to connect to."),
+                ]),
+            ]);
+
+            Report {
+                filename: "UNKNOWN.roc".into(),
+                doc,
+                title: "INVALID CONTENT HASH".to_string(),
+                severity: Severity::Fatal,
+            }
+        }
+        // TODO: The reporting text for IoErr and FsExtraErr could probably be unified
+        Problem::IoErr(io_error) => {
+            let doc = alloc.stack([
+                alloc.reflow(r"I was trying to download this URL:"),
+                alloc
+                    .string((&url).to_string())
+                    .annotate(Annotation::Url)
+                    .indent(4),
+                alloc.reflow(r"But I encountered an IO (input/output) error:"),
+                alloc
+                    .string(io_error.to_string())
+                    .annotate(Annotation::PlainText)
+                    .indent(4),
+                // TODO: What should the tip for IO errors be?
+                // alloc.concat([
+                //     alloc.tip(),
+                //     alloc.reflow(r"Check the error message."),
+                // ]),
+            ]);
+
+            Report {
+                filename: "UNKNOWN.roc".into(),
+                doc,
+                title: "IO ERROR".to_string(),
+                severity: Severity::Fatal,
+            }
+        }
+        // TODO: The reporting text for IoErr and FsExtraErr could probably be unified
+        Problem::FsExtraErr(fs_extra_error) => {
+            let doc = alloc.stack([
+                alloc.reflow(r"I was trying to download this URL:"),
+                alloc
+                    .string((&url).to_string())
+                    .annotate(Annotation::Url)
+                    .indent(4),
+                alloc.reflow(r"But I encountered an IO (input/output) error:"),
+                alloc
+                    .string(fs_extra_error.to_string())
+                    .annotate(Annotation::PlainText)
+                    .indent(4),
+                // TODO: What should the tip for IO errors be?
+                // alloc.concat([
+                //     alloc.tip(),
+                //     alloc.reflow(r"Check the error message."),
+                // ]),
+            ]);
+
+            Report {
+                filename: "UNKNOWN.roc".into(),
+                doc,
+                title: "IO ERROR".to_string(),
+                severity: Severity::Fatal,
+            }
+        }
+        Problem::HttpErr(reqwest_error) => {
+            let doc = alloc.stack([
+                alloc.reflow(r"I was trying to download this URL:"),
+                alloc
+                    .string((&url).to_string())
+                    .annotate(Annotation::Url)
+                    .indent(4),
+                alloc.reflow(r"But I encountered a network error:"),
+                alloc
+                    .string(reqwest_error.to_string())
+                    .annotate(Annotation::PlainText)
+                    .indent(4),
+                // TODO: What should the tip for HTTP IO errors be?
+                // Should we import reqwest and check stuff like
+                // reqwest_error.{ is_redirect(), is_status(), is_timeout(), ... } ?
+                //
+                // alloc.concat([
+                //     alloc.tip(),
+                //     alloc.reflow(r"Check the error message."),
+                // ]),
+            ]);
+
+            Report {
+                filename: "UNKNOWN.roc".into(),
+                doc,
+                title: "HTTP ERROR".to_string(),
+                severity: Severity::Fatal,
+            }
+        }
+        Problem::InvalidUrl(roc_packaging::https::UrlProblem::InvalidExtensionSuffix(
+            invalid_suffix,
+        )) => {
+            let (suffix_text, annotation_style) = if invalid_suffix.is_empty() {
+                (r"empty".to_string(), Annotation::PlainText)
+            } else {
+                (invalid_suffix, Annotation::Emphasized)
+            };
+
+            let doc = alloc.stack([
+                alloc.reflow(r"I was trying to download this URL:"),
+                alloc
+                    .string((&url).to_string())
+                    .annotate(Annotation::Url)
+                    .indent(4),
+                alloc.concat([
+                    alloc.reflow(r"However, this file's extension ("),
+                    alloc.string(suffix_text).annotate(annotation_style),
+                    alloc.reflow(r") is not a supported extension."),
+                ]),
+                alloc.concat([
+                    alloc.reflow(r"The supported extensions are "),
+                    alloc.keyword(r".tar"),
+                    alloc.reflow(r", "),
+                    alloc.keyword(r".tar.gz"),
+                    alloc.reflow(r" and "),
+                    alloc.keyword(r".tar.br"),
+                ]),
+                alloc.concat([
+                    alloc.tip(),
+                    alloc.reflow(r"Check that you have the correct URL for this package/platform."),
+                ]),
+            ]);
+
+            Report {
+                filename: "UNKNOWN.roc".into(),
+                doc,
+                title: "INVALID EXTENSION SUFFIX".to_string(),
+                severity: Severity::Fatal,
+            }
+        }
+        Problem::InvalidUrl(roc_packaging::https::UrlProblem::MissingTarExt) => {
+            let doc = alloc.stack([
+                alloc.reflow(r"I was trying to download this URL:"),
+                alloc
+                    .string((&url).to_string())
+                    .annotate(Annotation::Url)
+                    .indent(4),
+                alloc.concat([
+                    alloc.reflow(r"However, this file's extension is not "),
+                    alloc.keyword(r".tar"),
+                    alloc.reflow(r"."),
+                ]),
+                alloc.concat([
+                    alloc.reflow(r"The supported extensions are "),
+                    alloc.keyword(r".tar"),
+                    alloc.reflow(r", "),
+                    alloc.keyword(r".tar.gz"),
+                    alloc.reflow(r" and "),
+                    alloc.keyword(r".tar.br"),
+                ]),
+                alloc.concat([
+                    alloc.tip(),
+                    alloc.reflow(r"Check that you have the correct URL for this package/platform."),
+                ]),
+            ]);
+
+            Report {
+                filename: "UNKNOWN.roc".into(),
+                doc,
+                title: "INVALID EXTENSION".to_string(),
+                severity: Severity::Fatal,
+            }
+        }
+        Problem::InvalidUrl(roc_packaging::https::UrlProblem::InvalidFragment(
+            invalid_fragment,
+        )) => {
+            let doc = alloc.stack([
+                alloc.reflow(r"I was trying to download this URL:"),
+                alloc
+                    .string((&url).to_string())
+                    .annotate(Annotation::Url)
+                    .indent(4),
+                alloc.concat([
+                    alloc.reflow(r"However, this URL's fragment (the part after #) "),
+                    alloc.reflow(r"is not valid. When present, the fragment must point to "),
+                    alloc.reflow(r"an existing "),
+                    alloc.keyword(r".roc"),
+                    alloc.reflow(r" file inside the package. Also, the filename can't be empty, "),
+                    alloc.reflow(r"so a fragment of #.roc would also not be valid. This is the "),
+                    alloc.reflow(r"invalid fragment I encountered: "),
+                ]),
+                alloc
+                    .string(invalid_fragment)
+                    .annotate(Annotation::Emphasized)
+                    .indent(4),
+                alloc.concat([
+                    alloc.tip(),
+                    alloc.reflow(r"Check that the fragment points to an existing "),
+                    alloc.keyword(r".roc"),
+                    alloc.reflow(r" file inside the package. You can download this package "),
+                    alloc.reflow(r"and inspect it locally."),
+                ]),
+            ]);
+
+            Report {
+                filename: "UNKNOWN.roc".into(),
+                doc,
+                title: "INVALID FRAGMENT".to_string(),
+                severity: Severity::Fatal,
+            }
+        }
+        Problem::InvalidUrl(roc_packaging::https::UrlProblem::MissingHash) => {
+            let doc = alloc.stack([
+                alloc.reflow(r"I was trying to download this URL:"),
+                alloc
+                    .string((&url).to_string())
+                    .annotate(Annotation::Url)
+                    .indent(4),
+                alloc.concat([
+                    alloc.reflow(r"I use a content hash to detect if the file might "),
+                    alloc.reflow(r"have been tampered with. This could happen if "),
+                    alloc.reflow(r"the server or domain have been compromised."),
+                ]),
+                alloc.concat([
+                    alloc.reflow(r"The way this works is that the name of the file "),
+                    alloc.reflow(r"is the BLAKE3 hash of the contents of the "),
+                    alloc.reflow(r"file itself. If someone would tamper with the file, "),
+                    alloc.reflow(r"I could notify and protect you. However, I could "),
+                    alloc.reflow(r"not find the expected hash on the URL above, "),
+                    alloc.reflow(r"so I cannot apply this tamper-check."),
+                ]),
+                alloc.concat([
+                    alloc.tip(),
+                    alloc
+                        .reflow(r"Check that you have the correct URL for this package/platform. "),
+                    alloc.reflow(r"Here is an example of how such a hash looks like: "),
+                    alloc
+                        .string(r"tE4xS_zLdmmxmHwHih9kHWQ7fsXtJr7W7h3425-eZFk".to_string())
+                        .annotate(Annotation::Emphasized),
+                ]),
+            ]);
+
+            Report {
+                filename: "UNKNOWN.roc".into(),
+                doc,
+                title: "MISSING PACKAGE HASH".to_string(),
+                severity: Severity::Fatal,
+            }
+        }
+        Problem::InvalidUrl(roc_packaging::https::UrlProblem::MissingHttps) => {
+            let doc = alloc.stack([
+                alloc.reflow(r"I was trying to download this URL:"),
+                alloc
+                    .string((&url).to_string())
+                    .annotate(Annotation::Url)
+                    .indent(4),
+                alloc.concat([
+                    alloc.reflow(r"For your security, I will only attempt to download "),
+                    alloc.reflow(r"files from servers which use the "),
+                    alloc.keyword(r"https"),
+                    alloc.reflow(r" protocol."),
+                ]),
+                alloc.concat([
+                    alloc.tip(),
+                    alloc.reflow(r"Check that you have the correct URL for this package/platform."),
+                ]),
+            ]);
+
+            Report {
+                filename: "UNKNOWN.roc".into(),
+                doc,
+                title: "HTTPS MANDATORY".to_string(),
+                severity: Severity::Fatal,
+            }
+        }
+        Problem::InvalidUrl(roc_packaging::https::UrlProblem::MisleadingCharacter) => {
+            let doc = alloc.stack([
+                alloc.reflow(r"I was trying to download this URL:"),
+                alloc
+                    .string((&url).to_string())
+                    .annotate(Annotation::Url)
+                    .indent(4),
+                alloc.concat([
+                    alloc.reflow(r"I have found one or more potentially misleading "),
+                    alloc.reflow(r"characters in this URL. Misleading characters are "),
+                    alloc.reflow(r"characters that look like others but aren't the same. "),
+                    alloc.reflow(r"The following characters are classified as misleading: "),
+                    alloc.keyword(r"@"),
+                    alloc.reflow(r", "),
+                    alloc.keyword("\u{2044}"),
+                    alloc.reflow(r" (unicode 2044), "),
+                    alloc.keyword("\u{2215}"),
+                    alloc.reflow(r" (unicode 2215), "),
+                    alloc.keyword("\u{FF0F}"),
+                    alloc.reflow(r" (unicode FF0F) and "),
+                    alloc.keyword("\u{29F8}"),
+                    alloc.reflow(r" (unicode 29F8). "),
+                ]),
+                alloc.concat([
+                    alloc.reflow(r"If you have a use-case for any of these characters we "),
+                    alloc.reflow(r"would like to hear about it. Reach out on "),
+                    alloc
+                        .string(r"https://github.com/roc-lang/roc/issues/5487".to_string())
+                        .annotate(Annotation::Url),
+                ]),
+                alloc.concat([
+                    alloc.tip(),
+                    alloc.reflow(r"Check that you have the correct URL for this package/platform."),
+                ]),
+            ]);
+
+            Report {
+                filename: "UNKNOWN.roc".into(),
+                doc,
+                title: "MISLEADING CHARACTERS".to_string(),
+                severity: Severity::Fatal,
+            }
+        }
+        Problem::DownloadTooBig(content_len) => {
+            let nice_bytes = Byte::from_bytes(content_len.into())
+                .get_appropriate_unit(false)
+                .format(3);
+            let doc = alloc.stack([
+                alloc.reflow(r"I was trying to download this URL:"),
+                alloc
+                    .string((&url).to_string())
+                    .annotate(Annotation::Url)
+                    .indent(4),
+                    alloc.concat([
+                        alloc.reflow(r"But the server stated this file is "),
+                        alloc.string(nice_bytes).annotate(Annotation::Keyword),
+                        alloc.reflow(r" in size. This is larger that the maximum size I can handle (around 32 GB)."),
+                    ]),
+                alloc.concat([
+                    alloc.tip(),
+                    alloc.reflow(r"Check that you have the correct URL for this package/platform. "),
+                    alloc.reflow(r"If you do, you should contact the package/platform's author and "),
+                    alloc.reflow(r"notify them about this issue."),
+                ]),
+            ]);
+
+            Report {
+                filename: "UNKNOWN.roc".into(),
+                doc,
+                title: "FILE TOO LARGE".to_string(),
+                severity: Severity::Fatal,
+            }
+        }
+    }
+}
+
 pub fn to_file_problem_report_string(filename: &Path, error: io::ErrorKind) -> String {
     let src_lines: Vec<&str> = Vec::new();
 

crates/reporting/tests/test_reporting.rs

@@ -10151,6 +10151,41 @@ In roc, functions are always written as a lambda, like{}
     "###
     );
 
+    test_report!(
+        forgot_to_remove_underscore,
+        indoc!(
+            r#"
+            \_foo -> foo
+            "#
+        ),
+        |golden| pretty_assertions::assert_eq!(
+            golden,
+            indoc!(
+                r###"── UNRECOGNIZED NAME ───────────────────────────────────── /code/proj/Main.roc ─
+
+                Nothing is named `foo` in this scope.
+
+                4│      \_foo -> foo
+                                 ^^^
+
+                There is an ignored identifier of a similar name here:
+
+                4│      \_foo -> foo
+                         ^^^^
+
+                Did you mean to remove the leading underscore?
+
+                If not, did you mean one of these?
+
+                    Box
+                    Bool
+                    U8
+                    F64
+                "###
+            ),
+        )
+    );
+
     test_report!(
         call_with_underscore_identifier,
         indoc!(
@@ -10162,17 +10197,102 @@ In roc, functions are always written as a lambda, like{}
         ),
         |golden| pretty_assertions::assert_eq!(
             golden,
-            &format!(
+            indoc!(
                 r###"── SYNTAX PROBLEM ──────────────────────────────────────── /code/proj/Main.roc ─
 
-Underscores are not allowed in identifier names:
+                An underscore is being used as a variable here:
 
-6│      f 1 _ 1
+                6│      f 1 _ 1
-{}
+                            ^
 
-I recommend using camelCase. It's the standard style in Roc code!
+                An underscore can be used to ignore a value when pattern matching, but
-"###,
+                it cannot be used as a variable.
-                "  " // TODO make the reporter not insert extraneous spaces here in the first place!
+                "###
+            ),
+        )
+    );
+
+    test_report!(
+        call_with_declared_identifier_starting_with_underscore,
+        indoc!(
+            r#"
+            f = \x, y, z -> x + y + z
+
+            \a, _b -> f a _b 1
+            "#
+        ),
+        |golden| pretty_assertions::assert_eq!(
+            golden,
+            indoc!(
+                r###"── SYNTAX PROBLEM ──────────────────────────────────────── /code/proj/Main.roc ─
+
+                This variable's name starts with an underscore:
+
+                6│      \a, _b -> f a _b 1
+                            ^^
+
+                But then it is used here:
+
+                6│      \a, _b -> f a _b 1
+                                      ^^
+
+                A variable's name can only start with an underscore if the variable is
+                unused. Since you are using this variable, you could remove the
+                underscore from its name in both places.
+                "###
+            ),
+        )
+    );
+
+    test_report!(
+        call_with_undeclared_identifier_starting_with_underscore,
+        indoc!(
+            r#"
+            f = \x, y, z -> x + y + z
+
+            \a, _b -> f a _r 1
+            "#
+        ),
+        |golden| pretty_assertions::assert_eq!(
+            golden,
+            indoc!(
+                r###"
+                ── SYNTAX PROBLEM ──────────────────────────────────────── /code/proj/Main.roc ─
+
+                This variable's name starts with an underscore:
+
+                6│      \a, _b -> f a _r 1
+                                      ^^
+
+                A variable's name can only start with an underscore if the variable is
+                unused. But it looks like the variable is being used here!
+                "###
+            ),
+        )
+    );
+
+    test_report!(
+        underscore_in_middle_of_identifier,
+        indoc!(
+            r#"
+            f = \x, y, z -> x + y + z
+
+            \a, _b -> f a var_name 1
+            "#
+        ),
+        |golden| pretty_assertions::assert_eq!(
+            golden,
+            indoc!(
+                r###"
+                ── SYNTAX PROBLEM ──────────────────────────────────────── /code/proj/Main.roc ─
+
+                Underscores are not allowed in identifier names:
+
+                6│      \a, _b -> f a var_name 1
+                                      ^^^^^^^^
+
+                I recommend using camelCase. It's the standard style in Roc code!
+                "###
             ),
         )
     );

crates/roc_std/src/lib.rs

@@ -36,7 +36,6 @@ extern "C" {
     ) -> *mut c_void;
     pub fn roc_dealloc(ptr: *mut c_void, alignment: u32);
     pub fn roc_panic(c_ptr: *mut c_void, tag_id: u32);
-    pub fn roc_memcpy(dst: *mut c_void, src: *mut c_void, n: usize) -> *mut c_void;
     pub fn roc_memset(dst: *mut c_void, c: i32, n: usize) -> *mut c_void;
 }
 

crates/roc_std/tests/test_roc_std.rs

@@ -45,12 +45,6 @@ pub unsafe extern "C" fn roc_panic(c_ptr: *mut c_void, tag_id: u32) {
     }
 }
 
-#[cfg(test)]
-#[no_mangle]
-pub unsafe extern "C" fn roc_memcpy(dst: *mut c_void, src: *mut c_void, n: usize) -> *mut c_void {
-    libc::memcpy(dst, src, n)
-}
-
 #[cfg(test)]
 #[no_mangle]
 pub unsafe extern "C" fn roc_memset(dst: *mut c_void, c: i32, n: usize) -> *mut c_void {

crates/valgrind/zig-platform/host.zig

@@ -67,10 +67,6 @@ export fn roc_panic(c_ptr: *anyopaque, tag_id: u32) callconv(.C) void {
     std.process.exit(0);
 }
 
-export fn roc_memcpy(dst: [*]u8, src: [*]u8, size: usize) callconv(.C) void {
-    return memcpy(dst, src, size);
-}
-
 export fn roc_memset(dst: [*]u8, value: i32, size: usize) callconv(.C) void {
     return memset(dst, value, size);
 }

examples/cli/cli-platform/src/lib.rs

@@ -9,7 +9,7 @@ use core::mem::MaybeUninit;
 use glue::Metadata;
 use roc_std::{RocDict, RocList, RocResult, RocStr};
 use std::borrow::{Borrow, Cow};
-use std::ffi::{ OsStr};
+use std::ffi::OsStr;
 use std::fs::File;
 use std::io::Write;
 use std::path::Path;
@@ -199,11 +199,6 @@ fn display_roc_fn(module_name: &str, fn_name: &str) -> String {
     format!("\u{001B}[36m{module_name}\u{001B}[39m.{fn_name}")
 }
 
-#[no_mangle]
-pub unsafe extern "C" fn roc_memcpy(dst: *mut c_void, src: *mut c_void, n: usize) -> *mut c_void {
-    libc::memcpy(dst, src, n)
-}
-
 #[no_mangle]
 pub unsafe extern "C" fn roc_memset(dst: *mut c_void, c: i32, n: usize) -> *mut c_void {
     libc::memset(dst, c, n)

examples/cli/effects-platform/host.zig

@@ -81,10 +81,6 @@ export fn roc_panic(c_ptr: *anyopaque, tag_id: u32) callconv(.C) void {
     std.process.exit(0);
 }
 
-export fn roc_memcpy(dst: [*]u8, src: [*]u8, size: usize) callconv(.C) void {
-    return memcpy(dst, src, size);
-}
-
 export fn roc_memset(dst: [*]u8, value: i32, size: usize) callconv(.C) void {
     return memset(dst, value, size);
 }

examples/cli/false-interpreter/platform/src/lib.rs

@@ -61,11 +61,6 @@ pub unsafe extern "C" fn roc_panic(c_ptr: *mut c_void, tag_id: u32) {
     }
 }
 
-#[no_mangle]
-pub unsafe extern "C" fn roc_memcpy(dst: *mut c_void, src: *mut c_void, n: usize) -> *mut c_void {
-    libc::memcpy(dst, src, n)
-}
-
 #[no_mangle]
 pub unsafe extern "C" fn roc_memset(dst: *mut c_void, c: i32, n: usize) -> *mut c_void {
     libc::memset(dst, c, n)

examples/cli/tui-platform/host.zig

@@ -136,10 +136,6 @@ export fn roc_panic(c_ptr: *anyopaque, tag_id: u32) callconv(.C) void {
     std.process.exit(0);
 }
 
-export fn roc_memcpy(dst: [*]u8, src: [*]u8, size: usize) callconv(.C) void {
-    return memcpy(dst, src, size);
-}
-
 export fn roc_memset(dst: [*]u8, value: i32, size: usize) callconv(.C) void {
     return memset(dst, value, size);
 }

examples/glue/rust-platform/src/lib.rs

@@ -44,11 +44,6 @@ pub unsafe extern "C" fn roc_panic(c_ptr: *mut c_void, tag_id: u32) {
     }
 }
 
-#[no_mangle]
-pub unsafe extern "C" fn roc_memcpy(dst: *mut c_void, src: *mut c_void, n: usize) -> *mut c_void {
-    libc::memcpy(dst, src, n)
-}
-
 #[no_mangle]
 pub unsafe extern "C" fn roc_memset(dst: *mut c_void, c: i32, n: usize) -> *mut c_void {
     libc::memset(dst, c, n)

examples/gui/breakout/platform/src/roc.rs

@@ -196,11 +196,6 @@ pub unsafe extern "C" fn roc_panic(c_ptr: *mut c_void, tag_id: u32) {
     }
 }
 
-#[no_mangle]
-pub unsafe extern "C" fn roc_memcpy(dst: *mut c_void, src: *mut c_void, n: usize) -> *mut c_void {
-    libc::memcpy(dst, src, n)
-}
-
 #[no_mangle]
 pub unsafe extern "C" fn roc_memset(dst: *mut c_void, c: i32, n: usize) -> *mut c_void {
     libc::memset(dst, c, n)

examples/gui/platform/src/roc.rs

@@ -38,11 +38,6 @@ pub unsafe extern "C" fn roc_panic(c_ptr: *mut c_void, tag_id: u32) {
     }
 }
 
-#[no_mangle]
-pub unsafe extern "C" fn roc_memcpy(dst: *mut c_void, src: *mut c_void, n: usize) -> *mut c_void {
-    libc::memcpy(dst, src, n)
-}
-
 #[no_mangle]
 pub unsafe extern "C" fn roc_memset(dst: *mut c_void, c: i32, n: usize) -> *mut c_void {
     libc::memset(dst, c, n)

examples/jvm-interop/bridge.c

@@ -42,11 +42,6 @@ void roc_dealloc(void *ptr, unsigned int alignment)
     free(ptr);
 }
 
-void *roc_memcpy(void *dest, const void *src, size_t n)
-{
-    return memcpy(dest, src, n);
-}
-
 void *roc_memset(void *str, int c, size_t n)
 {
     return memset(str, c, n);

examples/nodejs-interop/native-c-api/demo.c

@@ -27,11 +27,6 @@ void roc_panic(void *ptr, unsigned int alignment)
     napi_throw_error(napi_global_env, NULL, (char *)ptr);
 }
 
-void *roc_memcpy(void *dest, const void *src, size_t n)
-{
-    return memcpy(dest, src, n);
-}
-
 void *roc_memset(void *str, int c, size_t n) { return memset(str, c, n); }
 
 // Reference counting

examples/nodejs-interop/wasm/platform/host.zig

@@ -33,10 +33,6 @@ export fn roc_dealloc(c_ptr: *anyopaque, alignment: u32) callconv(.C) void {
     free(@alignCast(@alignOf(Align), @ptrCast([*]u8, c_ptr)));
 }
 
-export fn roc_memcpy(dest: *anyopaque, src: *anyopaque, count: usize) callconv(.C) void {
-    _ = memcpy(dest, src, count);
-}
-
 // NOTE roc_panic is provided in the JS file, so it can throw an exception
 
 extern fn roc__mainForHost_1_exposed(*RocStr) void;

examples/platform-switching/c-platform/host.c

@@ -30,10 +30,6 @@ void roc_panic(void* ptr, unsigned int alignment) {
   exit(0);
 }
 
-void* roc_memcpy(void* dest, const void* src, size_t n) {
-  return memcpy(dest, src, n);
-}
-
 void* roc_memset(void* str, int c, size_t n) { return memset(str, c, n); }
 
 int roc_shm_open(char* name, int oflag, int mode) {

examples/platform-switching/rust-platform/src/lib.rs

@@ -44,11 +44,6 @@ pub unsafe extern "C" fn roc_panic(c_ptr: *mut c_void, tag_id: u32) {
     }
 }
 
-#[no_mangle]
-pub unsafe extern "C" fn roc_memcpy(dst: *mut c_void, src: *mut c_void, n: usize) -> *mut c_void {
-    libc::memcpy(dst, src, n)
-}
-
 #[no_mangle]
 pub unsafe extern "C" fn roc_memset(dst: *mut c_void, c: i32, n: usize) -> *mut c_void {
     libc::memset(dst, c, n)

examples/platform-switching/web-assembly-platform/host.zig

@@ -33,10 +33,6 @@ export fn roc_dealloc(c_ptr: *anyopaque, alignment: u32) callconv(.C) void {
     free(@alignCast(@alignOf(Align), @ptrCast([*]u8, c_ptr)));
 }
 
-export fn roc_memcpy(dest: *anyopaque, src: *anyopaque, count: usize) callconv(.C) void {
-    _ = memcpy(dest, src, count);
-}
-
 // NOTE roc_panic is provided in the JS file, so it can throw an exception
 
 extern fn roc__mainForHost_1_exposed(*RocStr) void;

examples/platform-switching/zig-platform/host.zig

@@ -67,10 +67,6 @@ export fn roc_panic(c_ptr: *anyopaque, tag_id: u32) callconv(.C) void {
     std.process.exit(0);
 }
 
-export fn roc_memcpy(dst: [*]u8, src: [*]u8, size: usize) callconv(.C) void {
-    return memcpy(dst, src, size);
-}
-
 export fn roc_memset(dst: [*]u8, value: i32, size: usize) callconv(.C) void {
     return memset(dst, value, size);
 }

examples/python-interop/demo.c

@@ -27,11 +27,6 @@ __attribute__((noreturn)) void roc_panic(void *ptr, unsigned int alignment)
     PyErr_SetString(PyExc_RuntimeError, (char *)ptr);
 }
 
-void *roc_memcpy(void *dest, const void *src, size_t n)
-{
-    return memcpy(dest, src, n);
-}
-
 void *roc_memset(void *str, int c, size_t n) { return memset(str, c, n); }
 
 // Reference counting

examples/python-interop/platform/host.c

@@ -24,10 +24,6 @@ void roc_panic(void* ptr, unsigned int alignment) {
   exit(0);
 }
 
-void* roc_memcpy(void* dest, const void* src, size_t n) {
-  return memcpy(dest, src, n);
-}
-
 void* roc_memset(void* str, int c, size_t n) { return memset(str, c, n); }
 
 int roc_shm_open(char* name, int oflag, int mode) {

examples/ruby-interop/demo.c

@@ -23,11 +23,6 @@ __attribute__((noreturn)) void roc_panic(void *ptr, unsigned int alignment)
     rb_raise(rb_eException, "%s", (char *)ptr);
 }
 
-void *roc_memcpy(void *dest, const void *src, size_t n)
-{
-    return memcpy(dest, src, n);
-}
-
 void *roc_memset(void *str, int c, size_t n) { return memset(str, c, n); }
 
 // Reference counting

examples/ruby-interop/platform/host.c

@@ -24,10 +24,6 @@ void roc_panic(void* ptr, unsigned int alignment) {
   exit(0);
 }
 
-void* roc_memcpy(void* dest, const void* src, size_t n) {
-  return memcpy(dest, src, n);
-}
-
 void* roc_memmove(void* dest, const void* src, size_t n){
   return memmove(dest, src, n);
 }

examples/static-site-gen/platform/src/lib.rs

@@ -9,10 +9,10 @@ use std::os::raw::c_char;
 use std::path::{Path, PathBuf};
 
 use syntect::easy::HighlightLines;
+use syntect::highlighting::{Style, ThemeSet};
+use syntect::html::{ClassStyle, ClassedHTMLGenerator};
 use syntect::parsing::SyntaxSet;
-use syntect::highlighting::{ThemeSet, Style};
+use syntect::util::LinesWithEndings;
-use syntect::util::{LinesWithEndings};
-use syntect::html::{ClassedHTMLGenerator, ClassStyle};
 
 extern "C" {
     #[link_name = "roc__transformFileContentForHost_1_exposed"]
@@ -98,15 +98,6 @@ pub unsafe extern "C" fn roc_panic(c_ptr: *mut c_void, tag_id: u32) {
     }
 }
 
-#[no_mangle]
-pub unsafe extern "C" fn roc_memcpy(
-    dest: *mut c_void,
-    src: *const c_void,
-    bytes: usize,
-) -> *mut c_void {
-    libc::memcpy(dest, src, bytes)
-}
-
 #[no_mangle]
 pub unsafe extern "C" fn roc_memset(dst: *mut c_void, c: i32, n: usize) -> *mut c_void {
     libc::memset(dst, c, n)
@@ -216,9 +207,9 @@ fn process_file(input_dir: &Path, output_dir: &Path, input_file: &Path) -> Resul
     // And track a little bit of state
     let mut in_code_block = false;
     let mut is_roc_code = false;
-    let syntax_set : syntect::parsing::SyntaxSet = SyntaxSet::load_defaults_newlines();
+    let syntax_set: syntect::parsing::SyntaxSet = SyntaxSet::load_defaults_newlines();
-    let theme_set : syntect::highlighting::ThemeSet = ThemeSet::load_defaults();
+    let theme_set: syntect::highlighting::ThemeSet = ThemeSet::load_defaults();
-    
+
     for event in parser {
         match event {
             pulldown_cmark::Event::Code(code_str) => {
@@ -227,23 +218,25 @@ fn process_file(input_dir: &Path, output_dir: &Path, input_file: &Path) -> Resul
                         .strip_prefix("roc!")
                         .expect("expected leading 'roc!'");
 
-                    let highlighted_html = roc_highlight::highlight_roc_code_inline(stripped.to_string().as_str());
+                    let highlighted_html =
-                    
+                        roc_highlight::highlight_roc_code_inline(stripped.to_string().as_str());
+
                     parser_with_highlighting.push(pulldown_cmark::Event::Html(
                         pulldown_cmark::CowStr::from(highlighted_html),
                     ));
                 } else {
-                    let inline_code = pulldown_cmark::CowStr::from(format!("<code>{}</code>", code_str));
+                    let inline_code =
-                    parser_with_highlighting.push(
+                        pulldown_cmark::CowStr::from(format!("<code>{}</code>", code_str));
-                        pulldown_cmark::Event::Html(inline_code)
+                    parser_with_highlighting.push(pulldown_cmark::Event::Html(inline_code));
-                    );
                 }
             }
             pulldown_cmark::Event::Start(pulldown_cmark::Tag::CodeBlock(cbk)) => {
                 in_code_block = true;
                 is_roc_code = is_roc_code_block(&cbk);
             }
-            pulldown_cmark::Event::End(pulldown_cmark::Tag::CodeBlock(pulldown_cmark::CodeBlockKind::Fenced(extention_str))) => {
+            pulldown_cmark::Event::End(pulldown_cmark::Tag::CodeBlock(
+                pulldown_cmark::CodeBlockKind::Fenced(extention_str),
+            )) => {
                 if in_code_block {
                     match replace_code_with_static_file(&code_to_highlight, input_file) {
                         None => {}
@@ -263,13 +256,19 @@ fn process_file(input_dir: &Path, output_dir: &Path, input_file: &Path) -> Resul
                     if is_roc_code {
                         highlighted_html = roc_highlight::highlight_roc_code(&code_to_highlight)
                     } else if let Some(syntax) = syntax_set.find_syntax_by_token(&extention_str) {
-                        let mut h = HighlightLines::new(syntax, &theme_set.themes["base16-ocean.dark"]);
+                        let mut h =
+                            HighlightLines::new(syntax, &theme_set.themes["base16-ocean.dark"]);
 
-                        let mut html_generator = ClassedHTMLGenerator::new_with_class_style(syntax, &syntax_set, ClassStyle::Spaced);
+                        let mut html_generator = ClassedHTMLGenerator::new_with_class_style(
+                            syntax,
+                            &syntax_set,
+                            ClassStyle::Spaced,
+                        );
                         for line in LinesWithEndings::from(&code_to_highlight) {
                             html_generator.parse_html_for_line_which_includes_newline(line);
                         }
-                        highlighted_html = format!("<pre><samp>{}</pre></samp>", html_generator.finalize())
+                        highlighted_html =
+                            format!("<pre><samp>{}</pre></samp>", html_generator.finalize())
                     } else {
                         highlighted_html = format!("<pre><samp>{}</pre></samp>", &code_to_highlight)
                     }
@@ -362,12 +361,11 @@ fn is_roc_code_block(cbk: &pulldown_cmark::CodeBlockKind) -> bool {
 fn replace_code_with_static_file(code: &str, input_file: &Path) -> Option<String> {
     let input_dir = input_file.parent()?;
     let trimmed_code = code.trim();
-    
+
     // Confirm the code block starts with a `file:` tag
     match trimmed_code.strip_prefix("file:") {
         None => None,
         Some(path) => {
-
             // File must be located in input folder or sub-directory
             if path.contains("../") {
                 panic!("ERROR File must be located within the input diretory!");
@@ -378,7 +376,10 @@ fn replace_code_with_static_file(code: &str, input_file: &Path) -> Option<String
             // Check file exists before opening
             match file_path.try_exists() {
                 Err(_) | Ok(false) => {
-                    panic!("ERROR File does not exist: \"{}\"", file_path.to_str().unwrap());
+                    panic!(
+                        "ERROR File does not exist: \"{}\"",
+                        file_path.to_str().unwrap()
+                    );
                 }
                 Ok(true) => {
                     let vec_u8 = fs::read(file_path).ok()?;
@@ -388,4 +389,4 @@ fn replace_code_with_static_file(code: &str, input_file: &Path) -> Option<String
             }
         }
     }
-}
+}

examples/virtual-dom-wip/platform/src/client-side/host.zig

@@ -28,10 +28,6 @@ export fn roc_dealloc(c_ptr: *anyopaque, alignment: u32) callconv(.C) void {
     free(@alignCast(@alignOf(Align), @ptrCast([*]u8, c_ptr)));
 }
 
-export fn roc_memcpy(dest: *anyopaque, src: *anyopaque, count: usize) callconv(.C) void {
-    _ = memcpy(dest, src, count);
-}
-
 export fn roc_panic(message: RocStr, tag_id: u32) callconv(.C) void {
     _ = tag_id;
     const msg = @ptrCast([*:0]const u8, c_ptr);

examples/virtual-dom-wip/platform/src/server-side/host.zig

@@ -28,10 +28,6 @@ export fn roc_dealloc(c_ptr: *anyopaque, alignment: u32) callconv(.C) void {
     free(@alignCast(@alignOf(Align), @ptrCast([*]u8, c_ptr)));
 }
 
-export fn roc_memcpy(dest: *anyopaque, src: *anyopaque, count: usize) callconv(.C) void {
-    _ = memcpy(dest, src, count);
-}
-
 export fn roc_panic(c_ptr: *anyopaque, tag_id: u32) callconv(.C) void {
     _ = tag_id;
     const msg = @ptrCast([*:0]const u8, c_ptr);

typos.toml

@@ -1,3 +1,3 @@
 [files]
-extend-exclude = ["crates/vendor/", "examples/static-site-gen/input/"]
+extend-exclude = ["crates/vendor/", "examples/static-site-gen/input/", "COPYRIGHT"]