Merge branch 'trunk' into gen-equality

Cargo.lock

@@ -816,6 +816,7 @@ dependencies = [
  "pretty_assertions",
  "pulldown-cmark",
  "roc_builtins",
+ "roc_can",
  "roc_collections",
  "roc_load",
  "serde",

cli/src/build.rs

@@ -3,6 +3,7 @@ use roc_build::{
     link::{link, rebuild_host, LinkType},
     program,
 };
+use roc_can::builtins::builtin_defs_map;
 use roc_collections::all::MutMap;
 use roc_gen::llvm::build::OptLevel;
 use roc_load::file::LoadingProblem;
@@ -47,6 +48,7 @@ pub fn build_file<'a>(
         src_dir.as_path(),
         subs_by_module,
         ptr_bytes,
+        builtin_defs_map,
     )?;
 
     let path_to_platform = loaded.platform_path.clone();

cli/src/repl/gen.rs

@@ -3,6 +3,7 @@ use bumpalo::Bump;
 use inkwell::context::Context;
 use roc_build::link::module_to_dylib;
 use roc_build::program::FunctionIterator;
+use roc_can::builtins::builtin_defs_map;
 use roc_collections::all::{MutMap, MutSet};
 use roc_fmt::annotation::Formattable;
 use roc_fmt::annotation::{Newlines, Parens};
@@ -51,6 +52,7 @@ pub fn gen_and_eval<'a>(
         src_dir,
         exposed_types,
         ptr_bytes,
+        builtin_defs_map,
     );
 
     let mut loaded = match loaded {
@@ -125,6 +127,9 @@ pub fn gen_and_eval<'a>(
         Ok(ReplOutput::Problems(lines))
     } else {
         let context = Context::create();
+
+        let ptr_bytes = target.pointer_width().unwrap().bytes() as u32;
+
         let module = arena.alloc(roc_gen::llvm::build::module_from_builtins(&context, ""));
         let builder = context.create_builder();
 
@@ -157,8 +162,6 @@ pub fn gen_and_eval<'a>(
             }
         };
 
-        let ptr_bytes = target.pointer_width().unwrap().bytes() as u32;
-
         let module = arena.alloc(module);
         let (module_pass, function_pass) =
             roc_gen::llvm::build::construct_optimization_passes(module, opt_level);

compiler/build/src/program.rs

@@ -74,7 +74,6 @@ pub fn gen_from_mono_module(
     }
 
     // Generate the binary
-
     let context = Context::create();
     let module = arena.alloc(module_from_builtins(&context, "app"));
 
@@ -94,9 +93,8 @@ pub fn gen_from_mono_module(
     let (dibuilder, compile_unit) = roc_gen::llvm::build::Env::new_debug_info(module);
     let (mpm, fpm) = roc_gen::llvm::build::construct_optimization_passes(module, opt_level);
 
-    let ptr_bytes = target.pointer_width().unwrap().bytes() as u32;
-
     // Compile and add all the Procs before adding main
+    let ptr_bytes = target.pointer_width().unwrap().bytes() as u32;
     let env = roc_gen::llvm::build::Env {
         arena: &arena,
         builder: &builder,

compiler/builtins/bitcode/src/dict.zig

@@ -0,0 +1,139 @@
+const std = @import("std");
+const testing = std.testing;
+const expectEqual = testing.expectEqual;
+const mem = std.mem;
+const Allocator = mem.Allocator;
+
+const level_size = 32;
+
+const InPlace = packed enum(u8) {
+    InPlace,
+    Clone,
+};
+
+const Slot = packed enum(u8) {
+    Empty,
+    Filled,
+    PreviouslyFilled,
+};
+
+pub const RocDict = extern struct {
+    dict_bytes: ?[*]u8,
+    dict_slot_len: usize,
+    dict_entries_len: usize,
+
+    pub fn empty() RocDict {
+        return RocDict{
+            .dict_entries_len = 0,
+            .dict_slot_len = 0,
+            .dict_bytes = null,
+        };
+    }
+
+    pub fn init(allocator: *Allocator, bytes_ptr: [*]const u8, number_of_slots: usize, number_of_entries: usize, key_size: usize, value_size: usize) RocDict {
+        var result = RocDict.allocate(
+            allocator,
+            InPlace.Clone,
+            number_of_slots,
+            number_of_entries,
+            key_size,
+            value_size,
+        );
+
+        @memcpy(result.asU8ptr(), bytes_ptr, number_of_slots);
+
+        return result;
+    }
+
+    pub fn deinit(self: RocDict, allocator: *Allocator, key_size: usize, value_size: usize) void {
+        if (!self.isEmpty()) {
+            const slot_size = slotSize(key_size, value_size);
+
+            const dict_bytes_ptr: [*]u8 = self.dict_bytes orelse unreachable;
+
+            const dict_bytes: []u8 = dict_bytes_ptr[0..(self.dict_slot_len)];
+            allocator.free(dict_bytes);
+        }
+    }
+
+    pub fn allocate(
+        allocator: *Allocator,
+        result_in_place: InPlace,
+        number_of_slots: usize,
+        number_of_entries: usize,
+        key_size: usize,
+        value_size: usize,
+    ) RocDict {
+        const slot_size = slotSize(key_size, value_size);
+
+        const length = @sizeOf(usize) + (number_of_slots * slot_size);
+
+        var new_bytes: []usize = allocator.alloc(usize, length) catch unreachable;
+
+        if (result_in_place == InPlace.InPlace) {
+            new_bytes[0] = @intCast(usize, number_of_slots);
+        } else {
+            const v: isize = std.math.minInt(isize);
+            new_bytes[0] = @bitCast(usize, v);
+        }
+
+        var first_slot = @ptrCast([*]align(@alignOf(usize)) u8, new_bytes);
+        first_slot += @sizeOf(usize);
+
+        return RocDict{
+            .dict_bytes = first_slot,
+            .dict_slot_len = number_of_slots,
+            .dict_entries_len = number_of_entries,
+        };
+    }
+
+    pub fn asU8ptr(self: RocDict) [*]u8 {
+        return @ptrCast([*]u8, self.dict_bytes);
+    }
+
+    pub fn contains(self: RocDict, key_size: usize, key_ptr: *const c_void, hash_code: u64) bool {
+        return false;
+    }
+
+    pub fn len(self: RocDict) usize {
+        return self.dict_entries_len;
+    }
+
+    pub fn isEmpty(self: RocDict) bool {
+        return self.len() == 0;
+    }
+
+    pub fn clone(self: RocDict, allocator: *Allocator, in_place: InPlace, key_size: usize, value_size: usize) RocDict {
+        var new_dict = RocDict.init(allocator, self.dict_slot_len, self.dict_entries_len, key_size, value_size);
+
+        var old_bytes: [*]u8 = @ptrCast([*]u8, self.dict_bytes);
+        var new_bytes: [*]u8 = @ptrCast([*]u8, new_dict.dict_bytes);
+
+        @memcpy(new_bytes, old_bytes, self.dict_slot_len);
+
+        return new_dict;
+    }
+};
+
+// Dict.empty
+pub fn dictEmpty() callconv(.C) RocDict {
+    return RocDict.empty();
+}
+
+pub fn slotSize(key_size: usize, value_size: usize) usize {
+    return @sizeOf(Slot) + key_size + value_size;
+}
+
+// Dict.len
+pub fn dictLen(dict: RocDict) callconv(.C) usize {
+    return dict.dict_entries_len;
+}
+
+test "RocDict.init() contains nothing" {
+    const key_size = @sizeOf(usize);
+    const value_size = @sizeOf(usize);
+
+    const dict = dictEmpty();
+
+    expectEqual(false, dict.contains(4, @ptrCast(*const c_void, &""), 9));
+}

compiler/builtins/bitcode/src/hash.zig

@@ -0,0 +1,255 @@
+// SPDX-License-Identifier: MIT
+// Copyright (c) 2015-2021 Zig Contributors
+// This file is part of [zig](https://ziglang.org/), which is MIT licensed.
+// The MIT license requires this copyright notice to be included in all copies
+// and substantial portions of the software.
+const std = @import("std");
+const str = @import("str.zig");
+const mem = std.mem;
+
+pub fn wyhash(seed: u64, bytes: ?[*]const u8, length: usize) callconv(.C) u64 {
+    const stdout = std.io.getStdOut().writer();
+
+    if (bytes) |nonnull| {
+        return wyhash_hash(seed, nonnull[0..length]);
+    } else {
+        return 42;
+    }
+}
+
+pub fn wyhash_rocstr(seed: u64, input: str.RocStr) callconv(.C) u64 {
+    return wyhash_hash(seed, input.asSlice());
+}
+
+const primes = [_]u64{
+    0xa0761d6478bd642f,
+    0xe7037ed1a0b428db,
+    0x8ebc6af09c88c6e3,
+    0x589965cc75374cc3,
+    0x1d8e4e27c47d124f,
+};
+
+fn read_bytes(comptime bytes: u8, data: []const u8) u64 {
+    const T = std.meta.Int(.unsigned, 8 * bytes);
+    return mem.readIntLittle(T, data[0..bytes]);
+}
+
+fn read_8bytes_swapped(data: []const u8) u64 {
+    return (read_bytes(4, data) << 32 | read_bytes(4, data[4..]));
+}
+
+fn mum(a: u64, b: u64) u64 {
+    var r = std.math.mulWide(u64, a, b);
+    r = (r >> 64) ^ r;
+    return @truncate(u64, r);
+}
+
+fn mix0(a: u64, b: u64, seed: u64) u64 {
+    return mum(a ^ seed ^ primes[0], b ^ seed ^ primes[1]);
+}
+
+fn mix1(a: u64, b: u64, seed: u64) u64 {
+    return mum(a ^ seed ^ primes[2], b ^ seed ^ primes[3]);
+}
+
+// Wyhash version which does not store internal state for handling partial buffers.
+// This is needed so that we can maximize the speed for the short key case, which will
+// use the non-iterative api which the public Wyhash exposes.
+const WyhashStateless = struct {
+    seed: u64,
+    msg_len: usize,
+
+    pub fn init(seed: u64) WyhashStateless {
+        return WyhashStateless{
+            .seed = seed,
+            .msg_len = 0,
+        };
+    }
+
+    fn round(self: *WyhashStateless, b: []const u8) void {
+        std.debug.assert(b.len == 32);
+
+        self.seed = mix0(
+            read_bytes(8, b[0..]),
+            read_bytes(8, b[8..]),
+            self.seed,
+        ) ^ mix1(
+            read_bytes(8, b[16..]),
+            read_bytes(8, b[24..]),
+            self.seed,
+        );
+    }
+
+    pub fn update(self: *WyhashStateless, b: []const u8) void {
+        std.debug.assert(b.len % 32 == 0);
+
+        var off: usize = 0;
+        while (off < b.len) : (off += 32) {
+            @call(.{ .modifier = .always_inline }, self.round, .{b[off .. off + 32]});
+        }
+
+        self.msg_len += b.len;
+    }
+
+    pub fn final(self: *WyhashStateless, b: []const u8) u64 {
+        std.debug.assert(b.len < 32);
+
+        const seed = self.seed;
+        const rem_len = @intCast(u5, b.len);
+        const rem_key = b[0..rem_len];
+
+        self.seed = switch (rem_len) {
+            0 => seed,
+            1 => mix0(read_bytes(1, rem_key), primes[4], seed),
+            2 => mix0(read_bytes(2, rem_key), primes[4], seed),
+            3 => mix0((read_bytes(2, rem_key) << 8) | read_bytes(1, rem_key[2..]), primes[4], seed),
+            4 => mix0(read_bytes(4, rem_key), primes[4], seed),
+            5 => mix0((read_bytes(4, rem_key) << 8) | read_bytes(1, rem_key[4..]), primes[4], seed),
+            6 => mix0((read_bytes(4, rem_key) << 16) | read_bytes(2, rem_key[4..]), primes[4], seed),
+            7 => mix0((read_bytes(4, rem_key) << 24) | (read_bytes(2, rem_key[4..]) << 8) | read_bytes(1, rem_key[6..]), primes[4], seed),
+            8 => mix0(read_8bytes_swapped(rem_key), primes[4], seed),
+            9 => mix0(read_8bytes_swapped(rem_key), read_bytes(1, rem_key[8..]), seed),
+            10 => mix0(read_8bytes_swapped(rem_key), read_bytes(2, rem_key[8..]), seed),
+            11 => mix0(read_8bytes_swapped(rem_key), (read_bytes(2, rem_key[8..]) << 8) | read_bytes(1, rem_key[10..]), seed),
+            12 => mix0(read_8bytes_swapped(rem_key), read_bytes(4, rem_key[8..]), seed),
+            13 => mix0(read_8bytes_swapped(rem_key), (read_bytes(4, rem_key[8..]) << 8) | read_bytes(1, rem_key[12..]), seed),
+            14 => mix0(read_8bytes_swapped(rem_key), (read_bytes(4, rem_key[8..]) << 16) | read_bytes(2, rem_key[12..]), seed),
+            15 => mix0(read_8bytes_swapped(rem_key), (read_bytes(4, rem_key[8..]) << 24) | (read_bytes(2, rem_key[12..]) << 8) | read_bytes(1, rem_key[14..]), seed),
+            16 => mix0(read_8bytes_swapped(rem_key), read_8bytes_swapped(rem_key[8..]), seed),
+            17 => mix0(read_8bytes_swapped(rem_key), read_8bytes_swapped(rem_key[8..]), seed) ^ mix1(read_bytes(1, rem_key[16..]), primes[4], seed),
+            18 => mix0(read_8bytes_swapped(rem_key), read_8bytes_swapped(rem_key[8..]), seed) ^ mix1(read_bytes(2, rem_key[16..]), primes[4], seed),
+            19 => mix0(read_8bytes_swapped(rem_key), read_8bytes_swapped(rem_key[8..]), seed) ^ mix1((read_bytes(2, rem_key[16..]) << 8) | read_bytes(1, rem_key[18..]), primes[4], seed),
+            20 => mix0(read_8bytes_swapped(rem_key), read_8bytes_swapped(rem_key[8..]), seed) ^ mix1(read_bytes(4, rem_key[16..]), primes[4], seed),
+            21 => mix0(read_8bytes_swapped(rem_key), read_8bytes_swapped(rem_key[8..]), seed) ^ mix1((read_bytes(4, rem_key[16..]) << 8) | read_bytes(1, rem_key[20..]), primes[4], seed),
+            22 => mix0(read_8bytes_swapped(rem_key), read_8bytes_swapped(rem_key[8..]), seed) ^ mix1((read_bytes(4, rem_key[16..]) << 16) | read_bytes(2, rem_key[20..]), primes[4], seed),
+            23 => mix0(read_8bytes_swapped(rem_key), read_8bytes_swapped(rem_key[8..]), seed) ^ mix1((read_bytes(4, rem_key[16..]) << 24) | (read_bytes(2, rem_key[20..]) << 8) | read_bytes(1, rem_key[22..]), primes[4], seed),
+            24 => mix0(read_8bytes_swapped(rem_key), read_8bytes_swapped(rem_key[8..]), seed) ^ mix1(read_8bytes_swapped(rem_key[16..]), primes[4], seed),
+            25 => mix0(read_8bytes_swapped(rem_key), read_8bytes_swapped(rem_key[8..]), seed) ^ mix1(read_8bytes_swapped(rem_key[16..]), read_bytes(1, rem_key[24..]), seed),
+            26 => mix0(read_8bytes_swapped(rem_key), read_8bytes_swapped(rem_key[8..]), seed) ^ mix1(read_8bytes_swapped(rem_key[16..]), read_bytes(2, rem_key[24..]), seed),
+            27 => mix0(read_8bytes_swapped(rem_key), read_8bytes_swapped(rem_key[8..]), seed) ^ mix1(read_8bytes_swapped(rem_key[16..]), (read_bytes(2, rem_key[24..]) << 8) | read_bytes(1, rem_key[26..]), seed),
+            28 => mix0(read_8bytes_swapped(rem_key), read_8bytes_swapped(rem_key[8..]), seed) ^ mix1(read_8bytes_swapped(rem_key[16..]), read_bytes(4, rem_key[24..]), seed),
+            29 => mix0(read_8bytes_swapped(rem_key), read_8bytes_swapped(rem_key[8..]), seed) ^ mix1(read_8bytes_swapped(rem_key[16..]), (read_bytes(4, rem_key[24..]) << 8) | read_bytes(1, rem_key[28..]), seed),
+            30 => mix0(read_8bytes_swapped(rem_key), read_8bytes_swapped(rem_key[8..]), seed) ^ mix1(read_8bytes_swapped(rem_key[16..]), (read_bytes(4, rem_key[24..]) << 16) | read_bytes(2, rem_key[28..]), seed),
+            31 => mix0(read_8bytes_swapped(rem_key), read_8bytes_swapped(rem_key[8..]), seed) ^ mix1(read_8bytes_swapped(rem_key[16..]), (read_bytes(4, rem_key[24..]) << 24) | (read_bytes(2, rem_key[28..]) << 8) | read_bytes(1, rem_key[30..]), seed),
+        };
+
+        self.msg_len += b.len;
+        return mum(self.seed ^ self.msg_len, primes[4]);
+    }
+
+    pub fn hash(seed: u64, input: []const u8) u64 {
+        const aligned_len = input.len - (input.len % 32);
+
+        var c = WyhashStateless.init(seed);
+        @call(.{ .modifier = .always_inline }, c.update, .{input[0..aligned_len]});
+        return @call(.{ .modifier = .always_inline }, c.final, .{input[aligned_len..]});
+    }
+};
+
+/// Fast non-cryptographic 64bit hash function.
+/// See https://github.com/wangyi-fudan/wyhash
+pub const Wyhash = struct {
+    state: WyhashStateless,
+
+    buf: [32]u8,
+    buf_len: usize,
+
+    pub fn init(seed: u64) Wyhash {
+        return Wyhash{
+            .state = WyhashStateless.init(seed),
+            .buf = undefined,
+            .buf_len = 0,
+        };
+    }
+
+    pub fn update(self: *Wyhash, b: []const u8) void {
+        var off: usize = 0;
+
+        if (self.buf_len != 0 and self.buf_len + b.len >= 32) {
+            off += 32 - self.buf_len;
+            mem.copy(u8, self.buf[self.buf_len..], b[0..off]);
+            self.state.update(self.buf[0..]);
+            self.buf_len = 0;
+        }
+
+        const remain_len = b.len - off;
+        const aligned_len = remain_len - (remain_len % 32);
+        self.state.update(b[off .. off + aligned_len]);
+
+        mem.copy(u8, self.buf[self.buf_len..], b[off + aligned_len ..]);
+        self.buf_len += @intCast(u8, b[off + aligned_len ..].len);
+    }
+
+    pub fn final(self: *Wyhash) u64 {
+        const seed = self.state.seed;
+        const rem_len = @intCast(u5, self.buf_len);
+        const rem_key = self.buf[0..self.buf_len];
+
+        return self.state.final(rem_key);
+    }
+
+    pub fn hash(seed: u64, input: []const u8) u64 {
+        return WyhashStateless.hash(seed, input);
+    }
+};
+
+fn wyhash_hash(seed: u64, input: []const u8) u64 {
+    return Wyhash.hash(seed, input);
+}
+
+const expectEqual = std.testing.expectEqual;
+
+test "test vectors" {
+    const hash = Wyhash.hash;
+
+    expectEqual(hash(0, ""), 0x0);
+    expectEqual(hash(1, "a"), 0xbed235177f41d328);
+    expectEqual(hash(2, "abc"), 0xbe348debe59b27c3);
+    expectEqual(hash(3, "message digest"), 0x37320f657213a290);
+    expectEqual(hash(4, "abcdefghijklmnopqrstuvwxyz"), 0xd0b270e1d8a7019c);
+    expectEqual(hash(5, "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789"), 0x602a1894d3bbfe7f);
+    expectEqual(hash(6, "12345678901234567890123456789012345678901234567890123456789012345678901234567890"), 0x829e9c148b75970e);
+}
+
+test "test vectors streaming" {
+    var wh = Wyhash.init(5);
+    for ("ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789") |e| {
+        wh.update(mem.asBytes(&e));
+    }
+    expectEqual(wh.final(), 0x602a1894d3bbfe7f);
+
+    const pattern = "1234567890";
+    const count = 8;
+    const result = 0x829e9c148b75970e;
+    expectEqual(Wyhash.hash(6, pattern ** 8), result);
+
+    wh = Wyhash.init(6);
+    var i: u32 = 0;
+    while (i < count) : (i += 1) {
+        wh.update(pattern);
+    }
+    expectEqual(wh.final(), result);
+}
+
+test "iterative non-divisible update" {
+    var buf: [8192]u8 = undefined;
+    for (buf) |*e, i| {
+        e.* = @truncate(u8, i);
+    }
+
+    const seed = 0x128dad08f;
+
+    var end: usize = 32;
+    while (end < buf.len) : (end += 32) {
+        const non_iterative_hash = Wyhash.hash(seed, buf[0..end]);
+
+        var wy = Wyhash.init(seed);
+        var i: usize = 0;
+        while (i < end) : (i += 33) {
+            wy.update(buf[i..std.math.min(i + 33, end)]);
+        }
+        const iterative_hash = wy.final();
+
+        std.testing.expectEqual(iterative_hash, non_iterative_hash);
+    }
+}

compiler/builtins/bitcode/src/main.zig

@@ -2,6 +2,17 @@ const builtin = @import("builtin");
 const std = @import("std");
 const testing = std.testing;
 
+// Dict Module
+const dict = @import("dict.zig");
+const hash = @import("hash.zig");
+
+comptime {
+    exportDictFn(dict.dictLen, "len");
+    exportDictFn(dict.dictEmpty, "empty");
+    exportDictFn(hash.wyhash, "hash");
+    exportDictFn(hash.wyhash_rocstr, "hash_str");
+}
+
 // Num Module
 const num = @import("num.zig");
 comptime {
@@ -37,6 +48,9 @@ fn exportNumFn(comptime func: anytype, comptime func_name: []const u8) void {
 fn exportStrFn(comptime func: anytype, comptime func_name: []const u8) void {
     exportBuiltinFn(func, "str." ++ func_name);
 }
+fn exportDictFn(comptime func: anytype, comptime func_name: []const u8) void {
+    exportBuiltinFn(func, "dict." ++ func_name);
+}
 
 // Run all tests in imported modules
 // https://github.com/ziglang/zig/blob/master/lib/std/std.zig#L94

compiler/builtins/bitcode/src/str.zig

@@ -40,8 +40,6 @@ pub const RocStr = extern struct {
     // This clones the pointed-to bytes if they won't fit in a
     // small string, and returns a (pointer, len) tuple which points to them.
     pub fn init(allocator: *Allocator, bytes_ptr: [*]const u8, length: usize) RocStr {
-        const roc_str_size = @sizeOf(RocStr);
-
         var result = RocStr.allocate(allocator, InPlace.Clone, length);
         @memcpy(result.asU8ptr(), bytes_ptr, length);
 

compiler/builtins/docs/Dict.roc

@@ -1,7 +1,9 @@
-interface Dict2
+interface Dict
     exposes [ isEmpty, map ]
     imports []
 
+size : Dict * * -> Nat
+
 isEmpty : Dict * * -> Bool
 
 ## Convert each key and value in the #Dict to something new, by calling a conversion
@@ -13,4 +15,8 @@ isEmpty : Dict * * -> Bool
 ## 
 ## `map` functions like this are common in Roc, and they all work similarly.
 ## See for example #Result.map, #List.map, and #Set.map.
-map : List before, (before -> after) -> List after
+map :
+    Dict beforeKey beforeValue,
+    (\{ key: beforeKey, value: beforeValue } ->
+        { key: afterKey, value: afterValue }
+    ) -> Dict afterKey afterValue

compiler/builtins/src/bitcode.rs

@@ -34,3 +34,8 @@ pub const STR_ENDS_WITH: &str = "roc_builtins.str.ends_with";
 pub const STR_NUMBER_OF_BYTES: &str = "roc_builtins.str.number_of_bytes";
 pub const STR_FROM_INT: &str = "roc_builtins.str.from_int";
 pub const STR_EQUAL: &str = "roc_builtins.str.equal";
+
+pub const DICT_HASH: &str = "roc_builtins.dict.hash";
+pub const DICT_HASH_STR: &str = "roc_builtins.dict.hash_str";
+pub const DICT_LEN: &str = "roc_builtins.dict.len";
+pub const DICT_EMPTY: &str = "roc_builtins.dict.empty";

compiler/builtins/src/std.rs

@@ -4,7 +4,7 @@ use roc_module::symbol::Symbol;
 use roc_region::all::Region;
 use roc_types::builtin_aliases::{
     bool_type, dict_type, float_type, int_type, list_type, nat_type, num_type, ordering_type,
-    result_type, set_type, str_type,
+    result_type, set_type, str_type, u64_type,
 };
 use roc_types::solved_types::SolvedType;
 use roc_types::subs::VarId;
@@ -729,7 +729,22 @@ pub fn types() -> MutMap<Symbol, (SolvedType, Region)> {
 
     // Dict module
 
-    // empty : Dict k v
+    // Dict.hashTestOnly : Nat, v -> Nat
+    add_type(
+        Symbol::DICT_TEST_HASH,
+        top_level_function(vec![u64_type(), flex(TVAR2)], Box::new(nat_type())),
+    );
+
+    // len : Dict * * -> Nat
+    add_type(
+        Symbol::DICT_LEN,
+        top_level_function(
+            vec![dict_type(flex(TVAR1), flex(TVAR2))],
+            Box::new(nat_type()),
+        ),
+    );
+
+    // empty : Dict * *
     add_type(Symbol::DICT_EMPTY, dict_type(flex(TVAR1), flex(TVAR2)));
 
     // singleton : k, v -> Dict k v

compiler/builtins/src/unique.rs

@@ -906,6 +906,13 @@ pub fn types() -> MutMap<Symbol, (SolvedType, Region)> {
 
     // Dict module
 
+    //  : Attr * (Dict k v) -> Attr * Nat
+    add_type(Symbol::DICT_LEN, {
+        let_tvars! { star1, k , v, star2, int };
+
+        unique_function(vec![dict_type(star1, k, v)], int_type(star2, int))
+    });
+
     // empty : Attr * (Dict k v)
     add_type(Symbol::DICT_EMPTY, {
         let_tvars! { star, k , v };

compiler/can/src/builtins.rs

@@ -79,6 +79,10 @@ pub fn builtin_defs_map(symbol: Symbol, var_store: &mut VarStore) -> Option<Def>
         LIST_KEEP_IF => list_keep_if,
         LIST_WALK => list_walk,
         LIST_WALK_BACKWARDS => list_walk_backwards,
+        DICT_TEST_HASH => dict_hash_test_only,
+        DICT_LEN => dict_len,
+        DICT_EMPTY => dict_empty,
+        DICT_INSERT => dict_insert,
         NUM_ADD => num_add,
         NUM_ADD_CHECKED => num_add_checked,
         NUM_ADD_WRAP => num_add_wrap,
@@ -174,6 +178,10 @@ pub fn builtin_defs(var_store: &mut VarStore) -> MutMap<Symbol, Def> {
         Symbol::LIST_KEEP_IF => list_keep_if,
         Symbol::LIST_WALK => list_walk,
         Symbol::LIST_WALK_BACKWARDS => list_walk_backwards,
+        Symbol::DICT_TEST_HASH => dict_hash_test_only,
+        Symbol::DICT_LEN => dict_len,
+        Symbol::DICT_EMPTY => dict_empty,
+        Symbol::DICT_INSERT => dict_insert,
         Symbol::NUM_ADD => num_add,
         Symbol::NUM_ADD_CHECKED => num_add_checked,
         Symbol::NUM_ADD_WRAP => num_add_wrap,
@@ -1780,7 +1788,7 @@ fn list_keep_if(symbol: Symbol, var_store: &mut VarStore) -> Def {
     )
 }
 
-// List.contains : List elem, elem, -> Bool
+/// List.contains : List elem, elem -> Bool
 fn list_contains(symbol: Symbol, var_store: &mut VarStore) -> Def {
     let list_var = var_store.fresh();
     let elem_var = var_store.fresh();
@@ -1828,6 +1836,97 @@ fn list_map(symbol: Symbol, var_store: &mut VarStore) -> Def {
     )
 }
 
+/// Dict.hashTestOnly : k, v -> Nat
+pub fn dict_hash_test_only(symbol: Symbol, var_store: &mut VarStore) -> Def {
+    let key_var = var_store.fresh();
+    let value_var = var_store.fresh();
+    let nat_var = var_store.fresh();
+
+    let body = RunLowLevel {
+        op: LowLevel::Hash,
+        args: vec![
+            (key_var, Var(Symbol::ARG_1)),
+            (value_var, Var(Symbol::ARG_2)),
+        ],
+        ret_var: nat_var,
+    };
+
+    defn(
+        symbol,
+        vec![(key_var, Symbol::ARG_1), (value_var, Symbol::ARG_2)],
+        var_store,
+        body,
+        nat_var,
+    )
+}
+
+/// Dict.len : Dict * * -> Nat
+fn dict_len(symbol: Symbol, var_store: &mut VarStore) -> Def {
+    let size_var = var_store.fresh();
+    let dict_var = var_store.fresh();
+
+    let body = RunLowLevel {
+        op: LowLevel::DictSize,
+        args: vec![(dict_var, Var(Symbol::ARG_1))],
+        ret_var: size_var,
+    };
+
+    defn(
+        symbol,
+        vec![(dict_var, Symbol::ARG_1)],
+        var_store,
+        body,
+        size_var,
+    )
+}
+
+/// Dict.empty : Dict * *
+fn dict_empty(symbol: Symbol, var_store: &mut VarStore) -> Def {
+    let dict_var = var_store.fresh();
+    let body = RunLowLevel {
+        op: LowLevel::DictEmpty,
+        args: vec![],
+        ret_var: dict_var,
+    };
+
+    Def {
+        annotation: None,
+        expr_var: dict_var,
+        loc_expr: Located::at_zero(body),
+        loc_pattern: Located::at_zero(Pattern::Identifier(symbol)),
+        pattern_vars: SendMap::default(),
+    }
+}
+
+/// Dict.insert : Dict k v, k, v -> Dict k v
+fn dict_insert(symbol: Symbol, var_store: &mut VarStore) -> Def {
+    let dict_var = var_store.fresh();
+    let key_var = var_store.fresh();
+    let val_var = var_store.fresh();
+
+    let body = RunLowLevel {
+        op: LowLevel::DictInsert,
+        args: vec![
+            (dict_var, Var(Symbol::ARG_1)),
+            (key_var, Var(Symbol::ARG_2)),
+            (val_var, Var(Symbol::ARG_3)),
+        ],
+        ret_var: dict_var,
+    };
+
+    defn(
+        symbol,
+        vec![
+            (dict_var, Symbol::ARG_1),
+            (key_var, Symbol::ARG_2),
+            (val_var, Symbol::ARG_3),
+        ],
+        var_store,
+        body,
+        dict_var,
+    )
+}
+
 /// Num.rem : Int, Int -> Result Int [ DivByZero ]*
 fn num_rem(symbol: Symbol, var_store: &mut VarStore) -> Def {
     let num_var = var_store.fresh();

compiler/can/src/module.rs

@@ -1,4 +1,3 @@
-use crate::builtins;
 use crate::def::{canonicalize_defs, sort_can_defs, Declaration, Def};
 use crate::env::Env;
 use crate::expr::{Expr, Output};
@@ -41,7 +40,7 @@ pub struct ModuleOutput {
 
 // TODO trim these down
 #[allow(clippy::too_many_arguments)]
-pub fn canonicalize_module_defs<'a>(
+pub fn canonicalize_module_defs<'a, F>(
     arena: &Bump,
     loc_defs: &'a [Located<ast::Def<'a>>],
     home: ModuleId,
@@ -52,7 +51,11 @@ pub fn canonicalize_module_defs<'a>(
     exposed_imports: MutMap<Ident, (Symbol, Region)>,
     exposed_symbols: &MutSet<Symbol>,
     var_store: &mut VarStore,
-) -> Result<ModuleOutput, RuntimeError> {
+    look_up_builtin: F,
+) -> Result<ModuleOutput, RuntimeError>
+where
+    F: Fn(Symbol, &mut VarStore) -> Option<Def> + 'static + Send + Copy,
+{
     let mut can_exposed_imports = MutMap::default();
     let mut scope = Scope::new(home, var_store);
     let num_deps = dep_idents.len();
@@ -284,7 +287,7 @@ pub fn canonicalize_module_defs<'a>(
             for symbol in references.iter() {
                 if symbol.is_builtin() {
                     // this can fail when the symbol is for builtin types, or has no implementation yet
-                    if let Some(def) = builtins::builtin_defs_map(*symbol, var_store) {
+                    if let Some(def) = look_up_builtin(*symbol, var_store) {
                         declarations.push(Declaration::Builtin(def));
                     }
                 }

compiler/can/tests/test_can.rs

@@ -967,6 +967,21 @@ mod test_can {
         }
     }
 
+    #[test]
+    fn dict() {
+        let src = indoc!(
+            r#"
+                x = Dict.empty
+                
+                Dict.len x
+            "#
+        );
+        let arena = Bump::new();
+        let CanExprOut { problems, .. } = can_expr_with(&arena, test_home(), src);
+
+        assert_eq!(problems, Vec::new());
+    }
+
     #[test]
     fn unused_def_regression() {
         let src = indoc!(

compiler/gen/src/llvm/build.rs

@@ -1,3 +1,5 @@
+use crate::llvm::build_dict::{dict_empty, dict_insert, dict_len};
+use crate::llvm::build_hash::generic_hash;
 use crate::llvm::build_list::{
     allocate_list, empty_list, empty_polymorphic_list, list_append, list_concat, list_contains,
     list_get_unsafe, list_join, list_keep_if, list_len, list_map, list_prepend, list_repeat,
@@ -7,7 +9,7 @@ use crate::llvm::build_str::{
     str_concat, str_count_graphemes, str_ends_with, str_from_int, str_join_with,
     str_number_of_bytes, str_split, str_starts_with, CHAR_LAYOUT,
 };
-use crate::llvm::compare::{generic_eq, generic_neq};
+use crate::llvm::compare::{build_eq, build_neq, generic_eq, generic_neq};
 use crate::llvm::convert::{
     basic_type_from_builtin, basic_type_from_layout, block_of_memory, block_of_memory_slices,
     collection, get_fn_type, get_ptr_type, ptr_int,
@@ -3978,6 +3980,31 @@ fn run_low_level<'a, 'ctx, 'env>(
                 empty,
             )
         }
+        Hash => {
+            debug_assert_eq!(args.len(), 2);
+            let seed = load_symbol(scope, &args[0]);
+            let (value, layout) = load_symbol_and_layout(scope, &args[1]);
+
+            debug_assert!(seed.is_int_value());
+
+            generic_hash(env, layout_ids, seed.into_int_value(), value, layout).into()
+        }
+        DictSize => {
+            debug_assert_eq!(args.len(), 1);
+            dict_len(env, scope, args[0])
+        }
+        DictEmpty => {
+            debug_assert_eq!(args.len(), 0);
+            dict_empty(env, scope)
+        }
+        DictInsert => {
+            debug_assert_eq!(args.len(), 3);
+
+            let (dict, _) = load_symbol_and_layout(scope, &args[0]);
+            let (key, key_layout) = load_symbol_and_layout(scope, &args[1]);
+            let (value, value_layout) = load_symbol_and_layout(scope, &args[2]);
+            dict_insert(env, scope, dict, key, key_layout, value, value_layout)
+        }
     }
 }
 

compiler/gen/src/llvm/build_dict.rs

@@ -0,0 +1,110 @@
+use crate::llvm::build::{
+    call_bitcode_fn, call_void_bitcode_fn, complex_bitcast, load_symbol, load_symbol_and_layout,
+    Env, Scope,
+};
+use crate::llvm::convert::collection;
+use inkwell::types::BasicTypeEnum;
+use inkwell::values::{BasicValueEnum, IntValue, StructValue};
+use inkwell::AddressSpace;
+use roc_builtins::bitcode;
+use roc_module::symbol::Symbol;
+use roc_mono::layout::{Builtin, Layout};
+
+pub fn dict_len<'a, 'ctx, 'env>(
+    env: &Env<'a, 'ctx, 'env>,
+    scope: &Scope<'a, 'ctx>,
+    dict_symbol: Symbol,
+) -> BasicValueEnum<'ctx> {
+    let ctx = env.context;
+
+    let (_, dict_layout) = load_symbol_and_layout(scope, &dict_symbol);
+
+    match dict_layout {
+        Layout::Builtin(Builtin::Dict(_, _)) => {
+            let dict_as_int = dict_symbol_to_i128(env, scope, dict_symbol);
+
+            call_bitcode_fn(env, &[dict_as_int.into()], &bitcode::DICT_LEN)
+        }
+        Layout::Builtin(Builtin::EmptyDict) => ctx.i64_type().const_zero().into(),
+        _ => unreachable!("Invalid layout given to Dict.len : {:?}", dict_layout),
+    }
+}
+
+pub fn dict_empty<'a, 'ctx, 'env>(
+    env: &Env<'a, 'ctx, 'env>,
+    _scope: &Scope<'a, 'ctx>,
+) -> BasicValueEnum<'ctx> {
+    // get the RocDict type defined by zig
+    let roc_dict_type = env.module.get_struct_type("dict.RocDict").unwrap();
+
+    // we must give a pointer for the bitcode function to write the result into
+    let result_alloc = env.builder.build_alloca(roc_dict_type, "dict_empty");
+
+    call_void_bitcode_fn(env, &[result_alloc.into()], &bitcode::DICT_EMPTY);
+
+    let result = env
+        .builder
+        .build_load(result_alloc, "load_result")
+        .into_struct_value();
+
+    zig_dict_to_struct(env, result).into()
+}
+
+pub fn dict_insert<'a, 'ctx, 'env>(
+    _env: &Env<'a, 'ctx, 'env>,
+    _scope: &Scope<'a, 'ctx>,
+    _dict: BasicValueEnum<'ctx>,
+    _key: BasicValueEnum<'ctx>,
+    _key_layout: &Layout<'a>,
+    _value: BasicValueEnum<'ctx>,
+    _value_layout: &Layout<'a>,
+) -> BasicValueEnum<'ctx> {
+    todo!()
+}
+
+fn dict_symbol_to_i128<'a, 'ctx, 'env>(
+    env: &Env<'a, 'ctx, 'env>,
+    scope: &Scope<'a, 'ctx>,
+    symbol: Symbol,
+) -> IntValue<'ctx> {
+    let dict = load_symbol(scope, &symbol);
+
+    let i128_type = env.context.i128_type().into();
+
+    complex_bitcast(&env.builder, dict, i128_type, "dict_to_i128").into_int_value()
+}
+
+fn zig_dict_to_struct<'a, 'ctx, 'env>(
+    env: &Env<'a, 'ctx, 'env>,
+    zig_dict: StructValue<'ctx>,
+) -> StructValue<'ctx> {
+    let builder = env.builder;
+
+    // get the RocStr type defined by zig
+    let zig_str_type = env.module.get_struct_type("dict.RocDict").unwrap();
+
+    let ret_type = BasicTypeEnum::StructType(collection(env.context, env.ptr_bytes));
+
+    // a roundabout way of casting (LLVM does not accept a standard bitcast)
+    let allocation = builder.build_alloca(zig_str_type, "zig_result");
+
+    builder.build_store(allocation, zig_dict);
+
+    let ptr3 = builder
+        .build_bitcast(
+            allocation,
+            env.context.i128_type().ptr_type(AddressSpace::Generic),
+            "cast",
+        )
+        .into_pointer_value();
+
+    let ptr4 = builder
+        .build_bitcast(
+            ptr3,
+            ret_type.into_struct_type().ptr_type(AddressSpace::Generic),
+            "cast",
+        )
+        .into_pointer_value();
+
+    builder.build_load(ptr4, "load").into_struct_value()
+}

compiler/gen/src/llvm/build_hash.rs

@@ -0,0 +1,945 @@
+use crate::llvm::build::Env;
+use crate::llvm::build::{
+    call_bitcode_fn, cast_block_of_memory_to_tag, complex_bitcast, set_name, FAST_CALL_CONV,
+};
+use crate::llvm::build_str;
+use crate::llvm::convert::basic_type_from_layout;
+use bumpalo::collections::Vec;
+use inkwell::values::{BasicValueEnum, FunctionValue, IntValue, PointerValue, StructValue};
+use roc_builtins::bitcode;
+use roc_module::symbol::Symbol;
+use roc_mono::layout::{Builtin, Layout, LayoutIds, UnionLayout};
+
+#[derive(Clone, Debug)]
+enum WhenRecursive<'a> {
+    Unreachable,
+    Loop(UnionLayout<'a>),
+}
+
+pub fn generic_hash<'a, 'ctx, 'env>(
+    env: &Env<'a, 'ctx, 'env>,
+    layout_ids: &mut LayoutIds<'a>,
+    seed: IntValue<'ctx>,
+    val: BasicValueEnum<'ctx>,
+    layout: &Layout<'a>,
+) -> IntValue<'ctx> {
+    // NOTE: C and Zig use this value for their initial HashMap seed: 0xc70f6907
+    build_hash_layout(
+        env,
+        layout_ids,
+        seed,
+        val,
+        layout,
+        WhenRecursive::Unreachable,
+    )
+}
+
+fn build_hash_layout<'a, 'ctx, 'env>(
+    env: &Env<'a, 'ctx, 'env>,
+    layout_ids: &mut LayoutIds<'a>,
+    seed: IntValue<'ctx>,
+    val: BasicValueEnum<'ctx>,
+    layout: &Layout<'a>,
+    when_recursive: WhenRecursive<'a>,
+) -> IntValue<'ctx> {
+    match layout {
+        Layout::Builtin(builtin) => {
+            hash_builtin(env, layout_ids, seed, val, layout, builtin, when_recursive)
+        }
+
+        Layout::Struct(fields) => build_hash_struct(
+            env,
+            layout_ids,
+            fields,
+            when_recursive,
+            seed,
+            val.into_struct_value(),
+        ),
+
+        Layout::PhantomEmptyStruct => {
+            // just does nothing and returns the seed
+            seed
+        }
+
+        Layout::Union(union_layout) => {
+            build_hash_tag(env, layout_ids, layout, union_layout, seed, val)
+        }
+
+        Layout::RecursivePointer => match when_recursive {
+            WhenRecursive::Unreachable => {
+                unreachable!("recursion pointers should never be hashed directly")
+            }
+            WhenRecursive::Loop(union_layout) => {
+                let layout = Layout::Union(union_layout.clone());
+
+                let bt = basic_type_from_layout(env.arena, env.context, &layout, env.ptr_bytes);
+
+                // cast the i64 pointer to a pointer to block of memory
+                let field_cast = env
+                    .builder
+                    .build_bitcast(val, bt, "i64_to_opaque")
+                    .into_pointer_value();
+
+                build_hash_tag(
+                    env,
+                    layout_ids,
+                    &layout,
+                    &union_layout,
+                    seed,
+                    field_cast.into(),
+                )
+            }
+        },
+
+        Layout::Pointer(_) => {
+            unreachable!("unused")
+        }
+
+        Layout::FunctionPointer(_, _) | Layout::Closure(_, _, _) => {
+            unreachable!("the type system will guarantee these are never hashed")
+        }
+    }
+}
+
+fn append_hash_layout<'a, 'ctx, 'env>(
+    env: &Env<'a, 'ctx, 'env>,
+    layout_ids: &mut LayoutIds<'a>,
+    seed: IntValue<'ctx>,
+    val: BasicValueEnum<'ctx>,
+    layout: &Layout<'a>,
+    when_recursive: WhenRecursive<'a>,
+) -> IntValue<'ctx> {
+    build_hash_layout(env, layout_ids, seed, val, layout, when_recursive)
+}
+
+fn hash_builtin<'a, 'ctx, 'env>(
+    env: &Env<'a, 'ctx, 'env>,
+    layout_ids: &mut LayoutIds<'a>,
+    seed: IntValue<'ctx>,
+    val: BasicValueEnum<'ctx>,
+    layout: &Layout<'a>,
+    builtin: &Builtin<'a>,
+    when_recursive: WhenRecursive<'a>,
+) -> IntValue<'ctx> {
+    let ptr_bytes = env.ptr_bytes;
+
+    match builtin {
+        Builtin::Int128
+        | Builtin::Int64
+        | Builtin::Int32
+        | Builtin::Int16
+        | Builtin::Int8
+        | Builtin::Int1
+        | Builtin::Float64
+        | Builtin::Float32
+        | Builtin::Float128
+        | Builtin::Float16
+        | Builtin::Usize => {
+            let hash_bytes = store_and_use_as_u8_ptr(env, val, &layout);
+            hash_bitcode_fn(env, seed, hash_bytes, layout.stack_size(ptr_bytes))
+        }
+        Builtin::Str => {
+            // let zig deal with big vs small string
+            call_bitcode_fn(
+                env,
+                &[seed.into(), build_str::str_to_i128(env, val).into()],
+                &bitcode::DICT_HASH_STR,
+            )
+            .into_int_value()
+        }
+        Builtin::EmptyStr | Builtin::EmptyDict | Builtin::EmptyList | Builtin::EmptySet => {
+            hash_empty_collection(seed)
+        }
+
+        Builtin::Dict(_, _) => {
+            todo!("Implement hash for Dict")
+        }
+        Builtin::Set(_) => {
+            todo!("Implement Hash for Set")
+        }
+        Builtin::List(_, element_layout) => build_hash_list(
+            env,
+            layout_ids,
+            layout,
+            element_layout,
+            when_recursive,
+            seed,
+            val.into_struct_value(),
+        ),
+    }
+}
+
+fn build_hash_struct<'a, 'ctx, 'env>(
+    env: &Env<'a, 'ctx, 'env>,
+    layout_ids: &mut LayoutIds<'a>,
+    field_layouts: &'a [Layout<'a>],
+    when_recursive: WhenRecursive<'a>,
+    seed: IntValue<'ctx>,
+    value: StructValue<'ctx>,
+) -> IntValue<'ctx> {
+    let block = env.builder.get_insert_block().expect("to be in a function");
+    let di_location = env.builder.get_current_debug_location().unwrap();
+
+    let struct_layout = Layout::Struct(field_layouts);
+
+    let symbol = Symbol::GENERIC_HASH;
+    let fn_name = layout_ids
+        .get(symbol, &struct_layout)
+        .to_symbol_string(symbol, &env.interns);
+
+    let function = match env.module.get_function(fn_name.as_str()) {
+        Some(function_value) => function_value,
+        None => {
+            let arena = env.arena;
+
+            let seed_type = env.context.i64_type();
+
+            let arg_type =
+                basic_type_from_layout(arena, env.context, &struct_layout, env.ptr_bytes);
+
+            let function_value = crate::llvm::refcounting::build_header_help(
+                env,
+                &fn_name,
+                seed_type.into(),
+                &[seed_type.into(), arg_type],
+            );
+
+            build_hash_struct_help(
+                env,
+                layout_ids,
+                function_value,
+                when_recursive,
+                field_layouts,
+            );
+
+            function_value
+        }
+    };
+
+    env.builder.position_at_end(block);
+    env.builder
+        .set_current_debug_location(env.context, di_location);
+    let call = env
+        .builder
+        .build_call(function, &[seed.into(), value.into()], "struct_hash");
+
+    call.set_call_convention(FAST_CALL_CONV);
+
+    call.try_as_basic_value().left().unwrap().into_int_value()
+}
+
+fn build_hash_struct_help<'a, 'ctx, 'env>(
+    env: &Env<'a, 'ctx, 'env>,
+    layout_ids: &mut LayoutIds<'a>,
+    parent: FunctionValue<'ctx>,
+    when_recursive: WhenRecursive<'a>,
+    field_layouts: &[Layout<'a>],
+) {
+    let ctx = env.context;
+    let builder = env.builder;
+
+    {
+        use inkwell::debug_info::AsDIScope;
+
+        let func_scope = parent.get_subprogram().unwrap();
+        let lexical_block = env.dibuilder.create_lexical_block(
+            /* scope */ func_scope.as_debug_info_scope(),
+            /* file */ env.compile_unit.get_file(),
+            /* line_no */ 0,
+            /* column_no */ 0,
+        );
+
+        let loc = env.dibuilder.create_debug_location(
+            ctx,
+            /* line */ 0,
+            /* column */ 0,
+            /* current_scope */ lexical_block.as_debug_info_scope(),
+            /* inlined_at */ None,
+        );
+        builder.set_current_debug_location(&ctx, loc);
+    }
+
+    // Add args to scope
+    let mut it = parent.get_param_iter();
+    let seed = it.next().unwrap().into_int_value();
+    let value = it.next().unwrap().into_struct_value();
+
+    set_name(seed.into(), Symbol::ARG_1.ident_string(&env.interns));
+    set_name(value.into(), Symbol::ARG_2.ident_string(&env.interns));
+
+    let entry = ctx.append_basic_block(parent, "entry");
+    env.builder.position_at_end(entry);
+
+    let result = hash_struct(env, layout_ids, seed, value, when_recursive, field_layouts);
+
+    env.builder.build_return(Some(&result));
+}
+
+fn hash_struct<'a, 'ctx, 'env>(
+    env: &Env<'a, 'ctx, 'env>,
+    layout_ids: &mut LayoutIds<'a>,
+    mut seed: IntValue<'ctx>,
+    value: StructValue<'ctx>,
+    when_recursive: WhenRecursive<'a>,
+    field_layouts: &[Layout<'a>],
+) -> IntValue<'ctx> {
+    let ptr_bytes = env.ptr_bytes;
+
+    let layout = Layout::Struct(field_layouts);
+
+    // Optimization: if the bit representation of equal values is the same
+    // just hash the bits. Caveat here is tags: e.g. `Nothing` in `Just a`
+    // contains garbage bits after the tag (currently)
+    if false {
+        // this is a struct of only basic types, so we can just hash its bits
+        let hash_bytes = store_and_use_as_u8_ptr(env, value.into(), &layout);
+        hash_bitcode_fn(env, seed, hash_bytes, layout.stack_size(ptr_bytes))
+    } else {
+        for (index, field_layout) in field_layouts.iter().enumerate() {
+            let field = env
+                .builder
+                .build_extract_value(value, index as u32, "eq_field")
+                .unwrap();
+
+            if let Layout::RecursivePointer = field_layout {
+                match &when_recursive {
+                    WhenRecursive::Unreachable => {
+                        unreachable!("The current layout should not be recursive, but is")
+                    }
+                    WhenRecursive::Loop(union_layout) => {
+                        let field_layout = Layout::Union(union_layout.clone());
+
+                        let bt = basic_type_from_layout(
+                            env.arena,
+                            env.context,
+                            &field_layout,
+                            env.ptr_bytes,
+                        );
+
+                        // cast the i64 pointer to a pointer to block of memory
+                        let field_cast = env
+                            .builder
+                            .build_bitcast(field, bt, "i64_to_opaque")
+                            .into_pointer_value();
+
+                        seed = append_hash_layout(
+                            env,
+                            layout_ids,
+                            seed,
+                            field_cast.into(),
+                            &field_layout,
+                            when_recursive.clone(),
+                        )
+                    }
+                }
+            } else {
+                seed = append_hash_layout(
+                    env,
+                    layout_ids,
+                    seed,
+                    field,
+                    field_layout,
+                    when_recursive.clone(),
+                );
+            }
+        }
+        seed
+    }
+}
+
+fn build_hash_tag<'a, 'ctx, 'env>(
+    env: &Env<'a, 'ctx, 'env>,
+    layout_ids: &mut LayoutIds<'a>,
+    layout: &Layout<'a>,
+    union_layout: &UnionLayout<'a>,
+    seed: IntValue<'ctx>,
+    value: BasicValueEnum<'ctx>,
+) -> IntValue<'ctx> {
+    let block = env.builder.get_insert_block().expect("to be in a function");
+    let di_location = env.builder.get_current_debug_location().unwrap();
+
+    let symbol = Symbol::GENERIC_HASH;
+    let fn_name = layout_ids
+        .get(symbol, &layout)
+        .to_symbol_string(symbol, &env.interns);
+
+    let function = match env.module.get_function(fn_name.as_str()) {
+        Some(function_value) => function_value,
+        None => {
+            let arena = env.arena;
+
+            let seed_type = env.context.i64_type();
+
+            let arg_type = basic_type_from_layout(arena, env.context, &layout, env.ptr_bytes);
+
+            let function_value = crate::llvm::refcounting::build_header_help(
+                env,
+                &fn_name,
+                seed_type.into(),
+                &[seed_type.into(), arg_type],
+            );
+
+            build_hash_tag_help(env, layout_ids, function_value, union_layout);
+
+            function_value
+        }
+    };
+
+    env.builder.position_at_end(block);
+    env.builder
+        .set_current_debug_location(env.context, di_location);
+    let call = env
+        .builder
+        .build_call(function, &[seed.into(), value], "struct_hash");
+
+    call.set_call_convention(FAST_CALL_CONV);
+
+    call.try_as_basic_value().left().unwrap().into_int_value()
+}
+
+fn build_hash_tag_help<'a, 'ctx, 'env>(
+    env: &Env<'a, 'ctx, 'env>,
+    layout_ids: &mut LayoutIds<'a>,
+    parent: FunctionValue<'ctx>,
+    union_layout: &UnionLayout<'a>,
+) {
+    let ctx = env.context;
+    let builder = env.builder;
+
+    {
+        use inkwell::debug_info::AsDIScope;
+
+        let func_scope = parent.get_subprogram().unwrap();
+        let lexical_block = env.dibuilder.create_lexical_block(
+            /* scope */ func_scope.as_debug_info_scope(),
+            /* file */ env.compile_unit.get_file(),
+            /* line_no */ 0,
+            /* column_no */ 0,
+        );
+
+        let loc = env.dibuilder.create_debug_location(
+            ctx,
+            /* line */ 0,
+            /* column */ 0,
+            /* current_scope */ lexical_block.as_debug_info_scope(),
+            /* inlined_at */ None,
+        );
+        builder.set_current_debug_location(&ctx, loc);
+    }
+
+    // Add args to scope
+    let mut it = parent.get_param_iter();
+    let seed = it.next().unwrap().into_int_value();
+    let value = it.next().unwrap();
+
+    set_name(seed.into(), Symbol::ARG_1.ident_string(&env.interns));
+    set_name(value, Symbol::ARG_2.ident_string(&env.interns));
+
+    let entry = ctx.append_basic_block(parent, "entry");
+    env.builder.position_at_end(entry);
+
+    let result = hash_tag(env, layout_ids, parent, seed, value, union_layout);
+
+    env.builder.build_return(Some(&result));
+}
+
+fn hash_tag<'a, 'ctx, 'env>(
+    env: &Env<'a, 'ctx, 'env>,
+    layout_ids: &mut LayoutIds<'a>,
+    parent: FunctionValue<'ctx>,
+    seed: IntValue<'ctx>,
+    tag: BasicValueEnum<'ctx>,
+    union_layout: &UnionLayout<'a>,
+) -> IntValue<'ctx> {
+    use UnionLayout::*;
+
+    let entry_block = env.builder.get_insert_block().unwrap();
+
+    let merge_block = env.context.append_basic_block(parent, "merge_block");
+    env.builder.position_at_end(merge_block);
+
+    let merge_phi = env.builder.build_phi(env.context.i64_type(), "merge_hash");
+
+    env.builder.position_at_end(entry_block);
+    match union_layout {
+        NonRecursive(tags) => {
+            // SAFETY we know that non-recursive tags cannot be NULL
+            let tag_id = nonrec_tag_id(env, tag.into_struct_value());
+
+            let mut cases = Vec::with_capacity_in(tags.len(), env.arena);
+
+            for (tag_id, field_layouts) in tags.iter().enumerate() {
+                let block = env.context.append_basic_block(parent, "tag_id_modify");
+                env.builder.position_at_end(block);
+
+                // TODO drop tag id?
+                let struct_layout = Layout::Struct(field_layouts);
+
+                let wrapper_type =
+                    basic_type_from_layout(env.arena, env.context, &struct_layout, env.ptr_bytes);
+                debug_assert!(wrapper_type.is_struct_type());
+
+                let as_struct =
+                    cast_block_of_memory_to_tag(env.builder, tag.into_struct_value(), wrapper_type);
+
+                let answer = build_hash_struct(
+                    env,
+                    layout_ids,
+                    field_layouts,
+                    WhenRecursive::Unreachable,
+                    seed,
+                    as_struct,
+                );
+
+                merge_phi.add_incoming(&[(&answer, block)]);
+                env.builder.build_unconditional_branch(merge_block);
+
+                cases.push((
+                    env.context.i64_type().const_int(tag_id as u64, false),
+                    block,
+                ));
+            }
+
+            env.builder.position_at_end(entry_block);
+
+            let default = cases.pop().unwrap().1;
+
+            env.builder.build_switch(tag_id, default, &cases);
+        }
+        Recursive(tags) => {
+            // SAFETY recursive tag unions are not NULL
+            let tag_id = unsafe { rec_tag_id_unsafe(env, tag.into_pointer_value()) };
+
+            let mut cases = Vec::with_capacity_in(tags.len(), env.arena);
+
+            for (tag_id, field_layouts) in tags.iter().enumerate() {
+                let block = env.context.append_basic_block(parent, "tag_id_modify");
+                env.builder.position_at_end(block);
+
+                let answer = hash_ptr_to_struct(
+                    env,
+                    layout_ids,
+                    union_layout,
+                    field_layouts,
+                    seed,
+                    tag.into_pointer_value(),
+                );
+
+                merge_phi.add_incoming(&[(&answer, block)]);
+                env.builder.build_unconditional_branch(merge_block);
+
+                cases.push((
+                    env.context.i64_type().const_int(tag_id as u64, false),
+                    block,
+                ));
+            }
+
+            env.builder.position_at_end(entry_block);
+
+            let default = cases.pop().unwrap().1;
+
+            env.builder.build_switch(tag_id, default, &cases);
+        }
+        NullableUnwrapped { other_fields, .. } => {
+            let tag = tag.into_pointer_value();
+            let other_fields = &other_fields[1..];
+
+            let is_null = env.builder.build_is_null(tag, "is_null");
+
+            let hash_null_block = env.context.append_basic_block(parent, "hash_null_block");
+            let hash_other_block = env.context.append_basic_block(parent, "hash_other_block");
+
+            env.builder
+                .build_conditional_branch(is_null, hash_null_block, hash_other_block);
+
+            {
+                env.builder.position_at_end(hash_null_block);
+
+                let answer = hash_null(seed);
+
+                merge_phi.add_incoming(&[(&answer, hash_null_block)]);
+                env.builder.build_unconditional_branch(merge_block);
+            }
+
+            {
+                env.builder.position_at_end(hash_other_block);
+
+                let answer =
+                    hash_ptr_to_struct(env, layout_ids, union_layout, other_fields, seed, tag);
+
+                merge_phi.add_incoming(&[(&answer, hash_other_block)]);
+                env.builder.build_unconditional_branch(merge_block);
+            }
+        }
+        NullableWrapped { other_tags, .. } => {
+            let tag = tag.into_pointer_value();
+
+            let is_null = env.builder.build_is_null(tag, "is_null");
+
+            let hash_null_block = env.context.append_basic_block(parent, "hash_null_block");
+            let hash_other_block = env.context.append_basic_block(parent, "hash_other_block");
+
+            env.builder
+                .build_conditional_branch(is_null, hash_null_block, hash_other_block);
+
+            {
+                env.builder.position_at_end(hash_null_block);
+
+                let answer = hash_null(seed);
+
+                merge_phi.add_incoming(&[(&answer, hash_null_block)]);
+                env.builder.build_unconditional_branch(merge_block);
+            }
+
+            {
+                env.builder.position_at_end(hash_other_block);
+
+                // SAFETY recursive tag unions are not NULL
+                let tag_id = unsafe { rec_tag_id_unsafe(env, tag) };
+
+                let mut cases = Vec::with_capacity_in(other_tags.len(), env.arena);
+
+                for (tag_id, field_layouts) in other_tags.iter().enumerate() {
+                    let block = env.context.append_basic_block(parent, "tag_id_modify");
+                    env.builder.position_at_end(block);
+
+                    let answer =
+                        hash_ptr_to_struct(env, layout_ids, union_layout, field_layouts, seed, tag);
+
+                    merge_phi.add_incoming(&[(&answer, block)]);
+                    env.builder.build_unconditional_branch(merge_block);
+
+                    cases.push((
+                        env.context.i64_type().const_int(tag_id as u64, false),
+                        block,
+                    ));
+                }
+
+                env.builder.position_at_end(hash_other_block);
+
+                let default = cases.pop().unwrap().1;
+
+                env.builder.build_switch(tag_id, default, &cases);
+            }
+        }
+        NonNullableUnwrapped(field_layouts) => {
+            let answer = hash_ptr_to_struct(
+                env,
+                layout_ids,
+                union_layout,
+                field_layouts,
+                seed,
+                tag.into_pointer_value(),
+            );
+
+            merge_phi.add_incoming(&[(&answer, entry_block)]);
+            env.builder.build_unconditional_branch(merge_block);
+        }
+    }
+
+    env.builder.position_at_end(merge_block);
+
+    merge_phi.as_basic_value().into_int_value()
+}
+
+fn build_hash_list<'a, 'ctx, 'env>(
+    env: &Env<'a, 'ctx, 'env>,
+    layout_ids: &mut LayoutIds<'a>,
+    layout: &Layout<'a>,
+    element_layout: &Layout<'a>,
+    when_recursive: WhenRecursive<'a>,
+    seed: IntValue<'ctx>,
+    value: StructValue<'ctx>,
+) -> IntValue<'ctx> {
+    let block = env.builder.get_insert_block().expect("to be in a function");
+    let di_location = env.builder.get_current_debug_location().unwrap();
+
+    let symbol = Symbol::GENERIC_HASH;
+    let fn_name = layout_ids
+        .get(symbol, &layout)
+        .to_symbol_string(symbol, &env.interns);
+
+    let function = match env.module.get_function(fn_name.as_str()) {
+        Some(function_value) => function_value,
+        None => {
+            let arena = env.arena;
+
+            let seed_type = env.context.i64_type();
+
+            let arg_type = basic_type_from_layout(arena, env.context, &layout, env.ptr_bytes);
+
+            let function_value = crate::llvm::refcounting::build_header_help(
+                env,
+                &fn_name,
+                seed_type.into(),
+                &[seed_type.into(), arg_type],
+            );
+
+            build_hash_list_help(
+                env,
+                layout_ids,
+                function_value,
+                when_recursive,
+                element_layout,
+            );
+
+            function_value
+        }
+    };
+
+    env.builder.position_at_end(block);
+    env.builder
+        .set_current_debug_location(env.context, di_location);
+    let call = env
+        .builder
+        .build_call(function, &[seed.into(), value.into()], "struct_hash");
+
+    call.set_call_convention(FAST_CALL_CONV);
+
+    call.try_as_basic_value().left().unwrap().into_int_value()
+}
+
+fn build_hash_list_help<'a, 'ctx, 'env>(
+    env: &Env<'a, 'ctx, 'env>,
+    layout_ids: &mut LayoutIds<'a>,
+    parent: FunctionValue<'ctx>,
+    when_recursive: WhenRecursive<'a>,
+    element_layout: &Layout<'a>,
+) {
+    let ctx = env.context;
+    let builder = env.builder;
+
+    {
+        use inkwell::debug_info::AsDIScope;
+
+        let func_scope = parent.get_subprogram().unwrap();
+        let lexical_block = env.dibuilder.create_lexical_block(
+            /* scope */ func_scope.as_debug_info_scope(),
+            /* file */ env.compile_unit.get_file(),
+            /* line_no */ 0,
+            /* column_no */ 0,
+        );
+
+        let loc = env.dibuilder.create_debug_location(
+            ctx,
+            /* line */ 0,
+            /* column */ 0,
+            /* current_scope */ lexical_block.as_debug_info_scope(),
+            /* inlined_at */ None,
+        );
+        builder.set_current_debug_location(&ctx, loc);
+    }
+
+    // Add args to scope
+    let mut it = parent.get_param_iter();
+    let seed = it.next().unwrap().into_int_value();
+    let value = it.next().unwrap().into_struct_value();
+
+    set_name(seed.into(), Symbol::ARG_1.ident_string(&env.interns));
+    set_name(value.into(), Symbol::ARG_2.ident_string(&env.interns));
+
+    let entry = ctx.append_basic_block(parent, "entry");
+    env.builder.position_at_end(entry);
+
+    let result = hash_list(
+        env,
+        layout_ids,
+        parent,
+        seed,
+        value,
+        when_recursive,
+        element_layout,
+    );
+
+    env.builder.build_return(Some(&result));
+}
+
+fn hash_list<'a, 'ctx, 'env>(
+    env: &Env<'a, 'ctx, 'env>,
+    layout_ids: &mut LayoutIds<'a>,
+    parent: FunctionValue<'ctx>,
+    seed: IntValue<'ctx>,
+    value: StructValue<'ctx>,
+    when_recursive: WhenRecursive<'a>,
+    element_layout: &Layout<'a>,
+) -> IntValue<'ctx> {
+    use crate::llvm::build_list::{incrementing_elem_loop, load_list};
+    use inkwell::types::BasicType;
+
+    // hash of a list is the hash of its elements
+    let done_block = env.context.append_basic_block(parent, "done");
+    let loop_block = env.context.append_basic_block(parent, "loop");
+
+    let element_type =
+        basic_type_from_layout(env.arena, env.context, element_layout, env.ptr_bytes);
+    let ptr_type = element_type.ptr_type(inkwell::AddressSpace::Generic);
+
+    let (length, ptr) = load_list(env.builder, value, ptr_type);
+
+    let result = env.builder.build_alloca(env.context.i64_type(), "result");
+    env.builder.build_store(result, seed);
+
+    let is_empty = env.builder.build_int_compare(
+        inkwell::IntPredicate::EQ,
+        length,
+        env.ptr_int().const_zero(),
+        "is_empty",
+    );
+
+    env.builder
+        .build_conditional_branch(is_empty, done_block, loop_block);
+
+    env.builder.position_at_end(loop_block);
+
+    let loop_fn = |_index, element| {
+        let seed = env
+            .builder
+            .build_load(result, "load_current")
+            .into_int_value();
+
+        let answer = append_hash_layout(
+            env,
+            layout_ids,
+            seed,
+            element,
+            element_layout,
+            when_recursive.clone(),
+        );
+
+        env.builder.build_store(result, answer);
+    };
+
+    incrementing_elem_loop(
+        env.builder,
+        env.context,
+        parent,
+        ptr,
+        length,
+        "current_index",
+        loop_fn,
+    );
+
+    env.builder.build_unconditional_branch(done_block);
+
+    env.builder.position_at_end(done_block);
+
+    env.builder
+        .build_load(result, "load_current")
+        .into_int_value()
+}
+
+fn hash_null(seed: IntValue<'_>) -> IntValue<'_> {
+    seed
+}
+
+fn hash_empty_collection(seed: IntValue<'_>) -> IntValue<'_> {
+    seed
+}
+
+fn hash_ptr_to_struct<'a, 'ctx, 'env>(
+    env: &Env<'a, 'ctx, 'env>,
+    layout_ids: &mut LayoutIds<'a>,
+    union_layout: &UnionLayout<'a>,
+    field_layouts: &'a [Layout<'a>],
+    seed: IntValue<'ctx>,
+    tag: PointerValue<'ctx>,
+) -> IntValue<'ctx> {
+    use inkwell::types::BasicType;
+
+    let struct_layout = Layout::Struct(field_layouts);
+
+    let wrapper_type =
+        basic_type_from_layout(env.arena, env.context, &struct_layout, env.ptr_bytes);
+    debug_assert!(wrapper_type.is_struct_type());
+
+    // cast the opaque pointer to a pointer of the correct shape
+    let struct_ptr = env
+        .builder
+        .build_bitcast(
+            tag,
+            wrapper_type.ptr_type(inkwell::AddressSpace::Generic),
+            "opaque_to_correct",
+        )
+        .into_pointer_value();
+
+    let struct_value = env
+        .builder
+        .build_load(struct_ptr, "load_struct1")
+        .into_struct_value();
+
+    build_hash_struct(
+        env,
+        layout_ids,
+        field_layouts,
+        WhenRecursive::Loop(union_layout.clone()),
+        seed,
+        struct_value,
+    )
+}
+
+fn store_and_use_as_u8_ptr<'a, 'ctx, 'env>(
+    env: &Env<'a, 'ctx, 'env>,
+    value: BasicValueEnum<'ctx>,
+    layout: &Layout<'a>,
+) -> PointerValue<'ctx> {
+    let basic_type = basic_type_from_layout(env.arena, env.context, &layout, env.ptr_bytes);
+    let alloc = env.builder.build_alloca(basic_type, "store");
+    env.builder.build_store(alloc, value);
+
+    env.builder
+        .build_bitcast(
+            alloc,
+            env.context
+                .i8_type()
+                .ptr_type(inkwell::AddressSpace::Generic),
+            "as_u8_ptr",
+        )
+        .into_pointer_value()
+}
+
+fn hash_bitcode_fn<'a, 'ctx, 'env>(
+    env: &Env<'a, 'ctx, 'env>,
+    seed: IntValue<'ctx>,
+    buffer: PointerValue<'ctx>,
+    width: u32,
+) -> IntValue<'ctx> {
+    let num_bytes = env.context.i64_type().const_int(width as u64, false);
+
+    call_bitcode_fn(
+        env,
+        &[seed.into(), buffer.into(), num_bytes.into()],
+        &bitcode::DICT_HASH,
+    )
+    .into_int_value()
+}
+
+fn nonrec_tag_id<'a, 'ctx, 'env>(
+    env: &Env<'a, 'ctx, 'env>,
+    tag: StructValue<'ctx>,
+) -> IntValue<'ctx> {
+    complex_bitcast(
+        env.builder,
+        tag.into(),
+        env.context.i64_type().into(),
+        "load_tag_id",
+    )
+    .into_int_value()
+}
+
+unsafe fn rec_tag_id_unsafe<'a, 'ctx, 'env>(
+    env: &Env<'a, 'ctx, 'env>,
+    tag: PointerValue<'ctx>,
+) -> IntValue<'ctx> {
+    let ptr = env
+        .builder
+        .build_bitcast(
+            tag,
+            env.context
+                .i64_type()
+                .ptr_type(inkwell::AddressSpace::Generic),
+            "cast_for_tag_id",
+        )
+        .into_pointer_value();
+
+    env.builder.build_load(ptr, "load_tag_id").into_int_value()
+}

compiler/gen/src/llvm/build_list.rs

@@ -133,7 +133,7 @@ pub fn list_repeat<'a, 'ctx, 'env>(
     )
 }
 
-/// List.prepend List elem, elem -> List elem
+/// List.prepend : List elem, elem -> List elem
 pub fn list_prepend<'a, 'ctx, 'env>(
     env: &Env<'a, 'ctx, 'env>,
     inplace: InPlace,

compiler/gen/src/llvm/build_str.rs

@@ -3,8 +3,9 @@ use crate::llvm::build::{
 };
 use crate::llvm::build_list::{allocate_list, store_list};
 use crate::llvm::convert::collection;
+use inkwell::builder::Builder;
 use inkwell::types::BasicTypeEnum;
-use inkwell::values::{BasicValueEnum, IntValue, StructValue};
+use inkwell::values::{BasicValueEnum, IntValue, PointerValue, StructValue};
 use inkwell::AddressSpace;
 use roc_builtins::bitcode;
 use roc_module::symbol::Symbol;
@@ -68,7 +69,7 @@ fn str_symbol_to_i128<'a, 'ctx, 'env>(
     complex_bitcast(&env.builder, string, i128_type, "str_to_i128").into_int_value()
 }
 
-fn str_to_i128<'a, 'ctx, 'env>(
+pub fn str_to_i128<'a, 'ctx, 'env>(
     env: &Env<'a, 'ctx, 'env>,
     value: BasicValueEnum<'ctx>,
 ) -> IntValue<'ctx> {
@@ -125,6 +126,24 @@ fn zig_str_to_struct<'a, 'ctx, 'env>(
     builder.build_load(ptr4, "load").into_struct_value()
 }
 
+pub fn destructure<'ctx>(
+    builder: &Builder<'ctx>,
+    wrapper_struct: StructValue<'ctx>,
+) -> (PointerValue<'ctx>, IntValue<'ctx>) {
+    let length = builder
+        .build_extract_value(wrapper_struct, Builtin::WRAPPER_LEN, "list_len")
+        .unwrap()
+        .into_int_value();
+
+    // a `*mut u8` pointer
+    let generic_ptr = builder
+        .build_extract_value(wrapper_struct, Builtin::WRAPPER_PTR, "read_list_ptr")
+        .unwrap()
+        .into_pointer_value();
+
+    (generic_ptr, length)
+}
+
 /// Str.concat : Str, Str -> Str
 pub fn str_concat<'a, 'ctx, 'env>(
     env: &Env<'a, 'ctx, 'env>,

compiler/gen/src/llvm/convert.rs

@@ -185,7 +185,7 @@ pub fn basic_type_from_builtin<'ctx>(
         Float64 => context.f64_type().as_basic_type_enum(),
         Float32 => context.f32_type().as_basic_type_enum(),
         Float16 => context.f16_type().as_basic_type_enum(),
-        Dict(_, _) | EmptyDict => panic!("TODO layout_to_basic_type for Builtin::Dict"),
+        Dict(_, _) | EmptyDict => collection(context, ptr_bytes).into(),
         Set(_) | EmptySet => panic!("TODO layout_to_basic_type for Builtin::Set"),
         List(_, _) | Str | EmptyStr => collection(context, ptr_bytes).into(),
         EmptyList => BasicTypeEnum::StructType(collection(context, ptr_bytes)),

compiler/gen/src/llvm/mod.rs

@@ -1,4 +1,6 @@
 pub mod build;
+pub mod build_dict;
+pub mod build_hash;
 pub mod build_list;
 pub mod build_str;
 pub mod compare;

compiler/gen/tests/gen_dict.rs

@@ -0,0 +1,28 @@
+#[macro_use]
+extern crate pretty_assertions;
+#[macro_use]
+extern crate indoc;
+
+extern crate bumpalo;
+extern crate inkwell;
+extern crate libc;
+extern crate roc_gen;
+
+#[macro_use]
+mod helpers;
+
+#[cfg(test)]
+mod gen_dict {
+    #[test]
+    fn dict_empty_len() {
+        assert_evals_to!(
+            indoc!(
+                r#"
+                    Dict.len Dict.empty
+                "#
+            ),
+            0,
+            usize
+        );
+    }
+}

compiler/gen/tests/gen_hash.rs

@@ -0,0 +1,157 @@
+#[macro_use]
+extern crate pretty_assertions;
+#[macro_use]
+extern crate indoc;
+
+extern crate bumpalo;
+extern crate inkwell;
+extern crate libc;
+extern crate roc_gen;
+
+#[macro_use]
+mod helpers;
+
+#[cfg(test)]
+mod gen_hash {
+
+    #[test]
+    fn basic_hash() {
+        assert_evals_to!(
+            indoc!(
+                r#"
+                    Dict.hashTestOnly 0 0
+                "#
+            ),
+            9718519427346233646,
+            u64
+        );
+    }
+
+    #[test]
+    fn hash_str_with_seed() {
+        assert_evals_to!("Dict.hashTestOnly 1 \"a\"", 0xbed235177f41d328, u64);
+        assert_evals_to!("Dict.hashTestOnly 2 \"abc\"", 0xbe348debe59b27c3, u64);
+    }
+
+    #[test]
+    fn hash_record() {
+        assert_evals_to!("Dict.hashTestOnly 1 { x: \"a\" } ", 0xbed235177f41d328, u64);
+        assert_evals_to!(
+            "Dict.hashTestOnly 1 { x: 42, y: 3.14 } ",
+            5348189196103430707,
+            u64
+        );
+    }
+
+    #[test]
+    fn hash_result() {
+        assert_evals_to!(
+            "Dict.hashTestOnly 0 (List.get [ 0x1 ] 0) ",
+            2878521786781103245,
+            u64
+        );
+    }
+
+    #[test]
+    fn hash_linked_list() {
+        assert_evals_to!(
+            indoc!(
+                r#"
+                    LinkedList a : [ Nil, Cons a (LinkedList a) ]
+
+                    input : LinkedList I64
+                    input = Nil
+
+                    Dict.hashTestOnly 0 input 
+                "#
+            ),
+            0,
+            u64
+        );
+
+        assert_evals_to!(
+            indoc!(
+                r#"
+                    LinkedList a : [ Nil, Cons a (LinkedList a) ]
+
+                    input : LinkedList I64
+                    input = Cons 4 (Cons 3 Nil)
+
+                    Dict.hashTestOnly 0 input 
+                "#
+            ),
+            8287696503006938486,
+            u64
+        );
+    }
+
+    #[test]
+    fn hash_expr() {
+        assert_evals_to!(
+            indoc!(
+                r#"
+                    Expr : [ Add Expr Expr, Mul Expr Expr, Val I64, Var I64 ]
+
+                    x : Expr 
+                    x = Val 1
+
+                    Dict.hashTestOnly 0 (Add x x) 
+                "#
+            ),
+            18264046914072177411,
+            u64
+        );
+    }
+
+    #[test]
+    fn hash_nullable_expr() {
+        assert_evals_to!(
+            indoc!(
+                r#"
+                    Expr : [ Add Expr Expr, Mul Expr Expr, Val I64, Empty ]
+
+                    x : Expr 
+                    x = Val 1
+
+                    Dict.hashTestOnly 0 (Add x x) 
+                "#
+            ),
+            11103255846683455235,
+            u64
+        );
+    }
+
+    #[test]
+    fn hash_rosetree() {
+        assert_evals_to!(
+            indoc!(
+                r#"
+                Rose a : [ Rose (List (Rose a)) ]
+
+                x : Rose I64 
+                x = Rose [] 
+
+                Dict.hashTestOnly 0 x
+                "#
+            ),
+            0,
+            u64
+        );
+    }
+
+    #[test]
+    fn hash_list() {
+        assert_evals_to!(
+            indoc!(
+                r#"
+                x : List Str 
+                x = [ "foo", "bar", "baz" ] 
+
+                Dict.hashTestOnly 0 x
+                "#
+            ),
+            10731521034618280801,
+            u64
+        );
+    }
+}

compiler/gen/tests/helpers/eval.rs

@@ -1,7 +1,11 @@
 use libloading::Library;
 use roc_build::link::module_to_dylib;
 use roc_build::program::FunctionIterator;
+use roc_can::builtins::{builtin_defs_map, dict_hash_test_only};
+use roc_can::def::Def;
 use roc_collections::all::{MutMap, MutSet};
+use roc_module::symbol::Symbol;
+use roc_types::subs::VarStore;
 
 fn promote_expr_to_module(src: &str) -> String {
     let mut buffer = String::from("app \"test\" provides [ main ] to \"./platform\"\n\nmain =\n");
@@ -15,6 +19,15 @@ fn promote_expr_to_module(src: &str) -> String {
 
     buffer
 }
+pub fn test_builtin_defs(symbol: Symbol, var_store: &mut VarStore) -> Option<Def> {
+    match builtin_defs_map(symbol, var_store) {
+        Some(def) => Some(def),
+        None => match symbol {
+            Symbol::DICT_TEST_HASH => Some(dict_hash_test_only(symbol, var_store)),
+            _ => None,
+        },
+    }
+}
 
 pub fn helper<'a>(
     arena: &'a bumpalo::Bump,
@@ -53,6 +66,7 @@ pub fn helper<'a>(
         src_dir,
         exposed_types,
         ptr_bytes,
+        test_builtin_defs,
     );
 
     let mut loaded = loaded.expect("failed to load module");

compiler/gen_dev/tests/helpers/eval.rs

@@ -1,5 +1,6 @@
 use libloading::Library;
 use roc_build::link::{link, LinkType};
+use roc_can::builtins::builtin_defs_map;
 use roc_collections::all::MutMap;
 use tempfile::tempdir;
 
@@ -51,6 +52,7 @@ pub fn helper<'a>(
         src_dir,
         exposed_types,
         8,
+        builtin_defs_map,
     );
 
     let mut loaded = loaded.expect("failed to load module");

compiler/load/src/file.rs

@@ -6,7 +6,7 @@ use crossbeam::thread;
 use parking_lot::Mutex;
 use roc_builtins::std::{Mode, StdLib};
 use roc_can::constraint::Constraint;
-use roc_can::def::Declaration;
+use roc_can::def::{Declaration, Def};
 use roc_can::module::{canonicalize_module_defs, Module};
 use roc_collections::all::{default_hasher, MutMap, MutSet};
 use roc_constrain::module::{
@@ -1012,14 +1012,18 @@ fn enqueue_task<'a>(
     Ok(())
 }
 
-pub fn load_and_typecheck<'a>(
+pub fn load_and_typecheck<'a, F>(
     arena: &'a Bump,
     filename: PathBuf,
     stdlib: &'a StdLib,
     src_dir: &Path,
     exposed_types: SubsByModule,
     ptr_bytes: u32,
-) -> Result<LoadedModule, LoadingProblem<'a>> {
+    look_up_builtin: F,
+) -> Result<LoadedModule, LoadingProblem<'a>>
+where
+    F: Fn(Symbol, &mut VarStore) -> Option<Def> + 'static + Send + Copy,
+{
     use LoadResult::*;
 
     let load_start = LoadStart::from_path(arena, filename, stdlib.mode)?;
@@ -1032,20 +1036,25 @@ pub fn load_and_typecheck<'a>(
         exposed_types,
         Phase::SolveTypes,
         ptr_bytes,
+        look_up_builtin,
     )? {
         Monomorphized(_) => unreachable!(""),
         TypeChecked(module) => Ok(module),
     }
 }
 
-pub fn load_and_monomorphize<'a>(
+pub fn load_and_monomorphize<'a, F>(
     arena: &'a Bump,
     filename: PathBuf,
     stdlib: &'a StdLib,
     src_dir: &Path,
     exposed_types: SubsByModule,
     ptr_bytes: u32,
-) -> Result<MonomorphizedModule<'a>, LoadingProblem<'a>> {
+    look_up_builtin: F,
+) -> Result<MonomorphizedModule<'a>, LoadingProblem<'a>>
+where
+    F: Fn(Symbol, &mut VarStore) -> Option<Def> + 'static + Send + Copy,
+{
     use LoadResult::*;
 
     let load_start = LoadStart::from_path(arena, filename, stdlib.mode)?;
@@ -1058,13 +1067,15 @@ pub fn load_and_monomorphize<'a>(
         exposed_types,
         Phase::MakeSpecializations,
         ptr_bytes,
+        look_up_builtin,
     )? {
         Monomorphized(module) => Ok(module),
         TypeChecked(_) => unreachable!(""),
     }
 }
 
-pub fn load_and_monomorphize_from_str<'a>(
+#[allow(clippy::too_many_arguments)]
+pub fn load_and_monomorphize_from_str<'a, F>(
     arena: &'a Bump,
     filename: PathBuf,
     src: &'a str,
@@ -1072,7 +1083,11 @@ pub fn load_and_monomorphize_from_str<'a>(
     src_dir: &Path,
     exposed_types: SubsByModule,
     ptr_bytes: u32,
-) -> Result<MonomorphizedModule<'a>, LoadingProblem<'a>> {
+    look_up_builtin: F,
+) -> Result<MonomorphizedModule<'a>, LoadingProblem<'a>>
+where
+    F: Fn(Symbol, &mut VarStore) -> Option<Def> + 'static + Send + Copy,
+{
     use LoadResult::*;
 
     let load_start = LoadStart::from_str(arena, filename, src, stdlib.mode)?;
@@ -1085,6 +1100,7 @@ pub fn load_and_monomorphize_from_str<'a>(
         exposed_types,
         Phase::MakeSpecializations,
         ptr_bytes,
+        look_up_builtin,
     )? {
         Monomorphized(module) => Ok(module),
         TypeChecked(_) => unreachable!(""),
@@ -1213,7 +1229,8 @@ enum LoadResult<'a> {
 ///     and then linking them together, and possibly caching them by the hash of their
 ///     specializations, so if none of their specializations changed, we don't even need
 ///     to rebuild the module and can link in the cached one directly.)
-fn load<'a>(
+#[allow(clippy::too_many_arguments)]
+fn load<'a, F>(
     arena: &'a Bump,
     //filename: PathBuf,
     load_start: LoadStart<'a>,
@@ -1222,8 +1239,10 @@ fn load<'a>(
     exposed_types: SubsByModule,
     goal_phase: Phase,
     ptr_bytes: u32,
+    look_up_builtins: F,
 ) -> Result<LoadResult<'a>, LoadingProblem<'a>>
 where
+    F: Fn(Symbol, &mut VarStore) -> Option<Def> + 'static + Send + Copy,
 {
     let LoadStart {
         arc_modules,
@@ -1317,6 +1336,7 @@ where
                     .stack_size(EXPANDED_STACK_SIZE)
                     .spawn(move |_| {
                         // Keep listening until we receive a Shutdown msg
+
                         for msg in worker_msg_rx.iter() {
                             match msg {
                                 WorkerMsg::Shutdown => {
@@ -1343,6 +1363,7 @@ where
                                             src_dir,
                                             msg_tx.clone(),
                                             ptr_bytes,
+                                            look_up_builtins,
                                         );
 
                                         match result {
@@ -3362,7 +3383,8 @@ fn unpack_exposes_entries<'a>(
     output
 }
 
-fn canonicalize_and_constrain<'a>(
+#[allow(clippy::too_many_arguments)]
+fn canonicalize_and_constrain<'a, F>(
     arena: &'a Bump,
     module_ids: &ModuleIds,
     dep_idents: MutMap<ModuleId, IdentIds>,
@@ -3370,7 +3392,11 @@ fn canonicalize_and_constrain<'a>(
     aliases: MutMap<Symbol, Alias>,
     mode: Mode,
     parsed: ParsedModule<'a>,
-) -> Result<Msg<'a>, LoadingProblem<'a>> {
+    look_up_builtins: F,
+) -> Result<Msg<'a>, LoadingProblem<'a>>
+where
+    F: Fn(Symbol, &mut VarStore) -> Option<Def> + 'static + Send + Copy,
+{
     let canonicalize_start = SystemTime::now();
 
     let ParsedModule {
@@ -3408,6 +3434,7 @@ fn canonicalize_and_constrain<'a>(
         exposed_imports,
         &exposed_symbols,
         &mut var_store,
+        look_up_builtins,
     );
     let canonicalize_end = SystemTime::now();
 
@@ -3836,13 +3863,17 @@ fn add_def_to_module<'a>(
     }
 }
 
-fn run_task<'a>(
+fn run_task<'a, F>(
     task: BuildTask<'a>,
     arena: &'a Bump,
     src_dir: &Path,
     msg_tx: MsgSender<'a>,
     ptr_bytes: u32,
-) -> Result<(), LoadingProblem<'a>> {
+    look_up_builtins: F,
+) -> Result<(), LoadingProblem<'a>>
+where
+    F: Fn(Symbol, &mut VarStore) -> Option<Def> + 'static + Send + Copy,
+{
     use BuildTask::*;
 
     let msg = match task {
@@ -3878,6 +3909,7 @@ fn run_task<'a>(
             aliases,
             mode,
             parsed,
+            look_up_builtins,
         ),
         Solve {
             module,

compiler/load/tests/test_load.rs

@@ -18,6 +18,7 @@ mod test_load {
     use crate::helpers::fixtures_dir;
     use bumpalo::Bump;
     use inlinable_string::InlinableString;
+    use roc_can::builtins::builtin_defs_map;
     use roc_can::def::Declaration::*;
     use roc_can::def::Def;
     use roc_collections::all::MutMap;
@@ -86,6 +87,7 @@ mod test_load {
                     dir.path(),
                     exposed_types,
                     8,
+                    builtin_defs_map,
                 )
             };
 
@@ -128,6 +130,7 @@ mod test_load {
             src_dir.as_path(),
             subs_by_module,
             8,
+            builtin_defs_map,
         );
         let mut loaded_module = loaded.expect("Test module failed to load");
 
@@ -291,6 +294,7 @@ mod test_load {
             src_dir.as_path(),
             subs_by_module,
             8,
+            builtin_defs_map,
         );
 
         let mut loaded_module = loaded.expect("Test module failed to load");

compiler/module/src/low_level.rs

@@ -28,6 +28,9 @@ pub enum LowLevel {
     ListWalk,
     ListWalkBackwards,
     ListSum,
+    DictSize,
+    DictEmpty,
+    DictInsert,
     NumAdd,
     NumAddWrap,
     NumAddChecked,
@@ -66,4 +69,5 @@ pub enum LowLevel {
     And,
     Or,
     Not,
+    Hash,
 }

compiler/module/src/symbol.rs

@@ -742,6 +742,7 @@ define_builtins! {
         12 ARG_CLOSURE: "#arg_closure" // symbol used to store the closure record
         13 LIST_EQ: "#list_eq" // internal function that checks list equality
         14 GENERIC_EQ: "#generic_eq" // internal function that checks generic equality
+        15 GENERIC_HASH: "#generic_hash" // internal function that checks list equality
     }
     1 NUM: "Num" => {
         0 NUM_NUM: "Num" imported // the Num.Num type alias
@@ -893,6 +894,11 @@ define_builtins! {
         3 DICT_SINGLETON: "singleton"
         4 DICT_GET: "get"
         5 DICT_INSERT: "insert"
+        6 DICT_LEN: "len"
+
+        // This should not be exposed to users, its for testing the
+        // hash function ONLY
+        7 DICT_TEST_HASH: "hashTestOnly"
     }
     7 SET: "Set" => {
         0 SET_SET: "Set" imported // the Set.Set type alias

compiler/mono/src/borrow.rs

@@ -588,5 +588,9 @@ pub fn lowlevel_borrow_signature(arena: &Bump, op: LowLevel) -> &[bool] {
         }
         StrStartsWith | StrEndsWith => arena.alloc_slice_copy(&[owned, borrowed]),
         StrFromInt => arena.alloc_slice_copy(&[irrelevant]),
+        Hash => arena.alloc_slice_copy(&[borrowed, irrelevant]),
+        DictSize => arena.alloc_slice_copy(&[borrowed]),
+        DictEmpty => &[],
+        DictInsert => arena.alloc_slice_copy(&[owned, owned, owned]),
     }
 }

compiler/mono/src/layout.rs

@@ -392,7 +392,6 @@ impl<'a> Layout<'a> {
         content: Content,
     ) -> Result<Self, LayoutProblem> {
         use roc_types::subs::Content::*;
-
         match content {
             FlexVar(_) | RigidVar(_) => Err(LayoutProblem::UnresolvedTypeVar(var)),
             RecursionVar { structure, .. } => {
@@ -961,6 +960,7 @@ fn layout_from_flat_type<'a>(
 
                 Symbol::STR_STR => Ok(Layout::Builtin(Builtin::Str)),
                 Symbol::LIST_LIST => list_layout_from_elem(env, args[0]),
+                Symbol::DICT_DICT => dict_layout_from_key_value(env, args[0], args[1]),
                 Symbol::ATTR_ATTR => {
                     debug_assert_eq!(args.len(), 2);
 
@@ -1796,6 +1796,47 @@ fn unwrap_num_tag<'a>(subs: &Subs, var: Variable) -> Result<Layout<'a>, LayoutPr
     }
 }
 
+fn dict_layout_from_key_value<'a>(
+    env: &mut Env<'a, '_>,
+    key_var: Variable,
+    value_var: Variable,
+) -> Result<Layout<'a>, LayoutProblem> {
+    match env.subs.get_without_compacting(key_var).content {
+        Content::Structure(FlatType::Apply(Symbol::ATTR_ATTR, key_args)) => {
+            debug_assert_eq!(key_args.len(), 2);
+
+            let var = *key_args.get(1).unwrap();
+
+            dict_layout_from_key_value(env, var, value_var)
+        }
+        Content::FlexVar(_) | Content::RigidVar(_) => {
+            // If this was still a (Dict * *) then it must have been an empty dict
+            Ok(Layout::Builtin(Builtin::EmptyDict))
+        }
+        key_content => {
+            match env.subs.get_without_compacting(value_var).content {
+                Content::Structure(FlatType::Apply(Symbol::ATTR_ATTR, value_args)) => {
+                    debug_assert_eq!(value_args.len(), 2);
+
+                    let var = *value_args.get(1).unwrap();
+
+                    dict_layout_from_key_value(env, key_var, var)
+                }
+                value_content => {
+                    let key_layout = Layout::new_help(env, key_var, key_content)?;
+                    let value_layout = Layout::new_help(env, value_var, value_content)?;
+
+                    // This is a normal list.
+                    Ok(Layout::Builtin(Builtin::Dict(
+                        env.arena.alloc(key_layout),
+                        env.arena.alloc(value_layout),
+                    )))
+                }
+            }
+        }
+    }
+}
+
 pub fn list_layout_from_elem<'a>(
     env: &mut Env<'a, '_>,
     elem_var: Variable,

compiler/mono/tests/test_mono.rs

@@ -12,6 +12,7 @@ mod helpers;
 // Test monomorphization
 #[cfg(test)]
 mod test_mono {
+    use roc_can::builtins::builtin_defs_map;
     use roc_collections::all::MutMap;
     use roc_module::symbol::Symbol;
     use roc_mono::ir::Proc;
@@ -54,6 +55,7 @@ mod test_mono {
         }
 
         let exposed_types = MutMap::default();
+
         let loaded = roc_load::file::load_and_monomorphize_from_str(
             arena,
             filename,
@@ -62,6 +64,7 @@ mod test_mono {
             src_dir,
             exposed_types,
             8,
+            builtin_defs_map,
         );
 
         let mut loaded = loaded.expect("failed to load module");
@@ -631,6 +634,31 @@ mod test_mono {
         )
     }
 
+    #[test]
+    fn dict() {
+        compiles_to_ir(
+            r#"
+            Dict.len Dict.empty
+            "#,
+            indoc!(
+                r#"
+                procedure Dict.2 ():
+                    let Test.4 = lowlevel DictEmpty ;
+                    ret Test.4;
+
+                procedure Dict.6 (#Attr.2):
+                    let Test.3 = lowlevel DictSize #Attr.2;
+                    ret Test.3;
+
+                procedure Test.0 ():
+                    let Test.2 = FunctionPointer Dict.2;
+                    let Test.1 = CallByName Dict.6 Test.2;
+                    ret Test.1;
+                "#
+            ),
+        )
+    }
+
     #[test]
     fn list_append_closure() {
         compiles_to_ir(

compiler/solve/tests/solve_expr.rs

@@ -10,6 +10,7 @@ mod helpers;
 #[cfg(test)]
 mod solve_expr {
     use crate::helpers::with_larger_debug_stack;
+    use roc_can::builtins::builtin_defs_map;
     use roc_collections::all::MutMap;
     use roc_types::pretty_print::{content_to_string, name_all_type_vars};
 
@@ -63,6 +64,7 @@ mod solve_expr {
                 dir.path(),
                 exposed_types,
                 8,
+                builtin_defs_map,
             );
 
             dir.close()?;

compiler/types/src/builtin_aliases.rs

@@ -377,6 +377,18 @@ fn nat_alias_content() -> SolvedType {
     int_alias_content(natural_type())
 }
 
+// U64
+
+#[inline(always)]
+pub fn u64_type() -> SolvedType {
+    SolvedType::Alias(Symbol::NUM_U64, vec![], Box::new(u64_alias_content()))
+}
+
+#[inline(always)]
+fn u64_alias_content() -> SolvedType {
+    int_alias_content(unsigned64_type())
+}
+
 // INT
 
 #[inline(always)]

docs/Cargo.toml

@@ -15,6 +15,7 @@ fs_extra = "1.2.0"
 pulldown-cmark = { version = "0.8", default-features = false }
 roc_load = { path = "../compiler/load" }
 roc_builtins = { path = "../compiler/builtins" }
+roc_can = { path = "../compiler/can" }
 roc_collections = { path = "../compiler/collections" }
 bumpalo = { version = "3.2", features = ["collections"] }
 

docs/src/main.rs

@@ -6,6 +6,7 @@ extern crate serde_derive;
 extern crate pulldown_cmark;
 extern crate serde_json;
 use roc_builtins::std::StdLib;
+use roc_can::builtins::builtin_defs_map;
 use roc_load::docs::Documentation;
 use roc_load::docs::ModuleDocumentation;
 
@@ -133,6 +134,7 @@ fn files_to_documentations(
             src_dir,
             MutMap::default(),
             8, // TODO: Is it okay to hardcode ptr_bytes here? I think it should be fine since we'er only type checking (also, 8 => 32bit system)
+            builtin_defs_map,
         )
         .expect("TODO gracefully handle load failing");
         files_docs.extend(loaded.documentation.drain().map(|x| x.1));

editor/src/keyboard_input.rs

@@ -1,6 +1,6 @@
 use crate::error::EdResult;
 use crate::mvc::app_model::AppModel;
-use crate::mvc::app_update::{handle_copy, handle_paste, pass_keydown_to_focused};
+use crate::mvc::app_update::{handle_copy, handle_cut, handle_paste, pass_keydown_to_focused};
 use winit::event::VirtualKeyCode::*;
 use winit::event::{ElementState, ModifiersState, VirtualKeyCode};
 
@@ -22,11 +22,7 @@ pub fn handle_keydown(
 
         Copy => handle_copy(app_model)?,
         Paste => handle_paste(app_model)?,
-        Cut => {
+        Cut => handle_cut(app_model)?,
-            //handle_cut(app_model)?
-            todo!("cut");
-        }
-
         C => {
             if modifiers.ctrl() {
                 handle_copy(app_model)?
@@ -39,8 +35,7 @@ pub fn handle_keydown(
         }
         X => {
             if modifiers.ctrl() {
-                //handle_cut(app_model)?
+                handle_cut(app_model)?
-                todo!("cut");
             }
         }
         _ => (),

editor/src/mvc/app_update.rs

@@ -8,7 +8,7 @@ use winit::event::{ModifiersState, VirtualKeyCode};
 pub fn handle_copy(app_model: &mut AppModel) -> EdResult<()> {
     if let Some(ref mut ed_model) = app_model.ed_model_opt {
         if ed_model.has_focus {
-            let selected_str_opt = super::ed_model::get_selected_str(ed_model)?;
+            let selected_str_opt = ed_model.get_selected_str()?;
 
             if let Some(selected_str) = selected_str_opt {
                 app_model::set_clipboard_txt(&mut app_model.clipboard_opt, selected_str)?;
@@ -76,6 +76,22 @@ pub fn handle_paste(app_model: &mut AppModel) -> EdResult<()> {
     Ok(())
 }
 
+pub fn handle_cut(app_model: &mut AppModel) -> EdResult<()> {
+    if let Some(ref mut ed_model) = app_model.ed_model_opt {
+        if ed_model.has_focus {
+            let selected_str_opt = ed_model.get_selected_str()?;
+
+            if let Some(selected_str) = selected_str_opt {
+                app_model::set_clipboard_txt(&mut app_model.clipboard_opt, selected_str)?;
+
+                ed_model.del_selection()?;
+            }
+        }
+    }
+
+    Ok(())
+}
+
 pub fn pass_keydown_to_focused(
     modifiers: &ModifiersState,
     virtual_keycode: VirtualKeyCode,
@@ -102,7 +118,7 @@ pub fn handle_new_char(received_char: &char, app_model: &mut AppModel) -> EdResu
 pub mod test_app_update {
     use crate::mvc::app_model;
     use crate::mvc::app_model::{AppModel, Clipboard};
-    use crate::mvc::app_update::{handle_copy, handle_paste};
+    use crate::mvc::app_update::{handle_copy, handle_cut, handle_paste};
     use crate::mvc::ed_model::{EdModel, Position, RawSelection};
     use crate::mvc::ed_update::test_ed_update::gen_caret_text_buf;
     use crate::selection::test_selection::{all_lines_vec, convert_selection_to_dsl};
@@ -171,12 +187,42 @@ pub mod test_app_update {
         Ok(app_model.clipboard_opt)
     }
 
+    fn assert_cut(
+        pre_lines_str: &[&str],
+        expected_clipboard_content: &str,
+        expected_post_lines_str: &[&str],
+        clipboard_opt: Option<Clipboard>,
+    ) -> Result<Option<Clipboard>, String> {
+        let (caret_pos, selection_opt, pre_text_buf) = gen_caret_text_buf(pre_lines_str)?;
+
+        let mut app_model = mock_app_model(pre_text_buf, caret_pos, selection_opt, clipboard_opt);
+
+        handle_cut(&mut app_model)?;
+
+        let clipboard_content = app_model::get_clipboard_txt(&mut app_model.clipboard_opt)?;
+
+        assert_eq!(clipboard_content, expected_clipboard_content);
+
+        let ed_model = app_model.ed_model_opt.unwrap();
+        let mut text_buf_lines = all_lines_vec(&ed_model.text_buf);
+        let post_lines_str = convert_selection_to_dsl(
+            ed_model.selection_opt,
+            ed_model.caret_pos,
+            &mut text_buf_lines,
+        )?;
+
+        assert_eq!(post_lines_str, expected_post_lines_str);
+
+        Ok(app_model.clipboard_opt)
+    }
+
     #[test]
     #[ignore] // ignored because of clipboard problems on ci
-    fn copy_paste() -> Result<(), String> {
+    fn copy_paste_cut() -> Result<(), String> {
         // can only init clipboard once
         let mut clipboard_opt = AppModel::init_clipboard_opt();
 
+        // copy
         clipboard_opt = assert_copy(&["[a]|"], "a", clipboard_opt)?;
         clipboard_opt = assert_copy(&["|[b]"], "b", clipboard_opt)?;
         clipboard_opt = assert_copy(&["a[ ]|"], " ", clipboard_opt)?;
@@ -188,6 +234,8 @@ pub mod test_app_update {
             "ef\nghi",
             clipboard_opt,
         )?;
+
+        // paste
         clipboard_opt = assert_paste(&["|"], "", &["|"], clipboard_opt)?;
         clipboard_opt = assert_paste(&["|"], "a", &["a|"], clipboard_opt)?;
         clipboard_opt = assert_paste(&["a|"], "b", &["ab|"], clipboard_opt)?;
@@ -196,13 +244,27 @@ pub mod test_app_update {
         clipboard_opt = assert_paste(&["[ab]|"], "d", &["d|"], clipboard_opt)?;
         clipboard_opt = assert_paste(&["a[b]|c"], "e", &["ae|c"], clipboard_opt)?;
         clipboard_opt = assert_paste(&["a\n", "[b\n", "]|"], "f", &["a\n", "f|"], clipboard_opt)?;
-        assert_paste(
+        clipboard_opt = assert_paste(
             &["abc\n", "d[ef\n", "ghi]|\n", "jkl"],
             "ef\nghi",
             &["abc\n", "def\n", "ghi|\n", "jkl"],
             clipboard_opt,
         )?;
 
+        // cut
+        clipboard_opt = assert_cut(&["[a]|"], "a", &["|"], clipboard_opt)?;
+        clipboard_opt = assert_cut(&["|[b]"], "b", &["|"], clipboard_opt)?;
+        clipboard_opt = assert_cut(&["a[ ]|"], " ", &["a|"], clipboard_opt)?;
+        clipboard_opt = assert_cut(&["[ ]|b"], " ", &["|b"], clipboard_opt)?;
+        clipboard_opt = assert_cut(&["a\n", "[b\n", "]|"], "b\n", &["a\n", "|"], clipboard_opt)?;
+        clipboard_opt = assert_cut(&["[a\n", " b\n", "]|"], "a\n b\n", &["|"], clipboard_opt)?;
+        assert_cut(
+            &["abc\n", "d[ef\n", "ghi]|\n", "jkl"],
+            "ef\nghi",
+            &["abc\n", "d|\n", "jkl"],
+            clipboard_opt,
+        )?;
+
         Ok(())
     }
 }

editor/src/mvc/ed_model.rs

@@ -25,9 +25,10 @@ pub fn init_model(file_path: &Path) -> EdResult<EdModel> {
     })
 }
 
-pub fn get_selected_str(ed_model: &EdModel) -> EdResult<Option<&str>> {
+impl EdModel {
-    if let Some(curr_selection) = ed_model.selection_opt {
+    pub fn get_selected_str(&self) -> EdResult<Option<&str>> {
-        let selected_str = ed_model.text_buf.get_selection(curr_selection)?;
+        if let Some(curr_selection) = self.selection_opt {
+            let selected_str = self.text_buf.get_selection(curr_selection)?;
 
             Ok(Some(selected_str))
         } else {
@@ -35,6 +36,18 @@ pub fn get_selected_str(ed_model: &EdModel) -> EdResult<Option<&str>> {
         }
     }
 
+    pub fn del_selection(&mut self) -> EdResult<()> {
+        if let Some(selection) = self.selection_opt {
+            self.text_buf.del_selection(selection)?;
+
+            self.caret_pos = selection.start_pos;
+        }
+        self.selection_opt = None;
+
+        Ok(())
+    }
+}
+
 #[derive(Debug, Copy, Clone)]
 pub struct Position {
     pub line: usize,

editor/src/mvc/ed_update.rs

@@ -353,7 +353,7 @@ pub fn handle_new_char(received_char: &char, ed_model: &mut EdModel) -> EdResult
         }
         '\u{3}' // Ctrl + C
         | '\u{16}' // Ctrl + V
-        | '\u{30}' // Ctrl + X
+        | '\u{18}' // Ctrl + X
         | '\u{e000}'..='\u{f8ff}' // http://www.unicode.org/faq/private_use.html
         | '\u{f0000}'..='\u{ffffd}' // ^
         | '\u{100000}'..='\u{10fffd}' // ^