repl: get Str working properly in CLI and Wasm REPLs

Cargo.lock

@@ -3713,6 +3713,7 @@ dependencies = [
  "roc_mono",
  "roc_parse",
  "roc_repl_eval",
+ "roc_std",
  "roc_target",
  "roc_types",
  "rustyline",

repl_cli/Cargo.toml

@@ -24,15 +24,16 @@ target-lexicon = "0.12.2"
 
 # TODO: make llvm optional
 roc_build = {path = "../compiler/build", features = ["llvm"]}
+roc_builtins = {path = "../compiler/builtins"}
 roc_collections = {path = "../compiler/collections"}
 roc_gen_llvm = {path = "../compiler/gen_llvm"}
 roc_load = {path = "../compiler/load"}
 roc_mono = {path = "../compiler/mono"}
 roc_parse = {path = "../compiler/parse"}
 roc_repl_eval = {path = "../repl_eval"}
+roc_std = {path = "../roc_std"}
 roc_target = {path = "../compiler/roc_target"}
 roc_types = {path = "../compiler/types"}
-roc_builtins = {path = "../compiler/builtins"}
 
 [lib]
 name = "roc_repl_cli"

repl_cli/src/lib.rs

@@ -20,6 +20,7 @@ use roc_parse::parser::{EExpr, ELambda, SyntaxError};
 use roc_repl_eval::eval::jit_to_ast;
 use roc_repl_eval::gen::{compile_to_mono, format_answer, ReplOutput};
 use roc_repl_eval::{ReplApp, ReplAppMemory};
+use roc_std::RocStr;
 use roc_target::TargetInfo;
 use roc_types::pretty_print::{content_to_string, name_all_type_vars};
 
@@ -183,7 +184,8 @@ impl ReplAppMemory for CliMemory {
     deref_number!(deref_f64, f64);
 
     fn deref_str(&self, addr: usize) -> &str {
-        unsafe { *(addr as *const &'static str) }
+        let reference: &RocStr = unsafe { std::mem::transmute(addr) };
+        reference.as_str()
     }
 }
 

repl_eval/src/eval.rs

@@ -318,10 +318,16 @@ fn jit_to_ast_help<'a, A: ReplApp<'a>>(
 
             Ok(result)
         }
-        Layout::Builtin(Builtin::Str) => Ok(app
-            .call_function(main_fn_name, |_, string: &'static str| {
-                str_to_ast(env.arena, env.arena.alloc(string))
-            })),
+        Layout::Builtin(Builtin::Str) => {
+            let size = layout.stack_size(env.target_info) as usize;
+            Ok(
+                app.call_function_dynamic_size(main_fn_name, size, |mem: &A::Memory, addr| {
+                    let string = mem.deref_str(addr);
+                    let arena_str = env.arena.alloc_str(string);
+                    Expr::Str(StrLiteral::PlainLine(arena_str))
+                }),
+            )
+        }
         Layout::Builtin(Builtin::List(elem_layout)) => Ok(app.call_function(
             main_fn_name,
             |mem: &A::Memory, (addr, len): (usize, usize)| {
@@ -512,9 +518,9 @@ fn addr_to_ast<'a, M: ReplAppMemory>(
             list_to_ast(env, mem, elem_addr, len, elem_layout, content)
         }
         (_, Layout::Builtin(Builtin::Str)) => {
-            let arena_str = mem.deref_str(addr);
-
-            str_to_ast(env.arena, arena_str)
+            let string = mem.deref_str(addr);
+            let arena_str = env.arena.alloc_str(string);
+            Expr::Str(StrLiteral::PlainLine(arena_str))
         }
         (_, Layout::Struct{field_layouts, ..}) => match content {
             Content::Structure(FlatType::Record(fields, _)) => {
@@ -1214,41 +1220,3 @@ fn num_to_ast<'a>(env: &Env<'a, '_>, num_expr: Expr<'a>, content: &Content) -> E
 fn number_literal_to_ast<T: std::fmt::Display>(arena: &Bump, num: T) -> Expr<'_> {
     Expr::Num(arena.alloc(format!("{}", num)))
 }
-
-#[cfg(target_endian = "little")]
-/// NOTE: As of this writing, we don't have big-endian small strings implemented yet!
-fn str_to_ast<'a>(arena: &'a Bump, string: &'a str) -> Expr<'a> {
-    const STR_SIZE: usize = 2 * std::mem::size_of::<usize>();
-
-    let bytes: [u8; STR_SIZE] = unsafe { std::mem::transmute(string) };
-    let is_small = (bytes[STR_SIZE - 1] & 0b1000_0000) != 0;
-
-    if is_small {
-        let len = (bytes[STR_SIZE - 1] & 0b0111_1111) as usize;
-        let mut string = bumpalo::collections::String::with_capacity_in(len, arena);
-
-        for byte in bytes.iter().take(len) {
-            string.push(*byte as char);
-        }
-
-        str_slice_to_ast(arena, arena.alloc(string))
-    } else {
-        // Roc string literals are stored inside the constant section of the program
-        // That means this memory is gone when the jit function is done
-        // (as opposed to heap memory, which we can leak and then still use after)
-        // therefore we must make an owned copy of the string here
-        let string = bumpalo::collections::String::from_str_in(string, arena).into_bump_str();
-        str_slice_to_ast(arena, string)
-    }
-}
-
-fn str_slice_to_ast<'a>(_arena: &'a Bump, string: &'a str) -> Expr<'a> {
-    if string.contains('\n') {
-        todo!(
-            "this string contains newlines, so render it as a multiline string: {:?}",
-            Expr::Str(StrLiteral::PlainLine(string))
-        );
-    } else {
-        Expr::Str(StrLiteral::PlainLine(string))
-    }
-}

repl_test/src/tests.rs

@@ -221,19 +221,16 @@ fn literal_empty_str() {
     expect_success("\"\"", "\"\" : Str");
 }
 
-#[cfg(not(feature = "wasm"))]
 #[test]
 fn literal_ascii_str() {
     expect_success("\"Hello, World!\"", "\"Hello, World!\" : Str");
 }
 
-#[cfg(not(feature = "wasm"))]
 #[test]
 fn literal_utf8_str() {
     expect_success("\"👩‍👩‍👦‍👦\"", "\"👩‍👩‍👦‍👦\" : Str");
 }
 
-#[cfg(not(feature = "wasm"))]
 #[test]
 fn str_concat() {
     expect_success(

repl_test/src/wasm.rs

@@ -254,6 +254,7 @@ pub fn expect_success(input: &'static str, expected: &str) {
     assert_eq!(output, expected);
 }
 
+#[allow(dead_code)]
 pub fn expect_failure(input: &'static str, expected: &str) {
     let (ok, output) = run(input);
     assert_eq!(ok, false);

repl_wasm/src/repl.rs

@@ -64,10 +64,22 @@ impl<'a> ReplAppMemory for WasmMemory<'a> {
     deref_number!(deref_f64, f64);
 
     fn deref_str(&self, addr: usize) -> &str {
-        let elems_addr = self.deref_usize(addr);
-        let len = self.deref_usize(addr + size_of::<usize>());
-        let bytes = &self.copied_bytes[elems_addr..][..len];
-        std::str::from_utf8(bytes).unwrap()
+        // We can't use RocStr, we need our own small/big string logic.
+        // The first field is *not* a pointer. We can calculate a pointer for it, but only for big strings.
+        // If changing this code, remember it also runs in wasm32, not just the app.
+        let last_byte = self.copied_bytes[addr + 7] as i8;
+        let is_small = last_byte < 0;
+
+        let str_bytes = if is_small {
+            let len = (last_byte & 0x7f) as usize;
+            &self.copied_bytes[addr..][..len]
+        } else {
+            let chars_index = self.deref_usize(addr);
+            let len = self.deref_usize(addr + 4);
+            &self.copied_bytes[chars_index..][..len]
+        };
+
+        unsafe { std::str::from_utf8_unchecked(str_bytes) }
     }
 }