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Handle async qualifier inside trait #2779

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Dec 27, 2023
Merged

Handle async qualifier inside trait #2779

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eb15fb6
Handle `async` qualifier inside trait
braw-lee Dec 15, 2023
e97a817
Generate error for `async` trait fucntions
braw-lee Dec 16, 2023
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5 changes: 5 additions & 0 deletions gcc/rust/checks/errors/rust-ast-validation.cc
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Original file line number Diff line number Diff line change
Expand Up @@ -107,6 +107,11 @@ ASTValidation::visit (AST::Function &function)
rust_error_at (function.get_locus (), ErrorCode::E0379,
"functions in traits cannot be declared const");

// may change soon
if (qualifiers.is_async () && context.back () == Context::TRAIT_IMPL)
rust_error_at (function.get_locus (), ErrorCode::E0706,
"functions in traits cannot be declared %<async%>");
Comment on lines +110 to +113
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this is great :)


if (valid_context.find (context.back ()) == valid_context.end ()
&& function.has_self_param ())
rust_error_at (
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2 changes: 2 additions & 0 deletions gcc/rust/parse/rust-parse-impl.h
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Expand Up @@ -5784,6 +5784,8 @@ Parser<ManagedTokenSource>::parse_trait_impl_item ()
// function or method
return parse_trait_impl_function_or_method (visibility,
std::move (outer_attrs));
case ASYNC:
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const is handled this way because inside a trait, you could have a const variable or a constant function:

impl Foo for u32 {
    const TRAIT_ASSOC_CST: u32 = 15;
    
    const fn constant_fn() -> u32 { 14 }
}

for async, we can only have async functions - so we don't need to bundle the cases for CONST and ASYNC together.

Instead, this is what I would like to see:

Suggested change
case ASYNC:
case ASYNC:
return parse_async_item (visibility, std::move(outer_attrs))
case CONST:
/* snip */

return parse_async_item (visibility, std::move (outer_attrs));
case CONST:
// lookahead to resolve production - could be function/method or const
// item
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13 changes: 13 additions & 0 deletions gcc/testsuite/rust/compile/issue-2767.rs
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Original file line number Diff line number Diff line change
@@ -0,0 +1,13 @@
// { dg-additional-options "-frust-edition=2018" }
trait Foo {
fn f() -> u32;
}

impl Foo for u32 {
async fn f() -> u32 {
// { dg-error "functions in traits cannot be declared .async." "" { target *-*-* } .-1 }
22
}
}

fn main() {}