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Parse and reject "typescript-style" anonymous enums #100741

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estebank opened this issue Aug 19, 2022 · 4 comments
Open

Parse and reject "typescript-style" anonymous enums #100741

estebank opened this issue Aug 19, 2022 · 4 comments
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@LYF1999
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A-diagnostics Area: Messages for errors, warnings, and lints A-parser Area: The parsing of Rust source code to an AST. D-newcomer-roadblock Diagnostics: Confusing error or lint; hard to understand for new users. D-papercut Diagnostics: An error or lint that needs small tweaks. D-terse Diagnostics: An error or lint that doesn't give enough information about the problem at hand. P-low Low priority T-compiler Relevant to the compiler team, which will review and decide on the PR/issue.

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@estebank
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estebank commented Aug 19, 2022 •
edited by rustbot

Given

fn foo() -> i32 | &str { 42 }

we currently point at the | and complain about it not being expected.

Ideally, this should parse and explicitly state that anonymous enums are not supported, and provide a structured suggestion for

enum Name<'a> {
    VariantI32(i32),
    VariantStr(&'a str),
}
fn foo() -> Name<'_> {
    Name::VariantI32(42)
}

At least, we should emit a note suggesting the above in text without a structured suggestion (which will be easier to produce).
@estebank estebank added A-diagnostics Area: Messages for errors, warnings, and lints A-parser Area: The parsing of Rust source code to an AST. P-low Low priority T-compiler Relevant to the compiler team, which will review and decide on the PR/issue. D-papercut Diagnostics: An error or lint that needs small tweaks. D-newcomer-roadblock Diagnostics: Confusing error or lint; hard to understand for new users. D-terse Diagnostics: An error or lint that doesn't give enough information about the problem at hand. labels Aug 19, 2022
@LYF1999
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LYF1999 commented Aug 19, 2022

@rustbot claim

@LYF1999 LYF1999 mentioned this issue Aug 25, 2022
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@estebank estebank mentioned this issue Jan 17, 2023
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matthiaskrgr added a commit to matthiaskrgr/rust that referenced this issue Jan 23, 2023
@matthiaskrgr
Rollup merge of rust-lang#106960 - estebank:parse-anon-enums, r=cjgillot
ffd5181 
Teach parser to understand fake anonymous enum syntax

Parse `Ty | OtherTy` in function argument and return types.
Parse type ascription in top level patterns.

Minimally address rust-lang#100741.
matthiaskrgr added a commit to matthiaskrgr/rust that referenced this issue Jan 25, 2023
@matthiaskrgr
Rollup merge of rust-lang#106960 - estebank:parse-anon-enums, r=cjgillot
ce52f5d 
Teach parser to understand fake anonymous enum syntax

Parse `Ty | OtherTy` in function argument and return types.
Parse type ascription in top level patterns.

Minimally address rust-lang#100741.
matthiaskrgr added a commit to matthiaskrgr/rust that referenced this issue Jan 26, 2023
@matthiaskrgr
Rollup merge of rust-lang#106960 - estebank:parse-anon-enums, r=cjgillot
ba928ba 
Teach parser to understand fake anonymous enum syntax

Parse `Ty | OtherTy` in function argument and return types.
Parse type ascription in top level patterns.

Minimally address rust-lang#100741.
@nicopap nicopap mentioned this issue Jan 30, 2023
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@Nilstrieb
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Note: this had to be reverted because of the ambiguities. A new implementation has to be careful to only recover once invalid syntax has been discovered and not recover on the happy path.

@estebank
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To expand on the above: types can syntactically go in the same place closure and or binop expressions can, and macros that use | today need to continue working. Effectively, the new type parsing should be limited exclusively to type parameters, return types and maybe let binding types.

calebcartwright pushed a commit to calebcartwright/rust that referenced this issue Jun 20, 2023
@matthiaskrgr
Rollup merge of rust-lang#106960 - estebank:parse-anon-enums, r=cjgillot
1d9afb2 
Teach parser to understand fake anonymous enum syntax

Parse `Ty | OtherTy` in function argument and return types.
Parse type ascription in top level patterns.

Minimally address rust-lang#100741.
@Phosphorus-M
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Phosphorus-M commented Jun 30, 2023 •
edited

I love the idea! It's related to this RFC right?

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@LYF1999 LYF1999

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A-diagnostics Area: Messages for errors, warnings, and lints A-parser Area: The parsing of Rust source code to an AST. D-newcomer-roadblock Diagnostics: Confusing error or lint; hard to understand for new users. D-papercut Diagnostics: An error or lint that needs small tweaks. D-terse Diagnostics: An error or lint that doesn't give enough information about the problem at hand. P-low Low priority T-compiler Relevant to the compiler team, which will review and decide on the PR/issue.
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give some suggestion for returning anonymous enum LYF1999/rust
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@estebank @LYF1999 @Phosphorus-M @Nilstrieb