parse: unify function front matter parsing #69023
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Addressed the comments. :) |
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r=me after rebase |
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Same idea for `Unsafety` & use new span for better diagnostics.
use new span for better diagnostics.
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@bors r=petrochenkov |
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📌 Commit 9828559 has been approved by |
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parse: unify function front matter parsing Part of #68728. - `const extern fn` feature gating is now done post-expansion such that we do not have conditional compatibilities of function qualifiers *in parsing*. - The `FnFrontMatter` grammar becomes: ```rust Extern = "extern" StringLit ; FnQual = "const"? "async"? "unsafe"? Extern? ; FnFrontMatter = FnQual "fn" ; ``` That is, all item contexts now *syntactically* allow `const async unsafe extern "C" fn` and use semantic restrictions to rule out combinations previously prevented syntactically. The semantic restrictions include in particular: - `fn`s in `extern { ... }` can have no qualifiers. - `const` and `async` cannot be combined. - We change `ast::{Unsafety, Spanned<Constness>}>` into `enum ast::{Unsafe, Const} { Yes(Span), No }` respectively. This change in formulation allow us to exclude `Span` in the case of `No`, which facilitates parsing. Moreover, we also add a `Span` to `IsAsync` which is renamed to `Async`. The new `Span`s in `Unsafety` and `Async` are then taken advantage of for better diagnostics. A reason this change was made is to have a more uniform and clear naming scheme. The HIR keeps the structures in AST (with those definitions moved into HIR) for now to avoid regressing perf. r? @petrochenkov
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☀️ Test successful - checks-azure |
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📣 Toolstate changed by #69023! Tested on commit be493fe. 💔 rustc-guide on linux: test-pass → test-fail (cc @JohnTitor @amanjeev @spastorino @mark-i-m, @rust-lang/infra). |
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Tested on commit rust-lang/rust@be493fe. Direct link to PR: <rust-lang/rust#69023> 💔 rustc-guide on linux: test-pass → test-fail (cc @JohnTitor @amanjeev @spastorino @mark-i-m, @rust-lang/infra).
This was referenced Feb 13, 2020
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(Toolstate failure is spurious, can be ignored.) |
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Part of #68728.
const extern fnfeature gating is now done post-expansion such that we do not have conditional compatibilities of function qualifiers in parsing.The
FnFrontMattergrammar becomes:That is, all item contexts now syntactically allow
const async unsafe extern "C" fnand use semantic restrictions to rule out combinations previously prevented syntactically. The semantic restrictions include in particular:fns inextern { ... }can have no qualifiers.constandasynccannot be combined.We change
ast::{Unsafety, Spanned<Constness>}>intoenum ast::{Unsafe, Const} { Yes(Span), No }respectively. This change in formulation allow us to excludeSpanin the case ofNo, which facilitates parsing. Moreover, we also add aSpantoIsAsyncwhich is renamed toAsync. The newSpans inUnsafetyandAsyncare then taken advantage of for better diagnostics. A reason this change was made is to have a more uniform and clear naming scheme.The HIR keeps the structures in AST (with those definitions moved into HIR) for now to avoid regressing perf.
r? @petrochenkov