Introduce macro sub-namespaces and macro_use prelude
#14781
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We've already removed non-sysroot proc macro server, which effectively removed support for Rust <1.64.0, so this removal of fallback path shouldn't be problem at this point.
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Veykril
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May 11, 2023
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That's quite a list of fixes by one PR, awesome 🎉 |
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☀️ Test successful - checks-actions |
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I think this broke some things. Of note is that the |
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Expand more single ident macro calls upon item collection Addresses #14781 (comment) I believe this (almost) brings the number of unresolved names back to pre-#14781: |r-a version|`analysis-stats compiler/rustc` (rust-lang/rust@69fef92) | |---|---| |pre-#14781 (b069eb7) | exprs: 2747778, ??ty: 122236 (4%), ?ty: 107826 (3%), !ty: 728 | | #14781 (a7944a9) | exprs: 2713080, ??ty: 139651 (5%), ?ty: 114444 (4%), !ty: 730 | | with this fix | exprs: 2747871, ??ty: 122237 (4%), ?ty: 108171 (3%), !ty: 676 | (I haven't investigated on the increase in some numbers but hopefully not too much of a problem) This is only a temporary solution. The core problem is that we haven't fully implemented the textual scope of legacy macros. For example, we *have been* failing to resolve `foo` in the following snippet, even before #14781 or after this patch. As noted in a FIXME, we need a way to resolve names in textual scope without eager expansion during item collection. ```rust //- /main.rs crate:main deps:lib lib::mk_foo!(); const A: i32 = foo!(); //^^^^^^ unresolved-macro-call //- /lib.rs crate:lib #[macro_export] macro_rules! mk_foo { () => { macro_rules! foo { () => { 42 } } } } ```
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This PR implements two mechanisms needed for correct macro name resolution: macro sub-namespace and
macro_useprelude.macro sub-namespaces
Macros have two sub-namespaces: one for function-like macro and the other for those in attributes (including custom derive macros). When we're resolving a macro name for function-like macro, we should ignore non-function-like macros, and vice versa.
This helps resolve single-segment macro names because we can (and should, as rustc does) fallback to names in preludes when the name in the current module scope is in different sub-namespace.
macro_useprelude#[macro_use]'d extern crate declarations (including the standard library) bring their macros into scope, but they should not be prioritized over local macros (those defined in place and those explicitly imported).We have been bringing them into legacy (textual) macro scope, which has the highest precedence in name resolution. This PR introduces the
macro_useprelude in crate-levelDefMaps, whose precedence is lower than local macros but higher than the standard library prelude.The first 3 commits are drive-by fixes/refactors.
Fixes #8828 (prelude)
Fixes #12505 (prelude)
Fixes #12734 (prelude)
Fixes #13683 (prelude)
Fixes #13821 (prelude)
Fixes #13974 (prelude)
Fixes #14254 (namespace)