Rollup merge of #91140 - nbdd0121:const_typeck, r=oli-obk

Split inline const to two feature gates and mark expression position inline const complete

This PR splits inline const in pattern position into its own `#![feature(inline_const_pat)]` feature gate, and make the usage in expression position complete.

I think I have resolved most outstanding issues related to `inline_const` with #89561 and other PRs. The only thing left that I am aware of is #90150 and the lack of lifetime checks when inline const is used in pattern position (FIXME in #89561). Implementation-wise when used in pattern position it has to be lowered during MIR building while in expression position it's evaluated only when monomorphizing (just like normal consts), so it makes some sense to separate it into two feature gates so one can progress without being blocked by another.

``@rustbot`` label: T-compiler F-inline_const

32 files changed, 72 insertions, 43 deletions

diff --git a/compiler/rustc_ast_passes/src/feature_gate.rs b/compiler/rustc_ast_passes/src/feature_gate.rs
index b011a2e8117..6a19984f8ea 100644
--- a/compiler/rustc_ast_passes/src/feature_gate.rs
+++ b/compiler/rustc_ast_passes/src/feature_gate.rs
@@ -719,6 +719,7 @@ pub fn check_crate(krate: &ast::Crate, sess: &Session) {
     gate_all!(const_trait_impl, "const trait impls are experimental");
     gate_all!(half_open_range_patterns, "half-open range patterns are unstable");
     gate_all!(inline_const, "inline-const is experimental");
+    gate_all!(inline_const_pat, "inline-const in pattern position is experimental");
     gate_all!(
         const_generics_defaults,
         "default values for const generic parameters are experimental"
diff --git a/compiler/rustc_feature/src/active.rs b/compiler/rustc_feature/src/active.rs
index 608581306be..c34ecc966d0 100644
--- a/compiler/rustc_feature/src/active.rs
+++ b/compiler/rustc_feature/src/active.rs
@@ -409,7 +409,9 @@ declare_features! (
     /// Allows associated types in inherent impls.
     (incomplete, inherent_associated_types, "1.52.0", Some(8995), None),
     /// Allow anonymous constants from an inline `const` block
-    (incomplete, inline_const, "1.49.0", Some(76001), None),
+    (active, inline_const, "1.49.0", Some(76001), None),
+    /// Allow anonymous constants from an inline `const` block in pattern position
+    (incomplete, inline_const_pat, "1.58.0", Some(76001), None),
     /// Allows using `pointer` and `reference` in intra-doc links
     (active, intra_doc_pointers, "1.51.0", Some(80896), None),
     /// Allows `#[instruction_set(_)]` attribute
diff --git a/compiler/rustc_parse/src/parser/expr.rs b/compiler/rustc_parse/src/parser/expr.rs
index 0c8c45410bd..3669a4fce9c 100644
--- a/compiler/rustc_parse/src/parser/expr.rs
+++ b/compiler/rustc_parse/src/parser/expr.rs
@@ -1243,7 +1243,7 @@ impl<'a> Parser<'a> {
         } else if self.eat_keyword(kw::Unsafe) {
             self.parse_block_expr(None, lo, BlockCheckMode::Unsafe(ast::UserProvided), attrs)
         } else if self.check_inline_const(0) {
-            self.parse_const_block(lo.to(self.token.span))
+            self.parse_const_block(lo.to(self.token.span), false)
         } else if self.is_do_catch_block() {
             self.recover_do_catch(attrs)
         } else if self.is_try_block() {
diff --git a/compiler/rustc_parse/src/parser/mod.rs b/compiler/rustc_parse/src/parser/mod.rs
index e50b983ec62..9212aaa87d1 100644
--- a/compiler/rustc_parse/src/parser/mod.rs
+++ b/compiler/rustc_parse/src/parser/mod.rs
@@ -1095,8 +1095,12 @@ impl<'a> Parser<'a> {
     }
 
     /// Parses inline const expressions.
-    fn parse_const_block(&mut self, span: Span) -> PResult<'a, P<Expr>> {
-        self.sess.gated_spans.gate(sym::inline_const, span);
+    fn parse_const_block(&mut self, span: Span, pat: bool) -> PResult<'a, P<Expr>> {
+        if pat {
+            self.sess.gated_spans.gate(sym::inline_const_pat, span);
+        } else {
+            self.sess.gated_spans.gate(sym::inline_const, span);
+        }
         self.eat_keyword(kw::Const);
         let blk = self.parse_block()?;
         let anon_const = AnonConst {
diff --git a/compiler/rustc_parse/src/parser/pat.rs b/compiler/rustc_parse/src/parser/pat.rs
index 3b5a297103c..bb3947bb47a 100644
--- a/compiler/rustc_parse/src/parser/pat.rs
+++ b/compiler/rustc_parse/src/parser/pat.rs
@@ -437,7 +437,7 @@ impl<'a> Parser<'a> {
             PatKind::Box(pat)
         } else if self.check_inline_const(0) {
             // Parse `const pat`
-            let const_expr = self.parse_const_block(lo.to(self.token.span))?;
+            let const_expr = self.parse_const_block(lo.to(self.token.span), true)?;
 
             if let Some(re) = self.parse_range_end() {
                 self.parse_pat_range_begin_with(const_expr, re)?
@@ -884,7 +884,7 @@ impl<'a> Parser<'a> {
 
     fn parse_pat_range_end(&mut self) -> PResult<'a, P<Expr>> {
         if self.check_inline_const(0) {
-            self.parse_const_block(self.token.span)
+            self.parse_const_block(self.token.span, true)
         } else if self.check_path() {
             let lo = self.token.span;
             let (qself, path) = if self.eat_lt() {
diff --git a/compiler/rustc_span/src/symbol.rs b/compiler/rustc_span/src/symbol.rs
index 9064d0c4969..c34cf822765 100644
--- a/compiler/rustc_span/src/symbol.rs
+++ b/compiler/rustc_span/src/symbol.rs
@@ -732,6 +732,7 @@ symbols! {
         inlateout,
         inline,
         inline_const,
+        inline_const_pat,
         inout,
         instruction_set,
         intel,
diff --git a/src/doc/unstable-book/src/language-features/inline-const-pat.md b/src/doc/unstable-book/src/language-features/inline-const-pat.md
new file mode 100644
index 00000000000..5f0f7547a0a
--- /dev/null
+++ b/src/doc/unstable-book/src/language-features/inline-const-pat.md
@@ -0,0 +1,24 @@
+# `inline_const_pat`
+
+The tracking issue for this feature is: [#76001]
+
+See also [`inline_const`](inline-const.md)
+
+------
+
+This feature allows you to use inline constant expressions in pattern position:
+
+```rust
+#![feature(inline_const_pat)]
+
+const fn one() -> i32 { 1 }
+
+let some_int = 3;
+match some_int {
+    const { 1 + 2 } => println!("Matched 1 + 2"),
+    const { one() } => println!("Matched const fn returning 1"),
+    _ => println!("Didn't match anything :("),
+}
+```
+
+[#76001]: https://github.com/rust-lang/rust/issues/76001
diff --git a/src/doc/unstable-book/src/language-features/inline-const.md b/src/doc/unstable-book/src/language-features/inline-const.md
index 00e1c79ca3f..7be70eed6ce 100644
--- a/src/doc/unstable-book/src/language-features/inline-const.md
+++ b/src/doc/unstable-book/src/language-features/inline-const.md
@@ -2,6 +2,8 @@
 
 The tracking issue for this feature is: [#76001]
 
+See also [`inline_const_pat`](inline-const-pat.md)
+
 ------
 
 This feature allows you to use inline constant expressions. For example, you can
@@ -27,19 +29,4 @@ fn main() {
 }
 ```
 
-You can also use inline constant expressions in patterns:
-
-```rust
-#![feature(inline_const)]
-
-const fn one() -> i32 { 1 }
-
-let some_int = 3;
-match some_int {
-    const { 1 + 2 } => println!("Matched 1 + 2"),
-    const { one() } => println!("Matched const fn returning 1"),
-    _ => println!("Didn't match anything :("),
-}
-```
-
 [#76001]: https://github.com/rust-lang/rust/issues/76001
diff --git a/src/test/ui/consts/closure-structural-match-issue-90013.rs b/src/test/ui/consts/closure-structural-match-issue-90013.rs
index 7853ee41a90..1952ddb941e 100644
--- a/src/test/ui/consts/closure-structural-match-issue-90013.rs
+++ b/src/test/ui/consts/closure-structural-match-issue-90013.rs
@@ -1,6 +1,5 @@
 // Regression test for issue 90013.
 // check-pass
-#![allow(incomplete_features)]
 #![feature(inline_const)]
 
 fn main() {
diff --git a/src/test/ui/consts/const-blocks/fn-call-in-const.rs b/src/test/ui/consts/const-blocks/fn-call-in-const.rs
index 7936af75d84..20496f62712 100644
--- a/src/test/ui/consts/const-blocks/fn-call-in-const.rs
+++ b/src/test/ui/consts/const-blocks/fn-call-in-const.rs
@@ -1,7 +1,7 @@
 // run-pass
 
 #![feature(inline_const)]
-#![allow(unused, incomplete_features)]
+#![allow(unused)]
 
 // Some type that is not copyable.
 struct Bar;
diff --git a/src/test/ui/feature-gates/feature-gate-inline_const_pat.rs b/src/test/ui/feature-gates/feature-gate-inline_const_pat.rs
new file mode 100644
index 00000000000..3d0df289fb7
--- /dev/null
+++ b/src/test/ui/feature-gates/feature-gate-inline_const_pat.rs
@@ -0,0 +1,4 @@
+fn main() {
+    let const { () } = ();
+    //~^ ERROR inline-const in pattern position is experimental [E0658]
+}
diff --git a/src/test/ui/feature-gates/feature-gate-inline_const_pat.stderr b/src/test/ui/feature-gates/feature-gate-inline_const_pat.stderr
new file mode 100644
index 00000000000..ca533d8505c
--- /dev/null
+++ b/src/test/ui/feature-gates/feature-gate-inline_const_pat.stderr
@@ -0,0 +1,12 @@
+error[E0658]: inline-const in pattern position is experimental
+  --> $DIR/feature-gate-inline_const_pat.rs:2:9
+   |
+LL |     let const { () } = ();
+   |         ^^^^^
+   |
+   = note: see issue #76001 <https://github.com/rust-lang/rust/issues/76001> for more information
+   = help: add `#![feature(inline_const_pat)]` to the crate attributes to enable
+
+error: aborting due to previous error
+
+For more information about this error, try `rustc --explain E0658`.
diff --git a/src/test/ui/half-open-range-patterns/range_pat_interactions0.rs b/src/test/ui/half-open-range-patterns/range_pat_interactions0.rs
index 4f478a69881..8f745e8104f 100644
--- a/src/test/ui/half-open-range-patterns/range_pat_interactions0.rs
+++ b/src/test/ui/half-open-range-patterns/range_pat_interactions0.rs
@@ -2,7 +2,7 @@
 #![allow(incomplete_features)]
 #![feature(exclusive_range_pattern)]
 #![feature(half_open_range_patterns)]
-#![feature(inline_const)]
+#![feature(inline_const_pat)]
 
 fn main() {
     let mut if_lettable = vec![];
diff --git a/src/test/ui/half-open-range-patterns/range_pat_interactions3.rs b/src/test/ui/half-open-range-patterns/range_pat_interactions3.rs
index 0afb5126059..41c7e46dfc1 100644
--- a/src/test/ui/half-open-range-patterns/range_pat_interactions3.rs
+++ b/src/test/ui/half-open-range-patterns/range_pat_interactions3.rs
@@ -12,7 +12,7 @@ fn main() {
             y @ (0..5 | 6) => or_two.push(y),
             //~^ exclusive range pattern syntax is experimental
             y @ 0..const { 5 + 1 } => assert_eq!(y, 5),
-            //~^ inline-const is experimental
+            //~^ inline-const in pattern position is experimental
             //~| exclusive range pattern syntax is experimental
             y @ -5.. => range_from.push(y),
             y @ ..-7 => assert_eq!(y, -8),
diff --git a/src/test/ui/half-open-range-patterns/range_pat_interactions3.stderr b/src/test/ui/half-open-range-patterns/range_pat_interactions3.stderr
index 8278e7cc6cf..5e36996a462 100644
--- a/src/test/ui/half-open-range-patterns/range_pat_interactions3.stderr
+++ b/src/test/ui/half-open-range-patterns/range_pat_interactions3.stderr
@@ -7,14 +7,14 @@ LL |             y @ ..-7 => assert_eq!(y, -8),
    = note: see issue #67264 <https://github.com/rust-lang/rust/issues/67264> for more information
    = help: add `#![feature(half_open_range_patterns)]` to the crate attributes to enable
 
-error[E0658]: inline-const is experimental
+error[E0658]: inline-const in pattern position is experimental
   --> $DIR/range_pat_interactions3.rs:14:20
    |
 LL |             y @ 0..const { 5 + 1 } => assert_eq!(y, 5),
    |                    ^^^^^
    |
    = note: see issue #76001 <https://github.com/rust-lang/rust/issues/76001> for more information
-   = help: add `#![feature(inline_const)]` to the crate attributes to enable
+   = help: add `#![feature(inline_const_pat)]` to the crate attributes to enable
 
 error[E0658]: exclusive range pattern syntax is experimental
   --> $DIR/range_pat_interactions3.rs:10:17
diff --git a/src/test/ui/inline-const/const-expr-array-init.rs b/src/test/ui/inline-const/const-expr-array-init.rs
index 8bb5dab1fa0..8a92cdbc0f9 100644
--- a/src/test/ui/inline-const/const-expr-array-init.rs
+++ b/src/test/ui/inline-const/const-expr-array-init.rs
@@ -1,6 +1,5 @@
 // build-pass
 
-#![allow(incomplete_features)]
 #![feature(inline_const)]
 
 use std::cell::Cell;
diff --git a/src/test/ui/inline-const/const-expr-basic.rs b/src/test/ui/inline-const/const-expr-basic.rs
index 9254c96a1e7..dac46fe25ec 100644
--- a/src/test/ui/inline-const/const-expr-basic.rs
+++ b/src/test/ui/inline-const/const-expr-basic.rs
@@ -1,7 +1,7 @@
 // run-pass
 
-#![allow(incomplete_features)]
 #![feature(inline_const)]
+
 fn foo() -> i32 {
     const {
         let x = 5 + 10;
diff --git a/src/test/ui/inline-const/const-expr-inference.rs b/src/test/ui/inline-const/const-expr-inference.rs
index 6aa2a2f3367..0d5892a74d9 100644
--- a/src/test/ui/inline-const/const-expr-inference.rs
+++ b/src/test/ui/inline-const/const-expr-inference.rs
@@ -1,7 +1,6 @@
 // check-pass
 
 #![feature(inline_const)]
-#![allow(incomplete_features)]
 
 pub fn todo<T>() -> T {
     const { todo!() }
diff --git a/src/test/ui/inline-const/const-expr-lifetime-err.rs b/src/test/ui/inline-const/const-expr-lifetime-err.rs
index e56cbc94038..0a032a7338a 100644
--- a/src/test/ui/inline-const/const-expr-lifetime-err.rs
+++ b/src/test/ui/inline-const/const-expr-lifetime-err.rs
@@ -1,4 +1,3 @@
-#![allow(incomplete_features)]
 #![feature(const_mut_refs)]
 #![feature(inline_const)]
 
diff --git a/src/test/ui/inline-const/const-expr-lifetime-err.stderr b/src/test/ui/inline-const/const-expr-lifetime-err.stderr
index 30ecd338a85..a23f7c9a796 100644
--- a/src/test/ui/inline-const/const-expr-lifetime-err.stderr
+++ b/src/test/ui/inline-const/const-expr-lifetime-err.stderr
@@ -1,5 +1,5 @@
 error[E0597]: `y` does not live long enough
-  --> $DIR/const-expr-lifetime-err.rs:24:30
+  --> $DIR/const-expr-lifetime-err.rs:23:30
    |
 LL | fn foo<'a>() {
    |        -- lifetime `'a` defined here
diff --git a/src/test/ui/inline-const/const-expr-lifetime.rs b/src/test/ui/inline-const/const-expr-lifetime.rs
index f622f2cbddf..d883deb2845 100644
--- a/src/test/ui/inline-const/const-expr-lifetime.rs
+++ b/src/test/ui/inline-const/const-expr-lifetime.rs
@@ -1,6 +1,5 @@
 // run-pass
 
-#![allow(incomplete_features)]
 #![feature(const_mut_refs)]
 #![feature(inline_const)]
 
diff --git a/src/test/ui/inline-const/const-expr-macro.rs b/src/test/ui/inline-const/const-expr-macro.rs
index 66b58571751..041f3e15a29 100644
--- a/src/test/ui/inline-const/const-expr-macro.rs
+++ b/src/test/ui/inline-const/const-expr-macro.rs
@@ -1,7 +1,7 @@
 // run-pass
 
-#![allow(incomplete_features)]
 #![feature(inline_const)]
+
 macro_rules! do_const_block{
     ($val:block) => { const $val }
 }
diff --git a/src/test/ui/inline-const/const-expr-reference.rs b/src/test/ui/inline-const/const-expr-reference.rs
index 747f14e4bd0..a54d879f69d 100644
--- a/src/test/ui/inline-const/const-expr-reference.rs
+++ b/src/test/ui/inline-const/const-expr-reference.rs
@@ -1,6 +1,5 @@
 // run-pass
 
-#![allow(incomplete_features)]
 #![feature(inline_const)]
 
 const fn bar() -> i32 {
diff --git a/src/test/ui/inline-const/const-match-pat-generic.rs b/src/test/ui/inline-const/const-match-pat-generic.rs
index 61680d653d0..4486411698a 100644
--- a/src/test/ui/inline-const/const-match-pat-generic.rs
+++ b/src/test/ui/inline-const/const-match-pat-generic.rs
@@ -1,5 +1,5 @@
 #![allow(incomplete_features)]
-#![feature(inline_const)]
+#![feature(inline_const_pat)]
 
 // rust-lang/rust#82518: ICE with inline-const in match referencing const-generic parameter
 
diff --git a/src/test/ui/inline-const/const-match-pat-inference.rs b/src/test/ui/inline-const/const-match-pat-inference.rs
index 61188ed5d47..d83ae6e9834 100644
--- a/src/test/ui/inline-const/const-match-pat-inference.rs
+++ b/src/test/ui/inline-const/const-match-pat-inference.rs
@@ -1,6 +1,6 @@
 // check-pass
 
-#![feature(inline_const)]
+#![feature(inline_const_pat)]
 #![allow(incomplete_features)]
 
 fn main() {
diff --git a/src/test/ui/inline-const/const-match-pat-lifetime-err.rs b/src/test/ui/inline-const/const-match-pat-lifetime-err.rs
index bc5aa248944..436b8037f30 100644
--- a/src/test/ui/inline-const/const-match-pat-lifetime-err.rs
+++ b/src/test/ui/inline-const/const-match-pat-lifetime-err.rs
@@ -2,7 +2,7 @@
 
 #![allow(incomplete_features)]
 #![feature(const_mut_refs)]
-#![feature(inline_const)]
+#![feature(inline_const_pat)]
 
 use std::marker::PhantomData;
 
diff --git a/src/test/ui/inline-const/const-match-pat-lifetime.rs b/src/test/ui/inline-const/const-match-pat-lifetime.rs
index 3d986f0d9ee..6d943bbcc01 100644
--- a/src/test/ui/inline-const/const-match-pat-lifetime.rs
+++ b/src/test/ui/inline-const/const-match-pat-lifetime.rs
@@ -3,6 +3,7 @@
 #![allow(incomplete_features)]
 #![feature(const_mut_refs)]
 #![feature(inline_const)]
+#![feature(inline_const_pat)]
 
 use std::marker::PhantomData;
 
diff --git a/src/test/ui/inline-const/const-match-pat-range.rs b/src/test/ui/inline-const/const-match-pat-range.rs
index eefe43a1a22..7dc8c11355a 100644
--- a/src/test/ui/inline-const/const-match-pat-range.rs
+++ b/src/test/ui/inline-const/const-match-pat-range.rs
@@ -1,7 +1,7 @@
 // build-pass
 
 #![allow(incomplete_features)]
-#![feature(inline_const, half_open_range_patterns, exclusive_range_pattern)]
+#![feature(inline_const_pat, half_open_range_patterns, exclusive_range_pattern)]
 fn main() {
     const N: u32 = 10;
     let x: u32 = 3;
diff --git a/src/test/ui/inline-const/const-match-pat.rs b/src/test/ui/inline-const/const-match-pat.rs
index c0dc90d971a..2f55e16b35c 100644
--- a/src/test/ui/inline-const/const-match-pat.rs
+++ b/src/test/ui/inline-const/const-match-pat.rs
@@ -1,7 +1,7 @@
 // run-pass
 
 #![allow(incomplete_features)]
-#![feature(inline_const)]
+#![feature(inline_const_pat)]
 const MMIO_BIT1: u8 = 4;
 const MMIO_BIT2: u8 = 5;
 
diff --git a/src/test/ui/lint/dead-code/anon-const-in-pat.rs b/src/test/ui/lint/dead-code/anon-const-in-pat.rs
index 4c6211a279a..d3e39c0de69 100644
--- a/src/test/ui/lint/dead-code/anon-const-in-pat.rs
+++ b/src/test/ui/lint/dead-code/anon-const-in-pat.rs
@@ -1,5 +1,5 @@
 // check-pass
-#![feature(inline_const)]
+#![feature(inline_const_pat)]
 #![allow(incomplete_features)]
 #![deny(dead_code)]
 
diff --git a/src/test/ui/pattern/non-structural-match-types.rs b/src/test/ui/pattern/non-structural-match-types.rs
index 713418fc5b2..5c331547366 100644
--- a/src/test/ui/pattern/non-structural-match-types.rs
+++ b/src/test/ui/pattern/non-structural-match-types.rs
@@ -2,7 +2,7 @@
 #![allow(incomplete_features)]
 #![allow(unreachable_code)]
 #![feature(const_async_blocks)]
-#![feature(inline_const)]
+#![feature(inline_const_pat)]
 
 fn main() {
     match loop {} {
diff --git a/src/test/ui/simd/intrinsic/generic-elements-pass.rs b/src/test/ui/simd/intrinsic/generic-elements-pass.rs
index 08544bce45d..3c913c0adfa 100644
--- a/src/test/ui/simd/intrinsic/generic-elements-pass.rs
+++ b/src/test/ui/simd/intrinsic/generic-elements-pass.rs
@@ -2,7 +2,6 @@
 // ignore-emscripten FIXME(#45351) hits an LLVM assert
 
 #![feature(repr_simd, platform_intrinsics)]
-#![allow(incomplete_features)]
 #![feature(inline_const)]
 
 #[repr(simd)]