Rollup merge of #145604 - compiler-errors:static-closure, r=fmease

Gate static closures behind a parser feature

I'd like to gate `static ||` closures behind a feature gate, since we shouldn't allow people to take advantage of this syntax if it's currently unstable. Right now, since it's only rejected after ast lowering, it's accessible to macros.

Let's crater this to see if we can claw it back without breaking anyone's code.

compiler/rustc_ast_passes/src/feature_gate.rs

@@ -524,6 +524,7 @@ pub fn check_crate(krate: &ast::Crate, sess: &Session, features: &Features) {
     gate_all!(where_clause_attrs, "attributes in `where` clause are unstable");
     gate_all!(super_let, "`super let` is experimental");
     gate_all!(frontmatter, "frontmatters are experimental");
+    gate_all!(coroutines, "coroutine syntax is experimental");
 
     if !visitor.features.never_patterns() {
         if let Some(spans) = spans.get(&sym::never_patterns) {

compiler/rustc_parse/src/parser/expr.rs

@@ -2409,8 +2409,12 @@ impl<'a> Parser<'a> {
 
         let constness = self.parse_closure_constness();
 
-        let movability =
-            if self.eat_keyword(exp!(Static)) { Movability::Static } else { Movability::Movable };
+        let movability = if self.eat_keyword(exp!(Static)) {
+            self.psess.gated_spans.gate(sym::coroutines, self.prev_token.span);
+            Movability::Static
+        } else {
+            Movability::Movable
+        };
 
         let coroutine_kind = if self.token_uninterpolated_span().at_least_rust_2018() {
             self.parse_coroutine_kind(Case::Sensitive)

tests/ui/coroutine/static-closure-unexpanded.rs

@@ -0,0 +1,10 @@
+// Tests that static closures are not stable in the parser grammar unless the
+// coroutine feature is enabled.
+
+#[cfg(any())]
+fn foo() {
+    let _ = static || {};
+    //~^ ERROR coroutine syntax is experimental
+}
+
+fn main() {}

tests/ui/coroutine/static-closure-unexpanded.stderr

@@ -0,0 +1,13 @@
+error[E0658]: coroutine syntax is experimental
+  --> $DIR/static-closure-unexpanded.rs:6:13
+   |
+LL |     let _ = static || {};
+   |             ^^^^^^
+   |
+   = note: see issue #43122 <https://github.com/rust-lang/rust/issues/43122> for more information
+   = help: add `#![feature(coroutines)]` to the crate attributes to enable
+   = note: this compiler was built on YYYY-MM-DD; consider upgrading it if it is out of date
+
+error: aborting due to 1 previous error
+
+For more information about this error, try `rustc --explain E0658`.

tests/ui/static/static-closures.rs

@@ -1,4 +1,5 @@
 fn main() {
     static || {};
     //~^ ERROR closures cannot be static
+    //~| ERROR coroutine syntax is experimental
 }

tests/ui/static/static-closures.stderr

@@ -1,9 +1,20 @@
+error[E0658]: coroutine syntax is experimental
+  --> $DIR/static-closures.rs:2:5
+   |
+LL |     static || {};
+   |     ^^^^^^
+   |
+   = note: see issue #43122 <https://github.com/rust-lang/rust/issues/43122> for more information
+   = help: add `#![feature(coroutines)]` to the crate attributes to enable
+   = note: this compiler was built on YYYY-MM-DD; consider upgrading it if it is out of date
+
 error[E0697]: closures cannot be static
   --> $DIR/static-closures.rs:2:5
    |
 LL |     static || {};
    |     ^^^^^^^^^
 
-error: aborting due to 1 previous error
+error: aborting due to 2 previous errors
 
-For more information about this error, try `rustc --explain E0697`.
+Some errors have detailed explanations: E0658, E0697.
+For more information about an error, try `rustc --explain E0658`.

tests/ui/unpretty/exhaustive.expanded.stdout

@@ -13,6 +13,7 @@
 #![feature(box_patterns)]
 #![feature(builtin_syntax)]
 #![feature(const_trait_impl)]
+#![feature(coroutines)]
 #![feature(decl_macro)]
 #![feature(deref_patterns)]
 #![feature(explicit_tail_calls)]

tests/ui/unpretty/exhaustive.hir.stderr

@@ -1,17 +1,17 @@
 error[E0697]: closures cannot be static
-  --> $DIR/exhaustive.rs:209:9
+  --> $DIR/exhaustive.rs:210:9
    |
 LL |         static || value;
    |         ^^^^^^^^^
 
 error[E0697]: closures cannot be static
-  --> $DIR/exhaustive.rs:210:9
+  --> $DIR/exhaustive.rs:211:9
    |
 LL |         static move || value;
    |         ^^^^^^^^^^^^^^
 
 error[E0728]: `await` is only allowed inside `async` functions and blocks
-  --> $DIR/exhaustive.rs:239:13
+  --> $DIR/exhaustive.rs:240:13
    |
 LL |     fn expr_await() {
    |     --------------- this is not `async`
@@ -20,19 +20,19 @@ LL |         fut.await;
    |             ^^^^^ only allowed inside `async` functions and blocks
 
 error: in expressions, `_` can only be used on the left-hand side of an assignment
-  --> $DIR/exhaustive.rs:288:9
+  --> $DIR/exhaustive.rs:289:9
    |
 LL |         _;
    |         ^ `_` not allowed here
 
 error[E0214]: parenthesized type parameters may only be used with a `Fn` trait
-  --> $DIR/exhaustive.rs:298:9
+  --> $DIR/exhaustive.rs:299:9
    |
 LL |         x::();
    |         ^^^^^ only `Fn` traits may use parentheses
 
 error[E0214]: parenthesized type parameters may only be used with a `Fn` trait
-  --> $DIR/exhaustive.rs:299:9
+  --> $DIR/exhaustive.rs:300:9
    |
 LL |         x::(T, T) -> T;
    |         ^^^^^^^^^^^^^^ only `Fn` traits may use parentheses
@@ -44,31 +44,31 @@ LL +         x::<T, T> -> T;
    |
 
 error[E0214]: parenthesized type parameters may only be used with a `Fn` trait
-  --> $DIR/exhaustive.rs:300:9
+  --> $DIR/exhaustive.rs:301:9
    |
 LL |         crate::() -> ()::expressions::() -> ()::expr_path;
    |         ^^^^^^^^^^^^^^^ only `Fn` traits may use parentheses
 
 error[E0214]: parenthesized type parameters may only be used with a `Fn` trait
-  --> $DIR/exhaustive.rs:300:26
+  --> $DIR/exhaustive.rs:301:26
    |
 LL |         crate::() -> ()::expressions::() -> ()::expr_path;
    |                          ^^^^^^^^^^^^^^^^^^^^^ only `Fn` traits may use parentheses
 
 error[E0214]: parenthesized type parameters may only be used with a `Fn` trait
-  --> $DIR/exhaustive.rs:303:9
+  --> $DIR/exhaustive.rs:304:9
    |
 LL |         core::()::marker::()::PhantomData;
    |         ^^^^^^^^ only `Fn` traits may use parentheses
 
 error[E0214]: parenthesized type parameters may only be used with a `Fn` trait
-  --> $DIR/exhaustive.rs:303:19
+  --> $DIR/exhaustive.rs:304:19
    |
 LL |         core::()::marker::()::PhantomData;
    |                   ^^^^^^^^^^ only `Fn` traits may use parentheses
 
 error: `yield` can only be used in `#[coroutine]` closures, or `gen` blocks
-  --> $DIR/exhaustive.rs:390:9
+  --> $DIR/exhaustive.rs:391:9
    |
 LL |         yield;
    |         ^^^^^
@@ -79,7 +79,7 @@ LL |     #[coroutine] fn expr_yield() {
    |     ++++++++++++
 
 error[E0703]: invalid ABI: found `C++`
-  --> $DIR/exhaustive.rs:470:23
+  --> $DIR/exhaustive.rs:471:23
    |
 LL |         unsafe extern "C++" {}
    |                       ^^^^^ invalid ABI
@@ -87,7 +87,7 @@ LL |         unsafe extern "C++" {}
    = note: invoke `rustc --print=calling-conventions` for a full list of supported calling conventions
 
 error: `..` patterns are not allowed here
-  --> $DIR/exhaustive.rs:677:13
+  --> $DIR/exhaustive.rs:678:13
    |
 LL |         let ..;
    |             ^^
@@ -95,13 +95,13 @@ LL |         let ..;
    = note: only allowed in tuple, tuple struct, and slice patterns
 
 error[E0214]: parenthesized type parameters may only be used with a `Fn` trait
-  --> $DIR/exhaustive.rs:792:16
+  --> $DIR/exhaustive.rs:793:16
    |
 LL |         let _: T() -> !;
    |                ^^^^^^^^ only `Fn` traits may use parentheses
 
 error[E0562]: `impl Trait` is not allowed in the type of variable bindings
-  --> $DIR/exhaustive.rs:806:16
+  --> $DIR/exhaustive.rs:807:16
    |
 LL |         let _: impl Send;
    |                ^^^^^^^^^
@@ -112,7 +112,7 @@ LL |         let _: impl Send;
    = note: this compiler was built on YYYY-MM-DD; consider upgrading it if it is out of date
 
 error[E0562]: `impl Trait` is not allowed in the type of variable bindings
-  --> $DIR/exhaustive.rs:807:16
+  --> $DIR/exhaustive.rs:808:16
    |
 LL |         let _: impl Send + 'static;
    |                ^^^^^^^^^^^^^^^^^^^
@@ -123,7 +123,7 @@ LL |         let _: impl Send + 'static;
    = note: this compiler was built on YYYY-MM-DD; consider upgrading it if it is out of date
 
 error[E0562]: `impl Trait` is not allowed in the type of variable bindings
-  --> $DIR/exhaustive.rs:808:16
+  --> $DIR/exhaustive.rs:809:16
    |
 LL |         let _: impl 'static + Send;
    |                ^^^^^^^^^^^^^^^^^^^
@@ -134,7 +134,7 @@ LL |         let _: impl 'static + Send;
    = note: this compiler was built on YYYY-MM-DD; consider upgrading it if it is out of date
 
 error[E0562]: `impl Trait` is not allowed in the type of variable bindings
-  --> $DIR/exhaustive.rs:809:16
+  --> $DIR/exhaustive.rs:810:16
    |
 LL |         let _: impl ?Sized;
    |                ^^^^^^^^^^^
@@ -145,7 +145,7 @@ LL |         let _: impl ?Sized;
    = note: this compiler was built on YYYY-MM-DD; consider upgrading it if it is out of date
 
 error[E0562]: `impl Trait` is not allowed in the type of variable bindings
-  --> $DIR/exhaustive.rs:810:16
+  --> $DIR/exhaustive.rs:811:16
    |
 LL |         let _: impl [const] Clone;
    |                ^^^^^^^^^^^^^^^^^^
@@ -156,7 +156,7 @@ LL |         let _: impl [const] Clone;
    = note: this compiler was built on YYYY-MM-DD; consider upgrading it if it is out of date
 
 error[E0562]: `impl Trait` is not allowed in the type of variable bindings
-  --> $DIR/exhaustive.rs:811:16
+  --> $DIR/exhaustive.rs:812:16
    |
 LL |         let _: impl for<'a> Send;
    |                ^^^^^^^^^^^^^^^^^

tests/ui/unpretty/exhaustive.hir.stdout

@@ -12,6 +12,7 @@
 #![feature(box_patterns)]
 #![feature(builtin_syntax)]
 #![feature(const_trait_impl)]
+#![feature(coroutines)]
 #![feature(decl_macro)]
 #![feature(deref_patterns)]
 #![feature(explicit_tail_calls)]

tests/ui/unpretty/exhaustive.rs

@@ -12,6 +12,7 @@
 #![feature(box_patterns)]
 #![feature(builtin_syntax)]
 #![feature(const_trait_impl)]
+#![feature(coroutines)]
 #![feature(decl_macro)]
 #![feature(deref_patterns)]
 #![feature(explicit_tail_calls)]