Rollup merge of #77415 - ecstatic-morse:const-checking-async-block, r=oli-obk
Better error message for `async` blocks in a const-context Improves the error message for the case in #77361. r? @oli-obk
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cac5352e33
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@ -151,14 +151,15 @@ impl NonConstOp for FnPtrCast {
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}
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#[derive(Debug)]
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pub struct Generator;
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pub struct Generator(pub hir::GeneratorKind);
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impl NonConstOp for Generator {
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fn status_in_item(&self, _: &ConstCx<'_, '_>) -> Status {
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Status::Forbidden
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}
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fn build_error(&self, ccx: &ConstCx<'_, 'tcx>, span: Span) -> DiagnosticBuilder<'tcx> {
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ccx.tcx.sess.struct_span_err(span, "Generators and `async` functions cannot be `const`")
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let msg = format!("{}s are not allowed in {}s", self.0, ccx.const_kind());
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ccx.tcx.sess.struct_span_err(span, &msg)
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}
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}
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@ -770,6 +770,14 @@ impl Visitor<'tcx> for Validator<'mir, 'tcx> {
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return;
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}
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// `async` blocks get lowered to `std::future::from_generator(/* a closure */)`.
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let is_async_block = Some(callee) == tcx.lang_items().from_generator_fn();
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if is_async_block {
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let kind = hir::GeneratorKind::Async(hir::AsyncGeneratorKind::Block);
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self.check_op(ops::Generator(kind));
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return;
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}
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// HACK: This is to "unstabilize" the `transmute` intrinsic
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// within const fns. `transmute` is allowed in all other const contexts.
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// This won't really scale to more intrinsics or functions. Let's allow const
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@ -869,7 +877,7 @@ impl Visitor<'tcx> for Validator<'mir, 'tcx> {
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TerminatorKind::Abort => self.check_op(ops::Abort),
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TerminatorKind::GeneratorDrop | TerminatorKind::Yield { .. } => {
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self.check_op(ops::Generator)
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self.check_op(ops::Generator(hir::GeneratorKind::Gen))
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}
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TerminatorKind::Assert { .. }
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8
src/test/ui/consts/async-block.rs
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8
src/test/ui/consts/async-block.rs
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@ -0,0 +1,8 @@
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// From <https://github.com/rust-lang/rust/issues/77361>
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// edition:2018
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const _: i32 = { core::mem::ManuallyDrop::new(async { 0 }); 4 };
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//~^ `async` block
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fn main() {}
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src/test/ui/consts/async-block.stderr
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8
src/test/ui/consts/async-block.stderr
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@ -0,0 +1,8 @@
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error: `async` blocks are not allowed in constants
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--> $DIR/async-block.rs:5:47
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LL | const _: i32 = { core::mem::ManuallyDrop::new(async { 0 }); 4 };
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| ^^^^^^^^^^^
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error: aborting due to previous error
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