Auto merge of #57282 - matthewjasper:wellformed-return-ty, r=nikomatsakis
Wf-check the output type of a function in MIR-typeck Closes #57265 cc @scalexm
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commit
140936307e
4 changed files with 40 additions and 2 deletions
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@ -1452,7 +1452,7 @@ impl<'a, 'gcx, 'tcx> TypeChecker<'a, 'gcx, 'tcx> {
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self.check_call_dest(mir, term, &sig, destination, term_location);
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self.check_call_dest(mir, term, &sig, destination, term_location);
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self.prove_predicates(
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self.prove_predicates(
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sig.inputs().iter().map(|ty| ty::Predicate::WellFormed(ty)),
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sig.inputs_and_output.iter().map(|ty| ty::Predicate::WellFormed(ty)),
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term_location.to_locations(),
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term_location.to_locations(),
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ConstraintCategory::Boring,
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ConstraintCategory::Boring,
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);
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);
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@ -76,7 +76,7 @@ pub trait Machine<'a, 'mir, 'tcx>: Sized {
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type MemoryExtra: Default;
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type MemoryExtra: Default;
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/// Extra data stored in every allocation.
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/// Extra data stored in every allocation.
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type AllocExtra: AllocationExtra<Self::PointerTag, Self::MemoryExtra>;
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type AllocExtra: AllocationExtra<Self::PointerTag, Self::MemoryExtra> + 'static;
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/// Memory's allocation map
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/// Memory's allocation map
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type MemoryMap:
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type MemoryMap:
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26
src/test/ui/nll/issue-57265-return-type-wf-check.rs
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26
src/test/ui/nll/issue-57265-return-type-wf-check.rs
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@ -0,0 +1,26 @@
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#![feature(nll)]
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use std::any::Any;
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#[derive(Debug, Clone)]
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struct S<T: 'static>(T);
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// S<&'a T> is in the return type, so we get an implied bound
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// &'a T: 'static
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fn foo<'a, T>(x: &'a T) -> (S<&'a T>, Box<dyn Any + 'static>) {
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let y = S(x);
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let z = Box::new(y.clone()) as Box<dyn Any + 'static>;
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(y, z)
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}
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fn main() {
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let x = 5;
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// Check that we require that the argument is of type `&'static String`,
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// so that the return type is well-formed.
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let (_, z) = foo(&"hello".to_string());
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//~^ ERROR temporary value dropped while borrowed
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println!("{:?}", z.downcast_ref::<S<&'static String>>());
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}
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12
src/test/ui/nll/issue-57265-return-type-wf-check.stderr
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src/test/ui/nll/issue-57265-return-type-wf-check.stderr
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@ -0,0 +1,12 @@
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error[E0716]: temporary value dropped while borrowed
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--> $DIR/issue-57265-return-type-wf-check.rs:22:23
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LL | let (_, z) = foo(&"hello".to_string());
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| -----^^^^^^^^^^^^^^^^^^^-- temporary value is freed at the end of this statement
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| | |
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| | creates a temporary which is freed while still in use
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| argument requires that borrow lasts for `'static`
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error: aborting due to previous error
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For more information about this error, try `rustc --explain E0716`.
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