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Rollup merge of rust-lang#96004 - JakobDegen:fix-validator-ice, r=pet…
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…rochenkov

Consider lifetimes when comparing types for equality in MIR validator

Closes rust-lang#95978 .
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Dylan-DPC authored Apr 16, 2022
2 parents ac01c91 + d5f3863 commit a30dbc2
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Showing 3 changed files with 15 additions and 5 deletions.
7 changes: 3 additions & 4 deletions compiler/rustc_const_eval/src/transform/validate.rs
Original file line number Diff line number Diff line change
Expand Up @@ -315,9 +315,8 @@ impl<'a, 'tcx> Visitor<'tcx> for TypeChecker<'a, 'tcx> {
| ty::FnPtr(..)
)
}
// None of the possible types have lifetimes, so we can just compare
// directly
if a != b {
// The function pointer types can have lifetimes
if !self.mir_assign_valid_types(a, b) {
self.fail(
location,
format!("Cannot compare unequal types {:?} and {:?}", a, b),
Expand Down Expand Up @@ -464,7 +463,7 @@ impl<'a, 'tcx> Visitor<'tcx> for TypeChecker<'a, 'tcx> {
};
// since CopyNonOverlapping is parametrized by 1 type,
// we only need to check that they are equal and not keep an extra parameter.
if op_src_ty != op_dst_ty {
if !self.mir_assign_valid_types(op_src_ty, op_dst_ty) {
self.fail(location, format!("bad arg ({:?} != {:?})", op_src_ty, op_dst_ty));
}

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3 changes: 2 additions & 1 deletion compiler/rustc_middle/src/mir/mod.rs
Original file line number Diff line number Diff line change
Expand Up @@ -2518,7 +2518,8 @@ pub enum Rvalue<'tcx> {
/// * `Offset` has the same semantics as [`offset`](pointer::offset), except that the second
/// parameter may be a `usize` as well.
/// * The comparison operations accept `bool`s, `char`s, signed or unsigned integers, floats,
/// raw pointers, or function pointers of matching types and return a `bool`.
/// raw pointers, or function pointers and return a `bool`. The types of the operands must be
/// matching, up to the usual caveat of the lifetimes in function pointers.
/// * Left and right shift operations accept signed or unsigned integers not necessarily of the
/// same type and return a value of the same type as their LHS. Like in Rust, the RHS is
/// truncated as needed.
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10 changes: 10 additions & 0 deletions src/test/ui/mir/issue-95978-validator-lifetime-comparison.rs
Original file line number Diff line number Diff line change
@@ -0,0 +1,10 @@
// check-pass
// compile-flags: -Zvalidate-mir

fn foo(_a: &str) {}

fn main() {
let x = foo as fn(&'static str);

let _ = x == foo;
}

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