diff --git a/compiler/rustc_hir_typeck/src/fn_ctxt/_impl.rs b/compiler/rustc_hir_typeck/src/fn_ctxt/_impl.rs index 786754ed12f09..bd2454f6368d3 100644 --- a/compiler/rustc_hir_typeck/src/fn_ctxt/_impl.rs +++ b/compiler/rustc_hir_typeck/src/fn_ctxt/_impl.rs @@ -279,13 +279,23 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> { } Entry::Occupied(mut entry) => { debug!(" - composing on top of {:?}", entry.get()); - match (&entry.get()[..], &adj[..]) { - // Applying any adjustment on top of a NeverToAny - // is a valid NeverToAny adjustment, because it can't - // be reached. - (&[Adjustment { kind: Adjust::NeverToAny, .. }], _) => return, + match (&mut entry.get_mut()[..], &adj[..]) { ( - &[ + [Adjustment { kind: Adjust::NeverToAny, target }], + &[.., Adjustment { target: new_target, .. }], + ) => { + // NeverToAny coercion can target any type, so instead of adding a new + // adjustment on top we can change the target. + // + // This is required for things like `a == a` (where `a: !`) to produce + // valid MIR -- we need borrow adjustment from things like `==` to change + // the type to `&!` (or `&()` depending on the fallback). This might be + // relevant even in unreachable code. + *target = new_target; + } + + ( + &mut [ Adjustment { kind: Adjust::Deref(_), .. }, Adjustment { kind: Adjust::Borrow(AutoBorrow::Ref(..)), .. }, ], @@ -294,11 +304,13 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> { .., // Any following adjustments are allowed. ], ) => { - // A reborrow has no effect before a dereference. + // A reborrow has no effect before a dereference, so we can safely replace adjustments. + *entry.get_mut() = adj; } - // FIXME: currently we never try to compose autoderefs - // and ReifyFnPointer/UnsafeFnPointer, but we could. + _ => { + // FIXME: currently we never try to compose autoderefs + // and ReifyFnPointer/UnsafeFnPointer, but we could. self.dcx().span_delayed_bug( expr.span, format!( @@ -308,9 +320,10 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> { adj ), ); + + *entry.get_mut() = adj; } } - *entry.get_mut() = adj; } } diff --git a/tests/mir-opt/building/eq_never_type._f.built.after.mir b/tests/mir-opt/building/eq_never_type._f.built.after.mir new file mode 100644 index 0000000000000..39438258c2ebb --- /dev/null +++ b/tests/mir-opt/building/eq_never_type._f.built.after.mir @@ -0,0 +1,53 @@ +// MIR for `_f` after built + +fn _f(_1: !, _2: !) -> () { + debug a => _1; + debug b => _2; + let mut _0: (); + let mut _3: !; + let _4: bool; + let mut _5: &(); + let mut _6: !; + let mut _7: &(); + let _8: (); + let mut _9: !; + + bb0: { + StorageLive(_4); + StorageLive(_5); + StorageLive(_6); + _6 = _1; + unreachable; + } + + bb1: { + StorageDead(_6); + StorageLive(_7); + StorageLive(_8); + StorageLive(_9); + _9 = _2; + unreachable; + } + + bb2: { + _7 = &_8; + StorageDead(_9); + _4 = <() as PartialEq>::eq(move _5, move _7) -> [return: bb3, unwind: bb5]; + } + + bb3: { + StorageDead(_7); + StorageDead(_5); + StorageDead(_8); + StorageDead(_4); + unreachable; + } + + bb4: { + return; + } + + bb5 (cleanup): { + resume; + } +} diff --git a/tests/mir-opt/building/eq_never_type.rs b/tests/mir-opt/building/eq_never_type.rs new file mode 100644 index 0000000000000..90e2e69753531 --- /dev/null +++ b/tests/mir-opt/building/eq_never_type.rs @@ -0,0 +1,13 @@ +// skip-filecheck +#![feature(never_type)] +#![allow(unreachable_code)] + +// EMIT_MIR eq_never_type._f.built.after.mir +fn _f(a: !, b: !) { + // Both arguments must be references (i.e. == should auto-borrow/coerce-to-ref both arguments) + // (this previously was buggy due to `NeverToAny` coercion incorrectly throwing out other + // coercions) + a == b; +} + +fn main() {} diff --git a/tests/ui/never_type/eq-never-types.rs b/tests/ui/never_type/eq-never-types.rs new file mode 100644 index 0000000000000..19717fcf4433c --- /dev/null +++ b/tests/ui/never_type/eq-never-types.rs @@ -0,0 +1,13 @@ +//@ check-pass +// +// issue: rust-lang/rust#120600 + +#![allow(internal_features)] +#![feature(never_type, rustc_attrs)] +#![rustc_never_type_options(fallback = "never")] + +fn ice(a: !) { + a == a; +} + +fn main() {}