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Use resolved types in body of coerce_unsized

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Aaron Hill 2020-02-28 14:07:51 -05:00
parent 32c360b993
commit ff6e4ee7ad
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1 changed files with 7 additions and 3 deletions
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10
src/librustc_typeck/check/coercion.rs
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@ -452,9 +452,13 @@ impl<'f, 'tcx> Coerce<'f, 'tcx> {
// &[T; n] or &mut [T; n] -> &[T]
// or &mut [T; n] -> &mut [T]
// or &Concrete -> &Trait, etc.
fn coerce_unsized(&self, source: Ty<'tcx>, target: Ty<'tcx>) -> CoerceResult<'tcx> {
fn coerce_unsized(&self, mut source: Ty<'tcx>, mut target: Ty<'tcx>) -> CoerceResult<'tcx> {
debug!("coerce_unsized(source={:?}, target={:?})", source, target);
source = self.shallow_resolve(source);
target = self.shallow_resolve(target);
debug!("coerce_unsized: resolved source={:?} target={:?}", source, target);
// These 'if' statements require some explanation.
// The `CoerceUnsized` trait is special - it is only
// possible to write `impl CoerceUnsized<B> for A` where
@ -476,11 +480,11 @@ impl<'f, 'tcx> Coerce<'f, 'tcx> {
// the compiler! Therefore, we can be sure that coercion will always fail
// when either the source or target type is a type variable. This allows us
// to skip performing any trait selection, and immediately bail out.
if self.shallow_resolve(source).is_ty_var() {
if source.is_ty_var() {
debug!("coerce_unsized: source is a TyVar, bailing out");
return Err(TypeError::Mismatch);
}
if self.shallow_resolve(target).is_ty_var() {
if target.is_ty_var() {
debug!("coerce_unsized: target is a TyVar, bailing out");
return Err(TypeError::Mismatch);
}