Rollup merge of #131112 - jswrenn:fix-130413, r=compiler-errors

TransmuteFrom: Gracefully handle unnormalized types and normalization errors
~~Refactor to share code between `TransmuteFrom`'s trait selection and error reporting code paths. Additionally normalizes the source and destination types, and gracefully handles normalization errors.~~
Fixes#130413
r​? `@compiler-errors`

Author: matthiaskrgr

compiler/rustc_trait_selection/src/error_reporting/traits/fulfillment_errors.rs

@@ -245,6 +245,9 @@ impl<'a, 'tcx> TypeErrCtxt<'a, 'tcx> {
  span,"silent safe transmute error"
 );
 }
+GetSafeTransmuteErrorAndReason::Default => {
+(err_msg,None)
+}
 GetSafeTransmuteErrorAndReason::Error{
  err_msg,
  safe_transmute_explanation,
@@ -2226,6 +2229,12 @@ impl<'a, 'tcx> TypeErrCtxt<'a, 'tcx> {
 ) -> GetSafeTransmuteErrorAndReason{
 use rustc_transmute::Answer;
 
+// We don't assemble a transmutability candidate for types that are generic
+// and we should have ambiguity for types that still have non-region infer.
+if obligation.predicate.has_non_region_param() || obligation.has_non_region_infer(){
+returnGetSafeTransmuteErrorAndReason::Default;
+}
+
 // Erase regions because layout code doesn't particularly care about regions.
 let trait_ref =
 self.tcx.erase_regions(self.tcx.instantiate_bound_regions_with_erased(trait_ref));
@@ -2248,6 +2257,7 @@ impl<'a, 'tcx> TypeErrCtxt<'a, 'tcx> {
 
 let dst = trait_ref.args.type_at(0);
 let src = trait_ref.args.type_at(1);
+
 let err_msg = format!("`{src}` cannot be safely transmuted into `{dst}`");
 
 match rustc_transmute::TransmuteTypeEnv::new(self.infcx).is_transmutable(

compiler/rustc_trait_selection/src/error_reporting/traits/mod.rs

@@ -43,6 +43,7 @@ pub struct ImplCandidate<'tcx> {
 
 enumGetSafeTransmuteErrorAndReason{
 Silent,
+Default,
 Error{err_msg:String,safe_transmute_explanation:Option<String>},
 }
 

compiler/rustc_transmute/src/layout/tree.rs

@@ -195,10 +195,11 @@ pub(crate) mod rustc {
 impl<'tcx>From<&LayoutError<'tcx>>forErr{
 fnfrom(err:&LayoutError<'tcx>) -> Self{
 match err {
-LayoutError::Unknown(..) | LayoutError::ReferencesError(..) => Self::UnknownLayout,
+LayoutError::Unknown(..)
+ | LayoutError::ReferencesError(..)
+ | LayoutError::NormalizationFailure(..) => Self::UnknownLayout,
 LayoutError::SizeOverflow(..) => Self::SizeOverflow,
 LayoutError::Cycle(err) => Self::TypeError(*err),
- err => unimplemented!("{:?}", err),
 }
 }
 }

tests/crashes/125881.rs

@@ -0,0 +1,25 @@
+#![crate_type = "lib"]
+#![feature(transmutability)]
+
+traitA{
+typeAssocA;
+}
+
+traitB{
+typeAssocB: std::mem::TransmuteFrom<()>;
+}
+
+impl<T>Bfor(T,u8)
+where
+T:A,
+{
+typeAssocB = T::AssocA;//~ERROR: the trait bound `<T as A>::AssocA: TransmuteFrom<(), Assume { alignment: false, lifetimes: false, safety: false, validity: false }>` is not satisfied [E0277]
+}
+
+
+impl<T>Bfor(T,u16)
+where
+for<'a>&'ai32:A,
+{
+typeAssocB = <&'statici32asA>::AssocA;//~ERROR: `()` cannot be safely transmuted into `<&i32 as A>::AssocA`
+}

tests/crashes/126377.rs

@@ -0,0 +1,31 @@
+error[E0277]: the trait bound `<T as A>::AssocA: TransmuteFrom<(), Assume { alignment: false, lifetimes: false, safety: false, validity: false }>` is not satisfied
+ --> $DIR/assoc-bound.rs:16:19
+ |
+LL | type AssocB = T::AssocA;
+ | ^^^^^^^^^ the trait `TransmuteFrom<(), Assume { alignment: false, lifetimes: false, safety: false, validity: false }>` is not implemented for `<T as A>::AssocA`
+ |
+note: required by a bound in `B::AssocB`
+ --> $DIR/assoc-bound.rs:9:18
+ |
+LL | type AssocB: std::mem::TransmuteFrom<()>;
+ | ^^^^^^^^^^^^^^^^^^^^^^^^^^^ required by this bound in `B::AssocB`
+help: consider further restricting the associated type
+ |
+LL | T: A, <T as A>::AssocA: TransmuteFrom<(), Assume { alignment: false, lifetimes: false, safety: false, validity: false }>
+ | ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+error[E0277]: `()` cannot be safely transmuted into `<&i32 as A>::AssocA`
+ --> $DIR/assoc-bound.rs:24:19
+ |
+LL | type AssocB = <&'static i32 as A>::AssocA;
+ | ^^^^^^^^^^^^^^^^^^^^^^^^^^^ `<&i32 as A>::AssocA` has an unknown layout
+ |
+note: required by a bound in `B::AssocB`
+ --> $DIR/assoc-bound.rs:9:18
+ |
+LL | type AssocB: std::mem::TransmuteFrom<()>;
+ | ^^^^^^^^^^^^^^^^^^^^^^^^^^^ required by this bound in `B::AssocB`
+
+error: aborting due to 2 previous errors
+
+For more information about this error, try `rustc --explain E0277`.