Auto merge of #120313 - Nadrieril:graceful-error, r=compiler-errors

pattern_analysis: Gracefully abort on type incompatibility

This leaves the option for a consumer of the crate to return `Err` instead of panicking on type error. rust-analyzer could use that (e.g. https://github.com/rust-lang/rust-analyzer/issues/15808).

Since the only use of `TypeCx::bug` is in `Constructor::is_covered_by`, it is tempting to return `false` instead of `Err()`, but that would cause "non-exhaustive match" false positives.

r? `@compiler-errors`

compiler/rustc_pattern_analysis/src/rustc.rs

@@ -901,7 +901,7 @@ impl<'p, 'tcx> TypeCx for RustcMatchCheckCtxt<'p, 'tcx> {
         Ok(())
     }
 
-    fn bug(&self, fmt: fmt::Arguments<'_>) -> ! {
+    fn bug(&self, fmt: fmt::Arguments<'_>) -> Self::Error {
         span_bug!(self.scrut_span, "{}", fmt)
     }