Rollup merge of #136235 - oli-obk:transmuty-pat-tys, r=RalfJung

Pretty print pattern type values with transmute if they don't satisfy their pattern

Instead of printing `0_u32 is 1..`, we now print the default fallback rendering that we also use for invalid bools, chars, ...: `{transmute(0x00000000): (u32) is 1..=}`.

These cases can occur in mir dumps when const prop propagates a constant across a safety check that would prevent the actually UB value from existing. That's fine though, as it's dead code and we always need to allow UB in dead code.

follow-up to https://github.com/rust-lang/rust/pull/136176

cc ``@compiler-errors`` ``@scottmcm``

r? ``@RalfJung`` because of the interpreter changes

2 files changed, 5 insertions, 1 deletions

diff --git a/compiler/rustc_middle/src/hooks/mod.rs b/compiler/rustc_middle/src/hooks/mod.rs
index 276a02b4e0f..c5ce6efcb81 100644
--- a/compiler/rustc_middle/src/hooks/mod.rs
+++ b/compiler/rustc_middle/src/hooks/mod.rs
@@ -98,6 +98,10 @@ declare_hooks! {
     hook save_dep_graph() -> ();
 
     hook query_key_hash_verify_all() -> ();
+
+    /// Ensure the given scalar is valid for the given type.
+    /// This checks non-recursive runtime validity.
+    hook validate_scalar_in_layout(scalar: crate::ty::ScalarInt, ty: Ty<'tcx>) -> bool;
 }
 
 #[cold]
diff --git a/compiler/rustc_middle/src/ty/print/pretty.rs b/compiler/rustc_middle/src/ty/print/pretty.rs
index 3431081b189..feae8ea312e 100644
--- a/compiler/rustc_middle/src/ty/print/pretty.rs
+++ b/compiler/rustc_middle/src/ty/print/pretty.rs
@@ -1741,7 +1741,7 @@ pub trait PrettyPrinter<'tcx>: Printer<'tcx> + fmt::Write {
                     " as ",
                 )?;
             }
-            ty::Pat(base_ty, pat) => {
+            ty::Pat(base_ty, pat) if self.tcx().validate_scalar_in_layout(int, ty) => {
                 self.pretty_print_const_scalar_int(int, *base_ty, print_ty)?;
                 p!(write(" is {pat:?}"));
             }