Rollup merge of #112810 - compiler-errors:dont-ice-on-bad-layout, r=wesleywiser

Don't ICE on unnormalized struct tail in layout computation

1. We try to compute a `SizeSkeleton` even if a layout error occurs, but we really only need to do this if we get `LayoutError::Unknown`, since that means our type is too polymorphic to actually compute the full layout. If we have other errors, like `LayoutError::NormalizationError` or `LayoutError::Cycle`, then we can't really make any progress, since this represents an actual error.
2. Avoid using `normalize_erasing_regions` and `struct_tail_erasing_lifetimes` since those ICE on normalization errors, and since we may call `layout_of` in HIR typeck, we don't know for certain that we're on the happy path.

Fixes #112736

4 files changed, 45 insertions, 4 deletions

diff --git a/tests/ui/const-generics/issue-112505-overflow.stderr b/tests/ui/const-generics/issue-112505-overflow.stderr
index 0432f2fa8be..bd8a4feeff5 100644
--- a/tests/ui/const-generics/issue-112505-overflow.stderr
+++ b/tests/ui/const-generics/issue-112505-overflow.stderr
@@ -4,8 +4,8 @@ error[E0512]: cannot transmute between types of different sizes, or dependently-
 LL |     unsafe { std::mem::transmute(v) }
    |              ^^^^^^^^^^^^^^^^^^^
    |
-   = note: source type: `[[[u32; 8888888]; 9999999]; 777777777]` (values of the type `[[[u32; 8888888]; 9999999]; 777777777]` are too big for the current architecture)
-   = note: target type: `[[[u32; 9999999]; 777777777]; 239]` (59484438436515561504 bits)
+   = note: source type: `[[[u32; 8888888]; 9999999]; 777777777]` (values of the type `[[u32; 8888888]; 9999999]` are too big for the current architecture)
+   = note: target type: `[[[u32; 9999999]; 777777777]; 239]` (values of the type `[[u32; 9999999]; 777777777]` are too big for the current architecture)
 
 error: aborting due to previous error
 
diff --git a/tests/ui/const-generics/transmute-fail.stderr b/tests/ui/const-generics/transmute-fail.stderr
index 3d1197afd0f..9e308620a9c 100644
--- a/tests/ui/const-generics/transmute-fail.stderr
+++ b/tests/ui/const-generics/transmute-fail.stderr
@@ -43,8 +43,8 @@ error[E0512]: cannot transmute between types of different sizes, or dependently-
 LL |     std::mem::transmute(v)
    |     ^^^^^^^^^^^^^^^^^^^
    |
-   = note: source type: `[[[u32; 8888888]; 9999999]; 777777777]` (values of the type `[[[u32; 8888888]; 9999999]; 777777777]` are too big for the current architecture)
-   = note: target type: `[[[u32; 9999999]; 777777777]; 8888888]` (values of the type `[[[u32; 9999999]; 777777777]; 8888888]` are too big for the current architecture)
+   = note: source type: `[[[u32; 8888888]; 9999999]; 777777777]` (values of the type `[[u32; 8888888]; 9999999]` are too big for the current architecture)
+   = note: target type: `[[[u32; 9999999]; 777777777]; 8888888]` (values of the type `[[u32; 9999999]; 777777777]` are too big for the current architecture)
 
 error: aborting due to 6 previous errors
 
diff --git a/tests/ui/layout/cannot-transmute-unnormalizable-type.rs b/tests/ui/layout/cannot-transmute-unnormalizable-type.rs
new file mode 100644
index 00000000000..d2b6e1d8eba
--- /dev/null
+++ b/tests/ui/layout/cannot-transmute-unnormalizable-type.rs
@@ -0,0 +1,22 @@
+trait Trait {
+    type RefTarget;
+}
+
+impl Trait for ()
+where
+    Missing: Trait,
+    //~^ ERROR cannot find type `Missing` in this scope
+{
+    type RefTarget = ();
+}
+
+struct Other {
+    data: <() as Trait>::RefTarget,
+}
+
+fn main() {
+    unsafe {
+        std::mem::transmute::<Option<()>, Option<&Other>>(None);
+        //~^ ERROR cannot transmute between types of different sizes, or dependently-sized types
+    }
+}
diff --git a/tests/ui/layout/cannot-transmute-unnormalizable-type.stderr b/tests/ui/layout/cannot-transmute-unnormalizable-type.stderr
new file mode 100644
index 00000000000..dd5119318ff
--- /dev/null
+++ b/tests/ui/layout/cannot-transmute-unnormalizable-type.stderr
@@ -0,0 +1,19 @@
+error[E0412]: cannot find type `Missing` in this scope
+  --> $DIR/cannot-transmute-unnormalizable-type.rs:7:5
+   |
+LL |     Missing: Trait,
+   |     ^^^^^^^ not found in this scope
+
+error[E0512]: cannot transmute between types of different sizes, or dependently-sized types
+  --> $DIR/cannot-transmute-unnormalizable-type.rs:19:9
+   |
+LL |         std::mem::transmute::<Option<()>, Option<&Other>>(None);
+   |         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+   |
+   = note: source type: `Option<()>` (8 bits)
+   = note: target type: `Option<&Other>` (unable to determine layout for `Other` because `<() as Trait>::RefTarget` cannot be normalized)
+
+error: aborting due to 2 previous errors
+
+Some errors have detailed explanations: E0412, E0512.
+For more information about an error, try `rustc --explain E0412`.