Auto merge of #69257 - RalfJung:layout-visitor, r=eddyb

Adjust Miri value visitor, and doc-comment layout components

I realized that I still didn't have quite the right intuition for how our `LayoutDetails` work, so I had to adjust the Miri value visitor to the things I understood better now. I also added some doc-comments to `LayoutDetails` as a hopefully canonical place to note such things.

The main visitor change is that we *first* look at all the fields (according to `FieldPlacement`), and *then* check the variants and handle `Multiple` appropriately. I did not quite realize how orthogonal "fields" and "variants" are.
I also moved the check for the scalar ABI to *after* checking all the fields; this leads to better (more type-driven) error messages.

And it looks like we can finally remove that magic hack for `ty::Generator`. :D

r? @oli-obk for the Miri/visitor changes and @eddyb for the layout docs
The Miri PR is at: https://github.com/rust-lang/miri/pull/1178

11 files changed, 28 insertions, 28 deletions

diff --git a/src/test/ui/consts/const-eval/transmute-const.stderr b/src/test/ui/consts/const-eval/transmute-const.stderr
index 47f89fccf7a..e93a6887ba8 100644
--- a/src/test/ui/consts/const-eval/transmute-const.stderr
+++ b/src/test/ui/consts/const-eval/transmute-const.stderr
@@ -2,7 +2,7 @@ error[E0080]: it is undefined behavior to use this value
   --> $DIR/transmute-const.rs:5:1
    |
 LL | static FOO: bool = unsafe { mem::transmute(3u8) };
-   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ type validation failed: encountered 3, but expected something less or equal to 1
+   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ type validation failed: encountered 3, but expected a boolean
    |
    = note: The rules on what exactly is undefined behavior aren't clear, so this check might be overzealous. Please open an issue on the rustc repository if you believe it should not be considered undefined behavior.
 
diff --git a/src/test/ui/consts/const-eval/ub-enum.stderr b/src/test/ui/consts/const-eval/ub-enum.stderr
index 8ebc9dbec8a..8c47d68e968 100644
--- a/src/test/ui/consts/const-eval/ub-enum.stderr
+++ b/src/test/ui/consts/const-eval/ub-enum.stderr
@@ -10,7 +10,7 @@ error[E0080]: it is undefined behavior to use this value
   --> $DIR/ub-enum.rs:26:1
    |
 LL | const BAD_ENUM_PTR: Enum = unsafe { TransmuteEnum { in1: &1 }.out1 };
-   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ type validation failed: encountered a pointer, but expected a valid enum discriminant
+   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ type validation failed: encountered a pointer at .<enum-tag>, but expected initialized plain (non-pointer) bytes
    |
    = note: The rules on what exactly is undefined behavior aren't clear, so this check might be overzealous. Please open an issue on the rustc repository if you believe it should not be considered undefined behavior.
 
@@ -18,7 +18,7 @@ error[E0080]: it is undefined behavior to use this value
   --> $DIR/ub-enum.rs:29:1
    |
 LL | const BAD_ENUM_WRAPPED: Wrap<Enum> = unsafe { TransmuteEnum { in1: &1 }.out2 };
-   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ type validation failed: encountered a pointer, but expected something that cannot possibly fail to be equal to 0
+   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ type validation failed: encountered a pointer at .0.<enum-tag>, but expected initialized plain (non-pointer) bytes
    |
    = note: The rules on what exactly is undefined behavior aren't clear, so this check might be overzealous. Please open an issue on the rustc repository if you believe it should not be considered undefined behavior.
 
@@ -34,7 +34,7 @@ error[E0080]: it is undefined behavior to use this value
   --> $DIR/ub-enum.rs:50:1
    |
 LL | const BAD_ENUM2_PTR: Enum2 = unsafe { TransmuteEnum2 { in2: &0 }.out1 };
-   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ type validation failed: encountered a pointer, but expected a valid enum discriminant
+   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ type validation failed: encountered a pointer at .<enum-tag>, but expected initialized plain (non-pointer) bytes
    |
    = note: The rules on what exactly is undefined behavior aren't clear, so this check might be overzealous. Please open an issue on the rustc repository if you believe it should not be considered undefined behavior.
 
@@ -42,7 +42,7 @@ error[E0080]: it is undefined behavior to use this value
   --> $DIR/ub-enum.rs:52:1
    |
 LL | const BAD_ENUM2_WRAPPED: Wrap<Enum2> = unsafe { TransmuteEnum2 { in2: &0 }.out2 };
-   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ type validation failed: encountered a pointer, but expected something that cannot possibly fail to be equal to 2
+   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ type validation failed: encountered a pointer at .0.<enum-tag>, but expected initialized plain (non-pointer) bytes
    |
    = note: The rules on what exactly is undefined behavior aren't clear, so this check might be overzealous. Please open an issue on the rustc repository if you believe it should not be considered undefined behavior.
 
@@ -50,7 +50,7 @@ error[E0080]: it is undefined behavior to use this value
   --> $DIR/ub-enum.rs:56:1
    |
 LL | const BAD_ENUM2_UNDEF : Enum2 = unsafe { TransmuteEnum2 { in3: () }.out1 };
-   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ type validation failed: encountered uninitialized bytes, but expected a valid enum discriminant
+   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ type validation failed: encountered uninitialized bytes at .<enum-tag>, but expected initialized plain (non-pointer) bytes
    |
    = note: The rules on what exactly is undefined behavior aren't clear, so this check might be overzealous. Please open an issue on the rustc repository if you believe it should not be considered undefined behavior.
 
@@ -58,7 +58,7 @@ error[E0080]: it is undefined behavior to use this value
   --> $DIR/ub-enum.rs:60:1
    |
 LL | const BAD_ENUM2_OPTION_PTR: Option<Enum2> = unsafe { TransmuteEnum2 { in2: &0 }.out3 };
-   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ type validation failed: encountered a pointer, but expected a valid enum discriminant
+   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ type validation failed: encountered a pointer at .<enum-tag>, but expected initialized plain (non-pointer) bytes
    |
    = note: The rules on what exactly is undefined behavior aren't clear, so this check might be overzealous. Please open an issue on the rustc repository if you believe it should not be considered undefined behavior.
 
@@ -66,7 +66,7 @@ error[E0080]: it is undefined behavior to use this value
   --> $DIR/ub-enum.rs:71:1
    |
 LL | const BAD_OPTION_CHAR: Option<(char, char)> = Some(('x', unsafe { TransmuteChar { a: !0 }.b }));
-   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ type validation failed: encountered 4294967295 at .<downcast-variant(Some)>.0.1, but expected something less or equal to 1114111
+   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ type validation failed: encountered 4294967295 at .<enum-variant(Some)>.0.1, but expected a valid unicode codepoint
    |
    = note: The rules on what exactly is undefined behavior aren't clear, so this check might be overzealous. Please open an issue on the rustc repository if you believe it should not be considered undefined behavior.
 
diff --git a/src/test/ui/consts/const-eval/ub-nonnull.stderr b/src/test/ui/consts/const-eval/ub-nonnull.stderr
index 4d9d258f808..ec056187057 100644
--- a/src/test/ui/consts/const-eval/ub-nonnull.stderr
+++ b/src/test/ui/consts/const-eval/ub-nonnull.stderr
@@ -44,7 +44,7 @@ error[E0080]: it is undefined behavior to use this value
   --> $DIR/ub-nonnull.rs:32:1
    |
 LL | const UNINIT: NonZeroU8 = unsafe { Transmute { uninit: () }.out };
-   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ type validation failed: encountered uninitialized bytes, but expected something greater or equal to 1
+   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ type validation failed: encountered uninitialized bytes at .0, but expected initialized plain (non-pointer) bytes
    |
    = note: The rules on what exactly is undefined behavior aren't clear, so this check might be overzealous. Please open an issue on the rustc repository if you believe it should not be considered undefined behavior.
 
diff --git a/src/test/ui/consts/const-eval/ub-ref.rs b/src/test/ui/consts/const-eval/ub-ref.rs
index 03ac12c8b1a..889579ca1ec 100644
--- a/src/test/ui/consts/const-eval/ub-ref.rs
+++ b/src/test/ui/consts/const-eval/ub-ref.rs
@@ -6,7 +6,7 @@ use std::mem;
 
 const UNALIGNED: &u16 = unsafe { mem::transmute(&[0u8; 4]) };
 //~^ ERROR it is undefined behavior to use this value
-//~^^ type validation failed: encountered unaligned reference (required 2 byte alignment but found 1)
+//~^^ type validation failed: encountered an unaligned reference (required 2 byte alignment but found 1)
 
 const NULL: &u16 = unsafe { mem::transmute(0usize) };
 //~^ ERROR it is undefined behavior to use this value
diff --git a/src/test/ui/consts/const-eval/ub-ref.stderr b/src/test/ui/consts/const-eval/ub-ref.stderr
index 01bde413c0d..5cef0a488eb 100644
--- a/src/test/ui/consts/const-eval/ub-ref.stderr
+++ b/src/test/ui/consts/const-eval/ub-ref.stderr
@@ -2,7 +2,7 @@ error[E0080]: it is undefined behavior to use this value
   --> $DIR/ub-ref.rs:7:1
    |
 LL | const UNALIGNED: &u16 = unsafe { mem::transmute(&[0u8; 4]) };
-   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ type validation failed: encountered unaligned reference (required 2 byte alignment but found 1)
+   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ type validation failed: encountered an unaligned reference (required 2 byte alignment but found 1)
    |
    = note: The rules on what exactly is undefined behavior aren't clear, so this check might be overzealous. Please open an issue on the rustc repository if you believe it should not be considered undefined behavior.
 
@@ -10,7 +10,7 @@ error[E0080]: it is undefined behavior to use this value
   --> $DIR/ub-ref.rs:11:1
    |
 LL | const NULL: &u16 = unsafe { mem::transmute(0usize) };
-   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ type validation failed: encountered 0, but expected something greater or equal to 1
+   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ type validation failed: encountered a NULL reference
    |
    = note: The rules on what exactly is undefined behavior aren't clear, so this check might be overzealous. Please open an issue on the rustc repository if you believe it should not be considered undefined behavior.
 
@@ -34,7 +34,7 @@ error[E0080]: it is undefined behavior to use this value
   --> $DIR/ub-ref.rs:23:1
    |
 LL | const USIZE_AS_REF: &'static u8 = unsafe { mem::transmute(1337usize) };
-   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ type validation failed: encountered dangling reference (created from integer)
+   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ type validation failed: encountered a dangling reference (created from integer)
    |
    = note: The rules on what exactly is undefined behavior aren't clear, so this check might be overzealous. Please open an issue on the rustc repository if you believe it should not be considered undefined behavior.
 
diff --git a/src/test/ui/consts/const-eval/ub-uninhabit.stderr b/src/test/ui/consts/const-eval/ub-uninhabit.stderr
index 3877f3cab6d..4fef9aa84ea 100644
--- a/src/test/ui/consts/const-eval/ub-uninhabit.stderr
+++ b/src/test/ui/consts/const-eval/ub-uninhabit.stderr
@@ -2,7 +2,7 @@ error[E0080]: it is undefined behavior to use this value
   --> $DIR/ub-uninhabit.rs:15:1
    |
 LL | const BAD_BAD_BAD: Bar = unsafe { (TransmuteUnion::<(), Bar> { a: () }).b };
-   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ type validation failed: encountered a value of an uninhabited type
+   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ type validation failed: encountered a value of uninhabited type Bar
    |
    = note: The rules on what exactly is undefined behavior aren't clear, so this check might be overzealous. Please open an issue on the rustc repository if you believe it should not be considered undefined behavior.
 
@@ -10,7 +10,7 @@ error[E0080]: it is undefined behavior to use this value
   --> $DIR/ub-uninhabit.rs:18:1
    |
 LL | const BAD_BAD_REF: &Bar = unsafe { mem::transmute(1usize) };
-   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ type validation failed: encountered a value of an uninhabited type at .<deref>
+   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ type validation failed: encountered a value of uninhabited type Bar at .<deref>
    |
    = note: The rules on what exactly is undefined behavior aren't clear, so this check might be overzealous. Please open an issue on the rustc repository if you believe it should not be considered undefined behavior.
 
@@ -18,7 +18,7 @@ error[E0080]: it is undefined behavior to use this value
   --> $DIR/ub-uninhabit.rs:21:1
    |
 LL | const BAD_BAD_ARRAY: [Bar; 1] = unsafe { (TransmuteUnion::<(), [Bar; 1]> { a: () }).b };
-   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ type validation failed: encountered a value of an uninhabited type
+   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ type validation failed: encountered a value of uninhabited type [Bar; 1]
    |
    = note: The rules on what exactly is undefined behavior aren't clear, so this check might be overzealous. Please open an issue on the rustc repository if you believe it should not be considered undefined behavior.
 
diff --git a/src/test/ui/consts/const-eval/ub-upvars.stderr b/src/test/ui/consts/const-eval/ub-upvars.stderr
index ea6ab3ae5b5..972c9eb38c8 100644
--- a/src/test/ui/consts/const-eval/ub-upvars.stderr
+++ b/src/test/ui/consts/const-eval/ub-upvars.stderr
@@ -6,7 +6,7 @@ LL | |     let bad_ref: &'static u16 = unsafe { mem::transmute(0usize) };
 LL | |     let another_var = 13;
 LL | |     move || { let _ = bad_ref; let _ = another_var; }
 LL | | };
-   | |__^ type validation failed: encountered 0 at .<deref>.<dyn-downcast>.<closure-var(bad_ref)>, but expected something greater or equal to 1
+   | |__^ type validation failed: encountered a NULL reference at .<deref>.<dyn-downcast>.<captured-var(bad_ref)>
    |
    = note: The rules on what exactly is undefined behavior aren't clear, so this check might be overzealous. Please open an issue on the rustc repository if you believe it should not be considered undefined behavior.
 
diff --git a/src/test/ui/consts/const-eval/ub-wide-ptr.stderr b/src/test/ui/consts/const-eval/ub-wide-ptr.stderr
index ce57d680dc9..4da9ad6c332 100644
--- a/src/test/ui/consts/const-eval/ub-wide-ptr.stderr
+++ b/src/test/ui/consts/const-eval/ub-wide-ptr.stderr
@@ -2,7 +2,7 @@ error[E0080]: it is undefined behavior to use this value
   --> $DIR/ub-wide-ptr.rs:86:1
    |
 LL | const STR_TOO_LONG: &str = unsafe { SliceTransmute { repr: SliceRepr { ptr: &42, len: 999 } }.str};
-   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ type validation failed: encountered dangling reference (not entirely in bounds)
+   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ type validation failed: encountered a dangling reference (not entirely in bounds)
    |
    = note: The rules on what exactly is undefined behavior aren't clear, so this check might be overzealous. Please open an issue on the rustc repository if you believe it should not be considered undefined behavior.
 
@@ -50,7 +50,7 @@ error[E0080]: it is undefined behavior to use this value
   --> $DIR/ub-wide-ptr.rs:109:1
    |
 LL | const SLICE_TOO_LONG: &[u8] = unsafe { SliceTransmute { repr: SliceRepr { ptr: &42, len: 999 } }.slice};
-   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ type validation failed: encountered dangling reference (not entirely in bounds)
+   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ type validation failed: encountered a dangling reference (not entirely in bounds)
    |
    = note: The rules on what exactly is undefined behavior aren't clear, so this check might be overzealous. Please open an issue on the rustc repository if you believe it should not be considered undefined behavior.
 
@@ -66,7 +66,7 @@ error[E0080]: it is undefined behavior to use this value
   --> $DIR/ub-wide-ptr.rs:116:1
    |
 LL | const SLICE_CONTENT_INVALID: &[bool] = &[unsafe { BoolTransmute { val: 3 }.bl }];
-   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ type validation failed: encountered 3 at .<deref>[0], but expected something less or equal to 1
+   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ type validation failed: encountered 3 at .<deref>[0], but expected a boolean
    |
    = note: The rules on what exactly is undefined behavior aren't clear, so this check might be overzealous. Please open an issue on the rustc repository if you believe it should not be considered undefined behavior.
 
@@ -74,7 +74,7 @@ error[E0080]: it is undefined behavior to use this value
   --> $DIR/ub-wide-ptr.rs:122:1
    |
 LL | const MYSLICE_PREFIX_BAD: &MySliceBool = &MySlice(unsafe { BoolTransmute { val: 3 }.bl }, [false]);
-   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ type validation failed: encountered 3 at .<deref>.0, but expected something less or equal to 1
+   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ type validation failed: encountered 3 at .<deref>.0, but expected a boolean
    |
    = note: The rules on what exactly is undefined behavior aren't clear, so this check might be overzealous. Please open an issue on the rustc repository if you believe it should not be considered undefined behavior.
 
@@ -82,7 +82,7 @@ error[E0080]: it is undefined behavior to use this value
   --> $DIR/ub-wide-ptr.rs:125:1
    |
 LL | const MYSLICE_SUFFIX_BAD: &MySliceBool = &MySlice(true, [unsafe { BoolTransmute { val: 3 }.bl }]);
-   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ type validation failed: encountered 3 at .<deref>.1[0], but expected something less or equal to 1
+   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ type validation failed: encountered 3 at .<deref>.1[0], but expected a boolean
    |
    = note: The rules on what exactly is undefined behavior aren't clear, so this check might be overzealous. Please open an issue on the rustc repository if you believe it should not be considered undefined behavior.
 
@@ -122,7 +122,7 @@ error[E0080]: it is undefined behavior to use this value
   --> $DIR/ub-wide-ptr.rs:147:1
    |
 LL | const TRAIT_OBJ_CONTENT_INVALID: &dyn Trait = &unsafe { BoolTransmute { val: 3 }.bl };
-   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ type validation failed: encountered 3 at .<deref>.<dyn-downcast>, but expected something less or equal to 1
+   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ type validation failed: encountered 3 at .<deref>.<dyn-downcast>, but expected a boolean
    |
    = note: The rules on what exactly is undefined behavior aren't clear, so this check might be overzealous. Please open an issue on the rustc repository if you believe it should not be considered undefined behavior.
 
diff --git a/src/test/ui/consts/const-eval/union-ub.stderr b/src/test/ui/consts/const-eval/union-ub.stderr
index fa67bc0d8e7..9d90d6e8548 100644
--- a/src/test/ui/consts/const-eval/union-ub.stderr
+++ b/src/test/ui/consts/const-eval/union-ub.stderr
@@ -2,7 +2,7 @@ error[E0080]: it is undefined behavior to use this value
   --> $DIR/union-ub.rs:31:1
    |
 LL | const BAD_BOOL: bool = unsafe { DummyUnion { u8: 42 }.bool};
-   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ type validation failed: encountered 42, but expected something less or equal to 1
+   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ type validation failed: encountered 42, but expected a boolean
    |
    = note: The rules on what exactly is undefined behavior aren't clear, so this check might be overzealous. Please open an issue on the rustc repository if you believe it should not be considered undefined behavior.
 
diff --git a/src/test/ui/consts/const-eval/validate_uninhabited_zsts.stderr b/src/test/ui/consts/const-eval/validate_uninhabited_zsts.stderr
index c98e206e88c..2a338e27640 100644
--- a/src/test/ui/consts/const-eval/validate_uninhabited_zsts.stderr
+++ b/src/test/ui/consts/const-eval/validate_uninhabited_zsts.stderr
@@ -20,7 +20,7 @@ error[E0080]: it is undefined behavior to use this value
   --> $DIR/validate_uninhabited_zsts.rs:17:1
    |
 LL | const BAR: [Empty; 3] = [unsafe { std::mem::transmute(()) }; 3];
-   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ type validation failed: encountered a value of an uninhabited type
+   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ type validation failed: encountered a value of uninhabited type [Empty; 3]
    |
    = note: The rules on what exactly is undefined behavior aren't clear, so this check might be overzealous. Please open an issue on the rustc repository if you believe it should not be considered undefined behavior.
 
diff --git a/src/test/ui/consts/validate_never_arrays.stderr b/src/test/ui/consts/validate_never_arrays.stderr
index cb995b8216f..203620a771b 100644
--- a/src/test/ui/consts/validate_never_arrays.stderr
+++ b/src/test/ui/consts/validate_never_arrays.stderr
@@ -2,7 +2,7 @@ error[E0080]: it is undefined behavior to use this value
   --> $DIR/validate_never_arrays.rs:3:1
    |
 LL | const _: &[!; 1] = unsafe { &*(1_usize as *const [!; 1]) };
-   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ type validation failed: encountered a value of an uninhabited type at .<deref>
+   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ type validation failed: encountered a value of uninhabited type [!; 1] at .<deref>
    |
    = note: The rules on what exactly is undefined behavior aren't clear, so this check might be overzealous. Please open an issue on the rustc repository if you believe it should not be considered undefined behavior.
 
@@ -10,7 +10,7 @@ error[E0080]: it is undefined behavior to use this value
   --> $DIR/validate_never_arrays.rs:6:1
    |
 LL | const _: &[!] = unsafe { &*(1_usize as *const [!; 1]) };
-   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ type validation failed: encountered a value of an uninhabited type at .<deref>[0]
+   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ type validation failed: encountered a value of uninhabited type ! at .<deref>[0]
    |
    = note: The rules on what exactly is undefined behavior aren't clear, so this check might be overzealous. Please open an issue on the rustc repository if you believe it should not be considered undefined behavior.
 
@@ -18,7 +18,7 @@ error[E0080]: it is undefined behavior to use this value
   --> $DIR/validate_never_arrays.rs:7:1
    |
 LL | const _: &[!] = unsafe { &*(1_usize as *const [!; 42]) };
-   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ type validation failed: encountered a value of an uninhabited type at .<deref>[0]
+   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ type validation failed: encountered a value of uninhabited type ! at .<deref>[0]
    |
    = note: The rules on what exactly is undefined behavior aren't clear, so this check might be overzealous. Please open an issue on the rustc repository if you believe it should not be considered undefined behavior.