Add allocation information to undefined behaviour errors.

compiler/rustc_mir/src/const_eval/eval_queries.rs

@@ -5,6 +5,7 @@ use crate::interpret::{
     Immediate, InternKind, InterpCx, InterpResult, MPlaceTy, MemoryKind, OpTy, RefTracking, Scalar,
     ScalarMaybeUninit, StackPopCleanup,
 };
+use crate::util::pretty::display_allocation;
 
 use rustc_errors::ErrorReported;
 use rustc_hir::def::DefKind;
@@ -360,6 +361,15 @@ pub fn eval_to_allocation_raw_provider<'tcx>(
                     "it is undefined behavior to use this value",
                     |mut diag| {
                         diag.note(note_on_undefined_behavior_error());
+                        diag.note(&format!(
+                            "the raw bytes of the constant ({}",
+                            display_allocation(
+                                *ecx.tcx,
+                                ecx.tcx
+                                    .global_alloc(mplace.ptr.assert_ptr().alloc_id)
+                                    .unwrap_memory()
+                            )
+                        ));
                         diag.emit();
                     },
                 ))

src/test/ui/const-generics/min_const_generics/invalid-patterns.stderr → src/test/ui/const-generics/min_const_generics/invalid-patterns.32bit.stderr

@@ -1,58 +1,70 @@
 error[E0308]: mismatched types
-  --> $DIR/invalid-patterns.rs:28:21
+  --> $DIR/invalid-patterns.rs:29:21
    |
 LL |   get_flag::<false, 0xFF>();
    |                     ^^^^ expected `char`, found `u8`
 
 error[E0308]: mismatched types
-  --> $DIR/invalid-patterns.rs:30:14
+  --> $DIR/invalid-patterns.rs:31:14
    |
 LL |   get_flag::<7, 'c'>();
    |              ^ expected `bool`, found integer
 
 error[E0308]: mismatched types
-  --> $DIR/invalid-patterns.rs:32:14
+  --> $DIR/invalid-patterns.rs:33:14
    |
 LL |   get_flag::<42, 0x5ad>();
    |              ^^ expected `bool`, found integer
 
 error[E0308]: mismatched types
-  --> $DIR/invalid-patterns.rs:32:18
+  --> $DIR/invalid-patterns.rs:33:18
    |
 LL |   get_flag::<42, 0x5ad>();
    |                  ^^^^^ expected `char`, found `u8`
 
 error[E0080]: it is undefined behavior to use this value
-  --> $DIR/invalid-patterns.rs:37:21
+  --> $DIR/invalid-patterns.rs:38:21
    |
 LL |   get_flag::<false, { unsafe { char_raw.character } }>();
    |                     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ type validation failed: encountered uninitialized bytes, but expected a valid unicode scalar value (in `0..=0x10FFFF` but not in `0xD800..=0xDFFF`)
    |
    = 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.
+   = note: the raw bytes of the constant (size: 4, align: 4) {
+               __ __ __ __                                     │ ░░░░
+           }
 
 error[E0080]: it is undefined behavior to use this value
-  --> $DIR/invalid-patterns.rs:39:14
+  --> $DIR/invalid-patterns.rs:40:14
    |
 LL |   get_flag::<{ unsafe { bool_raw.boolean } }, 'z'>();
    |              ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ type validation failed: encountered 0x42, 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.
+   = note: the raw bytes of the constant (size: 1, align: 1) {
+               42                                              │ B
+           }
 
 error[E0080]: it is undefined behavior to use this value
-  --> $DIR/invalid-patterns.rs:41:14
+  --> $DIR/invalid-patterns.rs:42:14
    |
 LL |   get_flag::<{ unsafe { bool_raw.boolean } }, { unsafe { char_raw.character } }>();
    |              ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ type validation failed: encountered 0x42, 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.
+   = note: the raw bytes of the constant (size: 1, align: 1) {
+               42                                              │ B
+           }
 
 error[E0080]: it is undefined behavior to use this value
-  --> $DIR/invalid-patterns.rs:41:47
+  --> $DIR/invalid-patterns.rs:42:47
    |
 LL |   get_flag::<{ unsafe { bool_raw.boolean } }, { unsafe { char_raw.character } }>();
    |                                               ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ type validation failed: encountered uninitialized bytes, but expected a valid unicode scalar value (in `0..=0x10FFFF` but not in `0xD800..=0xDFFF`)
    |
    = 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.
+   = note: the raw bytes of the constant (size: 4, align: 4) {
+               __ __ __ __                                     │ ░░░░
+           }
 
 error: aborting due to 8 previous errors
 

src/test/ui/const-generics/min_const_generics/invalid-patterns.64bit.stderr

@@ -0,0 +1,72 @@
+error[E0308]: mismatched types
+  --> $DIR/invalid-patterns.rs:29:21
+   |
+LL |   get_flag::<false, 0xFF>();
+   |                     ^^^^ expected `char`, found `u8`
+
+error[E0308]: mismatched types
+  --> $DIR/invalid-patterns.rs:31:14
+   |
+LL |   get_flag::<7, 'c'>();
+   |              ^ expected `bool`, found integer
+
+error[E0308]: mismatched types
+  --> $DIR/invalid-patterns.rs:33:14
+   |
+LL |   get_flag::<42, 0x5ad>();
+   |              ^^ expected `bool`, found integer
+
+error[E0308]: mismatched types
+  --> $DIR/invalid-patterns.rs:33:18
+   |
+LL |   get_flag::<42, 0x5ad>();
+   |                  ^^^^^ expected `char`, found `u8`
+
+error[E0080]: it is undefined behavior to use this value
+  --> $DIR/invalid-patterns.rs:38:21
+   |
+LL |   get_flag::<false, { unsafe { char_raw.character } }>();
+   |                     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ type validation failed: encountered uninitialized bytes, but expected a valid unicode scalar value (in `0..=0x10FFFF` but not in `0xD800..=0xDFFF`)
+   |
+   = 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.
+   = note: the raw bytes of the constant (size: 4, align: 4) {
+               __ __ __ __                                     │ ░░░░
+           }
+
+error[E0080]: it is undefined behavior to use this value
+  --> $DIR/invalid-patterns.rs:40:14
+   |
+LL |   get_flag::<{ unsafe { bool_raw.boolean } }, 'z'>();
+   |              ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ type validation failed: encountered 0x42, 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.
+   = note: the raw bytes of the constant (size: 1, align: 1) {
+               42                                              │ B
+           }
+
+error[E0080]: it is undefined behavior to use this value
+  --> $DIR/invalid-patterns.rs:42:14
+   |
+LL |   get_flag::<{ unsafe { bool_raw.boolean } }, { unsafe { char_raw.character } }>();
+   |              ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ type validation failed: encountered 0x42, 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.
+   = note: the raw bytes of the constant (size: 1, align: 1) {
+               42                                              │ B
+           }
+
+error[E0080]: it is undefined behavior to use this value
+  --> $DIR/invalid-patterns.rs:42:47
+   |
+LL |   get_flag::<{ unsafe { bool_raw.boolean } }, { unsafe { char_raw.character } }>();
+   |                                               ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ type validation failed: encountered uninitialized bytes, but expected a valid unicode scalar value (in `0..=0x10FFFF` but not in `0xD800..=0xDFFF`)
+   |
+   = 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.
+   = note: the raw bytes of the constant (size: 4, align: 4) {
+               __ __ __ __                                     │ ░░░░
+           }
+
+error: aborting due to 8 previous errors
+
+Some errors have detailed explanations: E0080, E0308.
+For more information about an error, try `rustc --explain E0080`.

src/test/ui/const-generics/min_const_generics/invalid-patterns.rs

@@ -1,3 +1,4 @@
+// stderr-per-bitwidth
 use std::mem::transmute;
 
 fn get_flag<const FlagSet: bool, const ShortName: char>() -> Option<char> {

src/test/ui/consts/const-err4.stderr → src/test/ui/consts/const-err4.32bit.stderr

@@ -1,10 +1,13 @@
 error[E0080]: it is undefined behavior to use this value
-  --> $DIR/const-err4.rs:8:11
+  --> $DIR/const-err4.rs:9:11
    |
 LL |     Boo = [unsafe { Foo { b: () }.a }; 4][3],
    |           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ type validation failed: encountered uninitialized bytes, 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.
+   = note: the raw bytes of the constant (size: 4, align: 4) {
+               __ __ __ __                                     │ ░░░░
+           }
 
 error: aborting due to previous error
 

src/test/ui/consts/const-err4.64bit.stderr

@@ -0,0 +1,14 @@
+error[E0080]: it is undefined behavior to use this value
+  --> $DIR/const-err4.rs:9:11
+   |
+LL |     Boo = [unsafe { Foo { b: () }.a }; 4][3],
+   |           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ type validation failed: encountered uninitialized bytes, 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.
+   = note: the raw bytes of the constant (size: 8, align: 8) {
+               __ __ __ __ __ __ __ __                         │ ░░░░░░░░
+           }
+
+error: aborting due to previous error
+
+For more information about this error, try `rustc --explain E0080`.

src/test/ui/consts/const-err4.rs

@@ -1,3 +1,4 @@
+// stderr-per-bitwidth
 #[derive(Copy, Clone)]
 union Foo {
     a: isize,