switch validation of scalars to be type-driven

This does not actually regress anything.  It would regress NonNull, but we
didn't handle that correctly previously either.

src/test/ui/consts/const-eval/const-pointer-values-in-various-types.stderr

@@ -2,7 +2,7 @@ error[E0080]: this constant likely exhibits undefined behavior
   --> $DIR/const-pointer-values-in-various-types.rs:24:5
    |
 LL |     const I32_REF_USIZE_UNION: usize = unsafe { Nonsense { int_32_ref: &3 }.u };
-   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ type validation failed: encountered a pointer, but expected the type usize
+   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ type validation failed: encountered a pointer, but expected initialized plain bits
    |
    = note: The rules on what exactly is undefined behavior aren't clear, so this check might be overzealous. Please open an issue on the rust compiler repository if you believe it should not be considered undefined behavior
 
@@ -36,7 +36,7 @@ error[E0080]: this constant likely exhibits undefined behavior
   --> $DIR/const-pointer-values-in-various-types.rs:36:5
    |
 LL |     const I32_REF_U64_UNION: u64 = unsafe { Nonsense { int_32_ref: &3 }.uint_64 };
-   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ type validation failed: encountered a pointer, but expected the type u64
+   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ type validation failed: encountered a pointer, but expected initialized plain bits
    |
    = note: The rules on what exactly is undefined behavior aren't clear, so this check might be overzealous. Please open an issue on the rust compiler repository if you believe it should not be considered undefined behavior
 
@@ -74,7 +74,7 @@ error[E0080]: this constant likely exhibits undefined behavior
   --> $DIR/const-pointer-values-in-various-types.rs:51:5
    |
 LL |     const I32_REF_I64_UNION: i64 = unsafe { Nonsense { int_32_ref: &3 }.int_64 };
-   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ type validation failed: encountered a pointer, but expected the type i64
+   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ type validation failed: encountered a pointer, but expected initialized plain bits
    |
    = note: The rules on what exactly is undefined behavior aren't clear, so this check might be overzealous. Please open an issue on the rust compiler repository if you believe it should not be considered undefined behavior
 
@@ -96,7 +96,7 @@ error[E0080]: this constant likely exhibits undefined behavior
   --> $DIR/const-pointer-values-in-various-types.rs:60:5
    |
 LL |     const I32_REF_F64_UNION: f64 = unsafe { Nonsense { int_32_ref: &3 }.float_64 };
-   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ type validation failed: encountered a pointer, but expected the type f64
+   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ type validation failed: encountered a pointer, but expected initialized plain bits
    |
    = note: The rules on what exactly is undefined behavior aren't clear, so this check might be overzealous. Please open an issue on the rust compiler repository if you believe it should not be considered undefined behavior
 
@@ -144,7 +144,7 @@ error[E0080]: this constant likely exhibits undefined behavior
   --> $DIR/const-pointer-values-in-various-types.rs:78:5
    |
 LL |     const STR_U64_UNION: u64 = unsafe { Nonsense { stringy: "3" }.uint_64 };
-   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ type validation failed: encountered a pointer, but expected the type u64
+   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ type validation failed: encountered a pointer, but expected initialized plain bits
    |
    = note: The rules on what exactly is undefined behavior aren't clear, so this check might be overzealous. Please open an issue on the rust compiler repository if you believe it should not be considered undefined behavior
 
@@ -184,7 +184,7 @@ error[E0080]: this constant likely exhibits undefined behavior
   --> $DIR/const-pointer-values-in-various-types.rs:93:5
    |
 LL |     const STR_I64_UNION: i64 = unsafe { Nonsense { stringy: "3" }.int_64 };
-   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ type validation failed: encountered a pointer, but expected the type i64
+   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ type validation failed: encountered a pointer, but expected initialized plain bits
    |
    = note: The rules on what exactly is undefined behavior aren't clear, so this check might be overzealous. Please open an issue on the rust compiler repository if you believe it should not be considered undefined behavior
 
@@ -208,7 +208,7 @@ error[E0080]: this constant likely exhibits undefined behavior
   --> $DIR/const-pointer-values-in-various-types.rs:102:5
    |
 LL |     const STR_F64_UNION: f64 = unsafe { Nonsense { stringy: "3" }.float_64 };
-   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ type validation failed: encountered a pointer, but expected the type f64
+   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ type validation failed: encountered a pointer, but expected initialized plain bits
    |
    = note: The rules on what exactly is undefined behavior aren't clear, so this check might be overzealous. Please open an issue on the rust compiler repository if you believe it should not be considered undefined behavior
 

src/test/ui/consts/const-eval/transmute-const.rs

@@ -14,6 +14,5 @@ use std::mem;
 
 static FOO: bool = unsafe { mem::transmute(3u8) };
 //~^ ERROR this static likely exhibits undefined behavior
-//~^^ type validation failed: encountered 3, but expected something in the range 0..=1
 
 fn main() {}

src/test/ui/consts/const-eval/transmute-const.stderr

@@ -2,7 +2,7 @@ error[E0080]: this static likely exhibits undefined behavior
   --> $DIR/transmute-const.rs:15:1
    |
 LL | static FOO: bool = unsafe { mem::transmute(3u8) };
-   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ type validation failed: encountered 3, but expected something in the range 0..=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 rust compiler repository if you believe it should not be considered undefined behavior
 

src/test/ui/consts/const-eval/ub-enum.stderr

@@ -18,7 +18,7 @@ error[E0080]: this constant likely exhibits undefined behavior
   --> $DIR/ub-enum.rs:45:1
    |
 LL | const BAD_ENUM_CHAR : Option<(char, char)> = Some(('x', unsafe { TransmuteChar { a: !0 }.b }));
-   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ type validation failed: encountered character at .Some.0.1, but expected a valid unicode codepoint
+   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ type validation failed: encountered 4294967295 at .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 rust compiler repository if you believe it should not be considered undefined behavior
 

src/test/ui/consts/const-eval/ub-ref.rs

@@ -8,13 +8,17 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
-union Foo {
-    a: &'static u8,
-    b: usize,
-}
+#![feature(const_transmute)]
 
-const USIZE_AS_STATIC_REF: &'static u8 = unsafe { Foo { b: 1337 }.a};
+use std::mem;
+
+const UNALIGNED: &u16 = unsafe { mem::transmute(&[0u8; 4]) };
 //~^ ERROR this constant likely exhibits undefined behavior
 
-fn main() {
-}
+const REF_AS_USIZE: usize = unsafe { mem::transmute(&0) };
+//~^ ERROR this constant likely exhibits undefined behavior
+
+const USIZE_AS_REF: &'static u8 = unsafe { mem::transmute(1337usize) };
+//~^ ERROR this constant likely exhibits undefined behavior
+
+fn main() {}

src/test/ui/consts/const-eval/ub-ref.stderr

@@ -0,0 +1,27 @@
+error[E0080]: this constant likely exhibits undefined behavior
+  --> $DIR/ub-ref.rs:15:1
+   |
+LL | const UNALIGNED: &u16 = unsafe { mem::transmute(&[0u8; 4]) };
+   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ type validation failed: encountered unaligned 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 rust compiler repository if you believe it should not be considered undefined behavior
+
+error[E0080]: this constant likely exhibits undefined behavior
+  --> $DIR/ub-ref.rs:18:1
+   |
+LL | const REF_AS_USIZE: usize = unsafe { mem::transmute(&0) };
+   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ type validation failed: encountered a pointer, but expected initialized plain bits
+   |
+   = note: The rules on what exactly is undefined behavior aren't clear, so this check might be overzealous. Please open an issue on the rust compiler repository if you believe it should not be considered undefined behavior
+
+error[E0080]: this constant likely exhibits undefined behavior
+  --> $DIR/ub-ref.rs:21:1
+   |
+LL | const USIZE_AS_REF: &'static u8 = unsafe { mem::transmute(1337usize) };
+   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ type validation failed: encountered integer pointer in non-ZST 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 rust compiler repository if you believe it should not be considered undefined behavior
+
+error: aborting due to 3 previous errors
+
+For more information about this error, try `rustc --explain E0080`.

src/test/ui/consts/const-eval/ub-usize-in-ref.stderr

@@ -1,11 +0,0 @@
-error[E0080]: this constant likely exhibits undefined behavior
-  --> $DIR/ub-usize-in-ref.rs:16:1
-   |
-LL | const USIZE_AS_STATIC_REF: &'static u8 = unsafe { Foo { b: 1337 }.a};
-   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ type validation failed: encountered integer pointer in non-ZST 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 rust compiler repository if you believe it should not be considered undefined behavior
-
-error: aborting due to previous error
-
-For more information about this error, try `rustc --explain E0080`.

src/test/ui/consts/const-eval/union-ice.stderr

@@ -13,7 +13,7 @@ LL | / const FIELD_PATH: Struct = Struct { //~ ERROR this constant likely exhibi
 LL | |     a: 42,
 LL | |     b: unsafe { UNION.field3 },
 LL | | };
-   | |__^ type validation failed: encountered undefined bytes at .b
+   | |__^ type validation failed: encountered uninitialized bytes at .b, but expected initialized plain bits
    |
    = note: The rules on what exactly is undefined behavior aren't clear, so this check might be overzealous. Please open an issue on the rust compiler repository if you believe it should not be considered undefined behavior
 

src/test/ui/consts/const-eval/union-ub.rs

@@ -41,5 +41,4 @@ const BAD_BOOL: bool = unsafe { DummyUnion { u8: 42 }.bool};
 const BAD_UNION: Foo = unsafe { Bar { u8: 42 }.foo };
 
 
-fn main() {
-}
+fn main() {}

src/test/ui/consts/const-eval/union-ub.stderr

@@ -2,7 +2,7 @@ error[E0080]: this constant likely exhibits undefined behavior
   --> $DIR/union-ub.rs:36:1
    |
 LL | const BAD_BOOL: bool = unsafe { DummyUnion { u8: 42 }.bool};
-   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ type validation failed: encountered 42, but expected something in the range 0..=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 rust compiler repository if you believe it should not be considered undefined behavior
 

src/test/ui/union-ub-fat-ptr.stderr

@@ -66,7 +66,7 @@ error[E0080]: this constant likely exhibits undefined behavior
   --> $DIR/union-ub-fat-ptr.rs:116:1
    |
 LL | const G: &Trait = &unsafe { BoolTransmute { val: 3 }.bl };
-   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ type validation failed: encountered 3 at .<deref>, but expected something in the range 0..=1
+   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ type validation failed: encountered 3 at .<deref>, 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 rust compiler repository if you believe it should not be considered undefined behavior
 
@@ -74,7 +74,7 @@ error[E0080]: this constant likely exhibits undefined behavior
   --> $DIR/union-ub-fat-ptr.rs:119:1
    |
 LL | const H: &[bool] = &[unsafe { BoolTransmute { val: 3 }.bl }];
-   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ type validation failed: encountered 3 at .<deref>[0], but expected something in the range 0..=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 rust compiler repository if you believe it should not be considered undefined behavior
 
@@ -82,7 +82,7 @@ error[E0080]: this constant likely exhibits undefined behavior
   --> $DIR/union-ub-fat-ptr.rs:125:1
    |
 LL | const I2: &MySliceBool = &MySlice(unsafe { BoolTransmute { val: 3 }.bl }, [false]);
-   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ type validation failed: encountered 3 at .<deref>.0, but expected something in the range 0..=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 rust compiler repository if you believe it should not be considered undefined behavior
 
@@ -90,7 +90,7 @@ error[E0080]: this constant likely exhibits undefined behavior
   --> $DIR/union-ub-fat-ptr.rs:128:1
    |
 LL | const I3: &MySliceBool = &MySlice(true, [unsafe { BoolTransmute { val: 3 }.bl }]);
-   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ type validation failed: encountered 3 at .<deref>.1[0], but expected something in the range 0..=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 rust compiler repository if you believe it should not be considered undefined behavior