Fix ICE in try_to_raw_bytes when array elements have mismatched scalar

sizes

Author: reddevilmidzy

compiler/rustc_middle/src/ty/consts/valtree.rs

@@ -1,7 +1,7 @@
 use std::fmt;
 use std::ops::Deref;
 
-use rustc_abi::{FIRST_VARIANT, VariantIdx};
+use rustc_abi::{FIRST_VARIANT, Size, VariantIdx};
 use rustc_data_structures::intern::Interned;
 use rustc_hir::def::Namespace;
 use rustc_macros::{
@@ -148,7 +148,10 @@ impl<'tcx> Value<'tcx> {
         }
 
         // We create an iterator that yields `Option<u8>`
-        let iterator = self.to_branch().into_iter().map(|ct| Some(ct.try_to_leaf()?.to_u8()));
+        let iterator = self
+            .to_branch()
+            .into_iter()
+            .map(|ct| ct.try_to_leaf()?.try_to_bits(Size::from_bytes(1)).ok().map(|b| b as u8));
         // If there is `None` in the iterator, then the array is not a valid array of u8s and we return `None`
         let bytes: Vec<u8> = iterator.collect::<Option<Vec<u8>>>()?;
 

tests/ui/const-generics/mgca/array_elem_type_mismatch.rs

@@ -0,0 +1,10 @@
+//! Regression test for <https://github.com/rust-lang/rust/issues/152683>
+#![expect(incomplete_features)]
+#![feature(adt_const_params, generic_const_parameter_types, min_generic_const_args)]
+fn foo<const N: usize, const A: [u8; N]>() {}
+
+fn main() {
+    foo::<_, { [0, 1u8, 2u32, 8u64] }>();
+    //~^ ERROR the constant `2` is not of type `u8`
+    //~| ERROR the constant `8` is not of type `u8`
+}

tests/ui/const-generics/mgca/array_elem_type_mismatch.stderr

@@ -0,0 +1,14 @@
+error: the constant `2` is not of type `u8`
+  --> $DIR/array_elem_type_mismatch.rs:7:16
+   |
+LL |     foo::<_, { [0, 1u8, 2u32, 8u64] }>();
+   |                ^^^^^^^^^^^^^^^^^^^^ expected `u8`, found `u32`
+
+error: the constant `8` is not of type `u8`
+  --> $DIR/array_elem_type_mismatch.rs:7:16
+   |
+LL |     foo::<_, { [0, 1u8, 2u32, 8u64] }>();
+   |                ^^^^^^^^^^^^^^^^^^^^ expected `u8`, found `u64`
+
+error: aborting due to 2 previous errors
+

tests/ui/const-generics/mgca/wrapped_array_elem_type_mismatch.rs

@@ -0,0 +1,10 @@
+#![expect(incomplete_features)]
+#![feature(adt_const_params, min_generic_const_args)]
+
+struct ArrWrap<const N: [u8; 1]>;
+
+fn main() {
+    let _: ArrWrap<{ [1_u8] }> = ArrWrap::<{ [1_u16] }>;
+    //~^ ERROR: mismatched types
+    //~| ERROR the constant `1` is not of type `u8`
+}

tests/ui/const-generics/mgca/wrapped_array_elem_type_mismatch.stderr

@@ -0,0 +1,20 @@
+error[E0308]: mismatched types
+  --> $DIR/wrapped_array_elem_type_mismatch.rs:7:34
+   |
+LL |     let _: ArrWrap<{ [1_u8] }> = ArrWrap::<{ [1_u16] }>;
+   |            -------------------   ^^^^^^^^^^^^^^^^^^^^^^ expected `*b"\x01"`, found `[1]`
+   |            |
+   |            expected due to this
+   |
+   = note: expected struct `ArrWrap<*b"\x01">`
+              found struct `ArrWrap<[1]>`
+
+error: the constant `1` is not of type `u8`
+  --> $DIR/wrapped_array_elem_type_mismatch.rs:7:46
+   |
+LL |     let _: ArrWrap<{ [1_u8] }> = ArrWrap::<{ [1_u16] }>;
+   |                                              ^^^^^^^ expected `u8`, found `u16`
+
+error: aborting due to 2 previous errors
+
+For more information about this error, try `rustc --explain E0308`.