Update Miri tests

Author: shepmaster

compiler/base/orchestrator/src/coordinator.rs

@@ -3857,8 +3857,7 @@ mod tests {
         let req = MiriRequest {
             code: r#"
                 fn main() {
-                    let mut a: [u8; 0] = [];
-                    unsafe { *a.get_unchecked_mut(1) = 1; }
+                    unsafe { core::mem::MaybeUninit::<u8>::uninit().assume_init() };
                 }
                 "#
             .into(),
@@ -3870,10 +3869,8 @@ mod tests {
         assert!(!response.success, "stderr: {}", response.stderr);
 
         assert_contains!(response.stderr, "Undefined Behavior");
-        assert_contains!(response.stderr, "pointer to 1 byte");
-        assert_contains!(response.stderr, "starting at offset 0");
-        assert_contains!(response.stderr, "is out-of-bounds");
-        assert_contains!(response.stderr, "has size 0");
+        assert_contains!(response.stderr, "using uninitialized data");
+        assert_contains!(response.stderr, "operation requires initialized memory");
 
         coordinator.shutdown().await?;
 

tests/spec/features/tools_spec.rb

@@ -42,15 +42,14 @@ def code_with_lint_warnings
     in_tools_menu { click_on("Miri") }
 
     within(:output, :stderr) do
-      expect(page).to have_content %r{alloc\d+ has size 0, so pointer to 1 byte starting at offset 0 is out-of-bounds}, wait: 10
+      expect(page).to have_content %r{using uninitialized data, but this operation requires initialized memory}, wait: 10
     end
   end
 
   def code_with_undefined_behavior
     <<~EOF
     fn main() {
-        let mut a: [u8; 0] = [];
-        unsafe { *a.get_unchecked_mut(1) = 1; }
+        unsafe { core::mem::MaybeUninit::<u8>::uninit().assume_init() };
     }
     EOF
   end