[clang] [mlir] [Clang]Check for a valid Index in array before getting it (PR #172399)

[via cfe-commits]

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@@ -0,0 +1,13 @@
+// RUN: %clang_cc1  --std=c++17  -fexperimental-new-constant-interpreter -verify=experiment %s
+// RUN: %clang_cc1  --std=c++17  -triple x86_64-pc-win32 -verify=experiment %s
+// RUN: %clang_cc1  --std=c++17  -triple x86_64-pc-linux -verify=none %s
+
+#ifndef _MSC_VER
+// none-no-diagnostics
----------------
Sirraide wrote:

Yeah, the diagnostics we’re getting make sense, but I would also expect them on linux and not just windows
```
2025-12-23T01:05:27.5562875Z # | error: 'none-error' diagnostics seen but not expected: 
2025-12-23T01:05:27.5563481Z # |   File C:\_work\llvm-project\llvm-project\clang\test\AST\array-overflow-index.cpp Line 8: constexpr function never produces a constant expression
2025-12-23T01:05:27.5564065Z # | error: 'none-note' diagnostics seen but not expected: 
2025-12-23T01:05:27.5565264Z # |   File C:\_work\llvm-project\llvm-project\clang\test\AST\array-overflow-index.cpp Line 9: cannot refer to element 4294967295 of array of 1 element in a constant expression
2025-12-23T01:05:27.5566033Z # | 2 errors generated.
```

https://github.com/llvm/llvm-project/pull/172399