[clang] [clang-tools-extra] [CLANGD] Do not crash on designator initialization of union (PR #83369)

[Nathan Ridge via cfe-commits]

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@@ -4601,8 +4601,15 @@ SourceRange DesignatedInitExpr::getDesignatorsSourceRange() const {
 SourceLocation DesignatedInitExpr::getBeginLoc() const {
   auto *DIE = const_cast<DesignatedInitExpr *>(this);
   Designator &First = *DIE->getDesignator(0);
-  if (First.isFieldDesignator())
-    return GNUSyntax ? First.getFieldLoc() : First.getDotLoc();
+  if (First.isFieldDesignator()) {
+    for (unsigned int i = 0; i < DIE->size(); i++) {
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HighCommander4 wrote:

Please add a comment explaining what this code is doing. Something like:

```c++
// Skip past implicit designators for anonymous structs/unions, since
// these do not have valid source locations.
```

https://github.com/llvm/llvm-project/pull/83369