[clang] [-Wunsafe-buffer-usage] Introduce std::array fixits (PR #80084)

[Ziqing Luo via cfe-commits]

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@@ -2495,10 +2471,100 @@ static FixItList fixVariableWithSpan(const VarDecl *VD,
   return fixLocalVarDeclWithSpan(VD, Ctx, getUserFillPlaceHolder(), Handler);
 }
 
+static FixItList fixVarDeclWithArray(const VarDecl *D, const ASTContext &Ctx,
+                                     UnsafeBufferUsageHandler &Handler) {
+  FixItList FixIts{};
+
+  if (auto CAT = dyn_cast<clang::ConstantArrayType>(D->getType())) {
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ziqingluo-90 wrote:

nitpick:  can we replace this check with an assertion?   Because it is already checked at the caller:
```
 case FixitStrategy::Kind::Array: {
    if (VD->isLocalVarDecl() && isa<clang::ConstantArrayType>(VD->getType()))
      return fixVariableWithArray(VD, Tracker, Ctx, Handler);
```

https://github.com/llvm/llvm-project/pull/80084