[clang] [C++20][Modules][NFC] Some minor comment fixes (PR #172524)

[Hubert Tong via cfe-commits]

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@@ -4441,9 +4441,9 @@ class ASTDeclContextNameLookupTrait
 
       DeclIDs.push_back(ID);
     };
+    ASTReader *Chain = Writer.getChain();
     for (NamedDecl *D : Decls) {
-      if (ASTReader *Chain = Writer.getChain();
-          Chain && isa<NamespaceDecl>(D) && D->isFromASTFile() &&
+      if (Chain && isa<NamespaceDecl>(D) && D->isFromASTFile() &&
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hubert-reinterpretcast wrote:

This part is NFC, but not a "minor comment fix".

https://github.com/llvm/llvm-project/pull/172524