[clang] [Clang][AST][NFC] Store template parameter position for TemplateTypeParmType in TypeBit (PR #102481)

[Krystian Stasiowski via cfe-commits]

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@@ -6131,52 +6149,30 @@ class BTFTagAttributedType : public Type, public llvm::FoldingSetNode {
 class TemplateTypeParmType : public Type, public llvm::FoldingSetNode {
   friend class ASTContext; // ASTContext creates these
 
-  // Helper data collector for canonical types.
-  struct CanonicalTTPTInfo {
-    unsigned Depth : 15;
-    unsigned ParameterPack : 1;
-    unsigned Index : 16;
-  };
-
-  union {
-    // Info for the canonical type.
-    CanonicalTTPTInfo CanTTPTInfo;
-
-    // Info for the non-canonical type.
-    TemplateTypeParmDecl *TTPDecl;
-  };
+  // The associated TemplateTypeParmDecl for the non-canonical type.
+  TemplateTypeParmDecl *TTPDecl;
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sdkrystian wrote:

There are a few other cases where we can tail allocate data for types... I think I'll submit a patch that tail allocates members for a few other `Type` derived classes.

https://github.com/llvm/llvm-project/pull/102481