[clang] [Clang][Sema] Refactor collection of multi-level template argument lists (PR #106585)

[Younan Zhang via cfe-commits]

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@@ -1669,25 +1640,43 @@ namespace {
 
     ExprResult RebuildLambdaExpr(SourceLocation StartLoc, SourceLocation EndLoc,
                                  LambdaScopeInfo *LSI) {
+#if 1
       CXXMethodDecl *MD = LSI->CallOperator;
-      for (ParmVarDecl *PVD : MD->parameters()) {
-        assert(PVD && "null in a parameter list");
-        if (!PVD->hasDefaultArg())
-          continue;
-        Expr *UninstExpr = PVD->getUninstantiatedDefaultArg();
-        // FIXME: Obtain the source location for the '=' token.
-        SourceLocation EqualLoc = UninstExpr->getBeginLoc();
-        if (SemaRef.SubstDefaultArgument(EqualLoc, PVD, TemplateArgs)) {
-          // If substitution fails, the default argument is set to a
-          // RecoveryExpr that wraps the uninstantiated default argument so
-          // that downstream diagnostics are omitted.
-          ExprResult ErrorResult = SemaRef.CreateRecoveryExpr(
-              UninstExpr->getBeginLoc(), UninstExpr->getEndLoc(),
-              { UninstExpr }, UninstExpr->getType());
-          if (ErrorResult.isUsable())
-            PVD->setDefaultArg(ErrorResult.get());
+      // if (MD->getParentFunctionOrMethod()) {
+      if (true) {
+#if 0
+        NamedDecl *Pattern = MD;
+          std::optional<ArrayRef<TemplateArgument>> Innermost;
+        if (FunctionTemplateDecl *FTD = MD->getDescribedFunctionTemplate()) {
+          Pattern = FTD;
+          Innermost = FTD->getInjectedTemplateArgs();
+        }
+        MultiLevelTemplateArgumentList MLTAL =
+            SemaRef.getTemplateInstantiationArgs(Pattern, Pattern->getLexicalDeclContext(),
+                                                 /*Final=*/false, Innermost,
+                                                 /*RelativeToPrimary=*/true);
+#endif
+        ;
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zyn0217 wrote:

Does that still affect anything? Given that we have a similar pattern in `InstantiateDefaultArgument`, should we move the logic there?

https://github.com/llvm/llvm-project/pull/106585