[clang] [clang] Track function template instantiation from definition (PR #110387)

[Younan Zhang via cfe-commits]

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@@ -492,8 +489,10 @@ MultiLevelTemplateArgumentList Sema::getTemplateInstantiationArgs(
     // has a depth of 0.
     if (const auto *TTP = dyn_cast<TemplateTemplateParmDecl>(CurDecl))
       HandleDefaultTempArgIntoTempTempParam(TTP, Result);
-    CurDecl = Response::UseNextDecl(CurDecl).NextDecl;
-  }
+    CurDecl = DC ? Decl::castFromDeclContext(DC)
+                 : Response::UseNextDecl(CurDecl).NextDecl;
+  } else if (!CurDecl)
+    CurDecl = Decl::castFromDeclContext(DC);
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zyn0217 wrote:

nit: We might want to keep this branch where it was. (i.e. to still put it on line 479 - 481)

(I remembered I was told handling it earlier makes things clearer, so...)

https://github.com/llvm/llvm-project/pull/110387