Always build a new TypeSourceInfo for function templates with parameters

RecursiveASTVisitor::TraverseFunctionHelper() traverses a function's
ParmVarDecls by going to the function's getTypeSourceInfo if it exists, and
`DEF_TRAVERSE_TYPELOC(FunctionProtoType` then goes to the function's
ParmVarDecls.

For a function template that doesn't have parameters that explicitly depend on
the template parameter, we used to be clever and not build a new
TypeSourceInfo. That meant that when an instantiation of such a template is
visited, its TypeSourceInfo would point to the ParmVarDecls of the template,
not of the instantiation, which then confused clients of RecursiveASTVisitor.

So don't be clever for function templates that have parameters, even if none of
the parameters depend on the type.

Fixes PR26257.
http://reviews.llvm.org/D16478


git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@259428 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 6 insertions, 16 deletions

diff --git a/lib/Sema/SemaTemplateInstantiate.cpp b/lib/Sema/SemaTemplateInstantiate.cpp
index fb7fc109d2..56858bcc7e 100644
--- a/lib/Sema/SemaTemplateInstantiate.cpp
+++ b/lib/Sema/SemaTemplateInstantiate.cpp
@@ -1512,7 +1512,7 @@ QualType Sema::SubstType(QualType T,
 }
 
 static bool NeedsInstantiationAsFunctionType(TypeSourceInfo *T) {
-  if (T->getType()->isInstantiationDependentType() || 
+  if (T->getType()->isInstantiationDependentType() ||
       T->getType()->isVariablyModifiedType())
     return true;
 
@@ -1521,23 +1521,13 @@ static bool NeedsInstantiationAsFunctionType(TypeSourceInfo *T) {
     return false;
 
   FunctionProtoTypeLoc FP = TL.castAs<FunctionProtoTypeLoc>();
-  for (unsigned I = 0, E = FP.getNumParams(); I != E; ++I) {
-    ParmVarDecl *P = FP.getParam(I);
-
+  for (ParmVarDecl *P : FP.getParams()) {
     // This must be synthesized from a typedef.
     if (!P) continue;
 
-    // The parameter's type as written might be dependent even if the
-    // decayed type was not dependent.
-    if (TypeSourceInfo *TSInfo = P->getTypeSourceInfo())
-      if (TSInfo->getType()->isInstantiationDependentType())
-        return true;
-
-    // TODO: currently we always rebuild expressions.  When we
-    // properly get lazier about this, we should use the same
-    // logic to avoid rebuilding prototypes here.
-    if (P->hasDefaultArg())
-      return true;
+    // If there are any parameters, a new TypeSourceInfo that refers to the
+    // instantiated parameters must be built.
+    return true;
   }
 
   return false;
@@ -1556,7 +1546,7 @@ TypeSourceInfo *Sema::SubstFunctionDeclType(TypeSourceInfo *T,
   assert(!ActiveTemplateInstantiations.empty() &&
          "Cannot perform an instantiation without some context on the "
          "instantiation stack");
-  
+
   if (!NeedsInstantiationAsFunctionType(T))
     return T;