Avoid computing the linkage too early. Don't invalidate it.

Before this patch we would compute the linkage lazily and cache it. When the
AST was modified in ways that could change the value, we would invalidate the
cache.

That was fairly brittle, since any code could ask for the a linkage before
the correct value was available.

We should change the API to one where the linkage is computed explicitly and
trying to get it when it is not available asserts.

This patch is a first step in that direction. We still compute the linkage
lazily, but instead of invalidating a cache, we assert that the AST
modifications didn't change the result.

llvm-svn: 176999

1 files changed, 23 insertions, 15 deletions

diff --git a/clang/lib/Sema/SemaOverload.cpp b/clang/lib/Sema/SemaOverload.cpp
index 16fd28e4615..3ed04657941 100644
--- a/clang/lib/Sema/SemaOverload.cpp
+++ b/clang/lib/Sema/SemaOverload.cpp
@@ -977,13 +977,8 @@ static bool canBeOverloaded(const FunctionDecl &D) {
   return true;
 }
 
-bool Sema::IsOverload(FunctionDecl *New, FunctionDecl *Old,
-                      bool UseUsingDeclRules) {
-  // If both of the functions are extern "C", then they are not
-  // overloads.
-  if (!canBeOverloaded(*Old) && !canBeOverloaded(*New))
-    return false;
-
+static bool shouldTryToOverload(Sema &S, FunctionDecl *New, FunctionDecl *Old,
+                                bool UseUsingDeclRules) {
   FunctionTemplateDecl *OldTemplate = Old->getDescribedFunctionTemplate();
   FunctionTemplateDecl *NewTemplate = New->getDescribedFunctionTemplate();
 
@@ -994,8 +989,8 @@ bool Sema::IsOverload(FunctionDecl *New, FunctionDecl *Old,
     return true;
 
   // Is the function New an overload of the function Old?
-  QualType OldQType = Context.getCanonicalType(Old->getType());
-  QualType NewQType = Context.getCanonicalType(New->getType());
+  QualType OldQType = S.Context.getCanonicalType(Old->getType());
+  QualType NewQType = S.Context.getCanonicalType(New->getType());
 
   // Compare the signatures (C++ 1.3.10) of the two functions to
   // determine whether they are overloads. If we find any mismatch
@@ -1016,7 +1011,7 @@ bool Sema::IsOverload(FunctionDecl *New, FunctionDecl *Old,
   if (OldQType != NewQType &&
       (OldType->getNumArgs() != NewType->getNumArgs() ||
        OldType->isVariadic() != NewType->isVariadic() ||
-       !FunctionArgTypesAreEqual(OldType, NewType)))
+       !S.FunctionArgTypesAreEqual(OldType, NewType)))
     return true;
 
   // C++ [temp.over.link]p4:
@@ -1032,9 +1027,9 @@ bool Sema::IsOverload(FunctionDecl *New, FunctionDecl *Old,
   // However, we don't consider either of these when deciding whether
   // a member introduced by a shadow declaration is hidden.
   if (!UseUsingDeclRules && NewTemplate &&
-      (!TemplateParameterListsAreEqual(NewTemplate->getTemplateParameters(),
-                                       OldTemplate->getTemplateParameters(),
-                                       false, TPL_TemplateMatch) ||
+      (!S.TemplateParameterListsAreEqual(NewTemplate->getTemplateParameters(),
+                                         OldTemplate->getTemplateParameters(),
+                                         false, S.TPL_TemplateMatch) ||
        OldType->getResultType() != NewType->getResultType()))
     return true;
 
@@ -1060,9 +1055,9 @@ bool Sema::IsOverload(FunctionDecl *New, FunctionDecl *Old,
         //     declarations with the same name, the same parameter-type-list, and
         //     the same template parameter lists cannot be overloaded if any of
         //     them, but not all, have a ref-qualifier (8.3.5).
-        Diag(NewMethod->getLocation(), diag::err_ref_qualifier_overload)
+        S.Diag(NewMethod->getLocation(), diag::err_ref_qualifier_overload)
           << NewMethod->getRefQualifier() << OldMethod->getRefQualifier();
-        Diag(OldMethod->getLocation(), diag::note_previous_declaration);
+        S.Diag(OldMethod->getLocation(), diag::note_previous_declaration);
       }
       return true;
     }
@@ -1082,6 +1077,19 @@ bool Sema::IsOverload(FunctionDecl *New, FunctionDecl *Old,
   return false;
 }
 
+bool Sema::IsOverload(FunctionDecl *New, FunctionDecl *Old,
+                      bool UseUsingDeclRules) {
+  if (!shouldTryToOverload(*this, New, Old, UseUsingDeclRules))
+    return false;
+
+  // If both of the functions are extern "C", then they are not
+  // overloads.
+  if (!canBeOverloaded(*Old) && !canBeOverloaded(*New))
+    return false;
+
+  return true;
+}
+
 /// \brief Checks availability of the function depending on the current
 /// function context. Inside an unavailable function, unavailability is ignored.
 ///