Fix recognition of shadowed template parameter

Crash reported in PR28023 is caused by the fact that non-type template
parameters are found by tag name lookup.  In the code provided in that PR:

template<int V> struct A {
  struct B {
    template <int> friend struct V;
  };
};

the template parameter V is found when lookup for redeclarations of 'struct V'
is made. Latter on the error about shadowing of 'V' is emitted but the semantic
context of 'struct V' is already determined wrong: 'struct A' instead of
translation unit.

The fix moves the check for shadowing toward the beginning of the method and
thus prevents from wrong context calculations.

This change fixes PR28023.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@272366 91177308-0d34-0410-b5e6-96231b3b80d8

diff --git a/lib/Sema/SemaTemplate.cpp b/lib/Sema/SemaTemplate.cpp
index 73b5c44b5998a8dbc7bbe2659ae0ef81d9c08c75..2ea242fc956b89a6592850bec5007e2597950e9d 100644 (file)
--- a/lib/Sema/SemaTemplate.cpp
+++ b/lib/Sema/SemaTemplate.cpp
@@ -929,6 +929,13 @@ Sema::CheckClassTemplate(Scope *S, unsigned TagSpec, TagUseKind TUK,
   if (Previous.begin() != Previous.end())
     PrevDecl = (*Previous.begin())->getUnderlyingDecl();
 
+  if (PrevDecl && PrevDecl->isTemplateParameter()) {
+    // Maybe we will complain about the shadowed template parameter.
+    DiagnoseTemplateParameterShadow(NameLoc, PrevDecl);
+    // Just pretend that we didn't see the previous declaration.
+    PrevDecl = nullptr;
+  }
+
   // If there is a previous declaration with the same name, check
   // whether this is a valid redeclaration.
   ClassTemplateDecl *PrevClassTemplate
@@ -1054,12 +1061,7 @@ Sema::CheckClassTemplate(Scope *S, unsigned TagSpec, TagUseKind TUK,
         // definition, as part of error recovery?
         return true;
       }
-    }    
-  } else if (PrevDecl && PrevDecl->isTemplateParameter()) {
-    // Maybe we will complain about the shadowed template parameter.
-    DiagnoseTemplateParameterShadow(NameLoc, PrevDecl);
-    // Just pretend that we didn't see the previous declaration.
-    PrevDecl = nullptr;
+    }
   } else if (PrevDecl) {
     // C++ [temp]p5:
     //   A class template shall not have the same name as any other

diff --git a/test/CXX/temp/temp.res/temp.local/p6.cpp b/test/CXX/temp/temp.res/temp.local/p6.cpp
index 843b45543fcf8158bf3ea06fa342b3f4811958ba..e2aa0ff344291d2efd55742d0d2bf36b18f9b03d 100644 (file)
--- a/test/CXX/temp/temp.res/temp.local/p6.cpp
+++ b/test/CXX/temp/temp.res/temp.local/p6.cpp
@@ -5,11 +5,11 @@ namespace N {}
 template<typename T, // expected-note {{declared here}}
          typename T> struct X {}; // expected-error {{declaration of 'T' shadows template parameter}}
 
-template<typename T> struct Y { // expected-note 17{{declared here}}
+template<typename T> struct Y { // expected-note 18{{declared here}}
   template<typename T> struct A {}; // expected-error {{declaration of 'T' shadows template parameter}}
 
   struct B {
-    template<typename> struct T {}; // FIXME: desired-error {{declaration of 'T' shadows template parameter}}
+    template<typename> struct T {}; // expected-error {{declaration of 'T' shadows template parameter}}
   };
   struct C {
     template<typename> void T(); // expected-error {{declaration of 'T' shadows template parameter}}
@@ -65,11 +65,11 @@ template<typename T> struct Y { // expected-note 17{{declared here}}
   friend struct T; // expected-error {{declaration of 'T' shadows template parameter}}
 };
 
-template<int T> struct Z { // expected-note 15{{declared here}}
+template<int T> struct Z { // expected-note 16{{declared here}}
   template<typename T> struct A {}; // expected-error {{declaration of 'T' shadows template parameter}}
 
   struct B {
-    template<typename> struct T {}; // FIXME: desired-error {{declaration of 'T' shadows template parameter}}
+    template<typename> struct T {}; // expected-error {{declaration of 'T' shadows template parameter}}
   };
   struct C {
     template<typename> void T(); // expected-error {{declaration of 'T' shadows template parameter}}
@@ -129,7 +129,8 @@ void f(int T) {} // expected-error {{declaration of 'T' shadows template paramet
 
 // FIXME: These are ill-formed: a template-parameter shall not have the same name as the template name.
 namespace A {
-  template<typename T> struct T {};
+  template<typename T> struct T {};  // expected-error{{declaration of 'T' shadows template parameter}}
+                                     // expected-note@-1{{template parameter is declared here}}
 }
 namespace B {
   template<typename T> void T() {}
@@ -137,3 +138,13 @@ namespace B {
 namespace C {
   template<typename T> int T;
 }
+
+namespace PR28023 {
+template<int V>  // expected-note{{template parameter is declared here}}
+struct A {
+  struct B {
+    template <int> friend struct V;  // expected-error{{declaration of 'V' shadows template parameter}}
+  };
+};
+A<0>::B a;
+}