[PATCH] D45412: [Sema] Fix PR22637 - IndirectFieldDecl's discard qualifiers during template instantiation.

[Eric Fiselier via Phabricator via cfe-commits]

EricWF created this revision.
EricWF added reviewers: rsmith, lebedev.ri, aaron.ballman, bkramer, rjmccall.

Currently Clang fails to propagate qualifiers from the `CXXThisExpr` to the rebuilt `FieldDecl` for IndirectFieldDecls. For example:

  template <class T> struct Foo {
    struct { int x; };
    int y;
    void foo() const { 
        static_assert(__is_same(int const&, decltype((y))));
        static_assert(__is_same(int const&, decltype((x)))); // assertion fails
    }
  };
  template struct Foo<int>;

The fix is to delegate rebuilding of the MemberExpr to `BuildFieldReferenceExpr` which correctly propagates the qualifiers.


Repository:
  rC Clang

https://reviews.llvm.org/D45412

Files:
  lib/Sema/TreeTransform.h
  test/SemaCXX/PR22637.cpp
  test/SemaCXX/cxx0x-nontrivial-union.cpp


Index: test/SemaCXX/cxx0x-nontrivial-union.cpp
===================================================================
--- test/SemaCXX/cxx0x-nontrivial-union.cpp
+++ test/SemaCXX/cxx0x-nontrivial-union.cpp
@@ -110,7 +110,7 @@
     }
 
     explicit operator bool() const { return has; }
-    T &operator*() const { return value; }
+    T &operator*() { return value; }
   };
 
   optional<non_trivial> o1;
Index: test/SemaCXX/PR22637.cpp
===================================================================
--- /dev/null
+++ test/SemaCXX/PR22637.cpp
@@ -0,0 +1,40 @@
+// RUN: %clang_cc1 -fsyntax-only -verify %s
+
+// expected-no-diagnostics
+
+void check(int&) = delete;
+void check(int const&) { }
+
+template <typename>
+struct A {
+    union {
+        int b;
+    };
+    struct {
+      int c;
+    };
+    union {
+      struct {
+        union {
+          struct {
+            struct {
+              int d;
+            };
+          };
+        };
+      };
+    };
+    int e;
+    void foo() const {
+      check(b);
+      check(c);
+      check(d);
+      check(d);
+      check(e);
+    }
+};
+
+int main(){
+    A<int> a;
+    a.foo();
+}
Index: lib/Sema/TreeTransform.h
===================================================================
--- lib/Sema/TreeTransform.h
+++ lib/Sema/TreeTransform.h
@@ -2249,12 +2249,11 @@
                                                 FoundDecl, Member);
       if (BaseResult.isInvalid())
         return ExprError();
-      Base = BaseResult.get();
-      ExprValueKind VK = isArrow ? VK_LValue : Base->getValueKind();
-      MemberExpr *ME = new (getSema().Context)
-          MemberExpr(Base, isArrow, OpLoc, Member, MemberNameInfo,
-                     cast<FieldDecl>(Member)->getType(), VK, OK_Ordinary);
-      return ME;
+
+      CXXScopeSpec EmptySS;
+      return getSema().BuildFieldReferenceExpr(
+          Base, isArrow, OpLoc, EmptySS, cast<FieldDecl>(Member),
+          DeclAccessPair::make(FoundDecl, FoundDecl->getAccess()), MemberNameInfo);
     }
 
     CXXScopeSpec SS;


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