[modules] PR28812: Modules can return duplicate field decls.

If two modules contain duplicate class definitions the lookup result can contain
more than 2 elements. Sift the lookup results until we find a field decl.

It is not necessary to do ODR checks in place as they done elsewhere.

This should fix issues when compiling with libstdc++ 5.2 and 6.2.

Patch developed in collaboration with Richard Smith!

llvm-svn: 285184

1 files changed, 9 insertions, 2 deletions

diff --git a/clang/lib/Sema/SemaDeclCXX.cpp b/clang/lib/Sema/SemaDeclCXX.cpp
index f49525c6e45..518a780a4ea 100644
--- a/clang/lib/Sema/SemaDeclCXX.cpp
+++ b/clang/lib/Sema/SemaDeclCXX.cpp
@@ -12321,13 +12321,20 @@ ExprResult Sema::BuildCXXDefaultInitExpr(SourceLocation Loc, FieldDecl *Field) {
     // Lookup can return at most two results: the pattern for the field, or the
     // injected class name of the parent record. No other member can have the
     // same name as the field.
-    assert(!Lookup.empty() && Lookup.size() <= 2 &&
+    // In modules mode, lookup can return multiple results (coming from
+    // different modules).
+    assert((getLangOpts().Modules || (!Lookup.empty() && Lookup.size() <= 2)) &&
            "more than two lookup results for field name");
     FieldDecl *Pattern = dyn_cast<FieldDecl>(Lookup[0]);
     if (!Pattern) {
       assert(isa<CXXRecordDecl>(Lookup[0]) &&
              "cannot have other non-field member with same name");
-      Pattern = cast<FieldDecl>(Lookup[1]);
+      for (auto L : Lookup)
+        if (isa<FieldDecl>(L)) {
+          Pattern = cast<FieldDecl>(L);
+          break;
+        }
+      assert(Pattern && "We must have set the Pattern!");
     }
 
     if (InstantiateInClassInitializer(Loc, Field, Pattern,