Sema: Teach the solver to find members of tuples

Author: slavapestov

lib/Sema/CSSimplify.cpp

@@ -8229,27 +8229,24 @@ performMemberLookup(ConstraintKind constraintKind, DeclNameRef memberName,
   // of the tuple.
   auto &ctx = getASTContext();
   if (auto baseTuple = baseObjTy->getAs<TupleType>()) {
-    // Tuples don't have compound-name members.
-    if (!memberName.isSimpleName() || memberName.isSpecial())
-      return result;  // No result.
-
-    StringRef nameStr = memberName.getBaseIdentifier().str();
-    int fieldIdx = -1;
-    // Resolve a number reference into the tuple type.
-    unsigned Value = 0;
-    if (!nameStr.getAsInteger(10, Value) &&
-        Value < baseTuple->getNumElements()) {
-      fieldIdx = Value;
-    } else {
-      fieldIdx = baseTuple->getNamedElementId(memberName.getBaseIdentifier());
+    if (!memberName.isSpecial()) {
+      StringRef nameStr = memberName.getBaseIdentifier().str();
+      int fieldIdx = -1;
+      // Resolve a number reference into the tuple type.
+      unsigned Value = 0;
+      if (!nameStr.getAsInteger(10, Value) &&
+          Value < baseTuple->getNumElements()) {
+        fieldIdx = Value;
+      } else {
+        fieldIdx = baseTuple->getNamedElementId(memberName.getBaseIdentifier());
+      }
+
+      if (fieldIdx != -1) {
+        // Add an overload set that selects this field.
+        result.ViableCandidates.push_back(OverloadChoice(baseTy, fieldIdx));
+        return result;
+      }
     }
-    
-    if (fieldIdx == -1)
-      return result;    // No result.
-    
-    // Add an overload set that selects this field.
-    result.ViableCandidates.push_back(OverloadChoice(baseTy, fieldIdx));
-    return result;
   }
 
   if (auto *selfTy = instanceTy->getAs<DynamicSelfType>())

lib/Sema/ConstraintSystem.cpp

@@ -3621,6 +3621,12 @@ Type ConstraintSystem::simplifyTypeImpl(Type type,
         auto conformance = DC->getParentModule()->lookupConformance(
           lookupBaseType, proto);
         if (!conformance) {
+          // FIXME: This regresses diagnostics if removed, but really the
+          // handling of a missing conformance should be the same for
+          // tuples and non-tuples.
+          if (lookupBaseType->is<TupleType>())
+            return DependentMemberType::get(lookupBaseType, assocType);
+
           // If the base type doesn't conform to the associatedtype's protocol,
           // there will be a missing conformance fix applied in diagnostic mode,
           // so the concrete dependent member type is considered a "hole" in