Sema: Fix 'for ... in ...' over a sequence of DynamicSelfType

Author: slavapestov

lib/Sema/ConstraintSystem.cpp

@@ -2194,6 +2194,8 @@ Type simplifyTypeImpl(ConstraintSystem &cs, Type type, Fn getFixedTypeFn) {
       // FIXME: It's kind of weird in general that we have to look
       // through lvalue, inout and IUO types here
       Type lookupBaseType = newBase->getWithoutSpecifierType();
+      if (auto selfType = lookupBaseType->getAs<DynamicSelfType>())
+        lookupBaseType = selfType->getSelfType();
 
       if (lookupBaseType->mayHaveMembers() ||
           lookupBaseType->is<DynamicSelfType>()) {

lib/Sema/TypeCheckConstraints.cpp

@@ -2910,6 +2910,8 @@ bool TypeChecker::typeCheckForEachBinding(DeclContext *dc, ForEachStmt *stmt) {
         lookupOptions |= NameLookupFlags::KnownPrivate;
 
       auto sequenceType = cs.getType(expr)->getRValueType();
+      if (auto *selfType = sequenceType->getAs<DynamicSelfType>())
+        sequenceType = selfType->getSelfType();
 
       // Look through one level of optional; this improves recovery but doesn't
       // change the result.

test/decl/func/dynamic_self.swift

@@ -419,3 +419,20 @@ func useSelfOperator() {
   let s = SelfOperator()
   _ = s + s
 }
+
+// for ... in loops
+
+struct DummyIterator : IteratorProtocol {
+  func next() -> Int? { return nil }
+}
+
+class Iterable : Sequence {
+  func returnsSelf() -> Self {
+    for _ in self {}
+    return self
+  }
+
+  func makeIterator() -> DummyIterator {
+    return DummyIterator()
+  }
+}