[CSApply] Support dynamic member lookup as component of key path dynamic member lookup

Previously solution application only supported references to
key path dynamic member lookup as components but it should support both kinds.

Resolves: rdar://problem/60225883
Resolves: [SR-12313](https://bugs.swift.org/browse/SR-12313)

Author: xedin

lib/Sema/CSApply.cpp

@@ -1966,8 +1966,9 @@ namespace {
 
       // Looks like there is a chain of implicit `subscript(dynamicMember:)`
       // calls necessary to resolve a member reference.
-      if (overload.choice.getKind() ==
-          OverloadChoiceKind::KeyPathDynamicMemberLookup) {
+      switch (overload.choice.getKind()) {
+      case OverloadChoiceKind::DynamicMemberLookup:
+      case OverloadChoiceKind::KeyPathDynamicMemberLookup: {
         buildKeyPathSubscriptComponent(overload, dotLoc, /*indexExpr=*/nullptr,
                                        ctx.Id_dynamicMember, componentLoc,
                                        components);
@@ -1976,6 +1977,10 @@ namespace {
         return keyPath;
       }
 
+      default:
+        break;
+      }
+
       // We can't reuse existing expression because type-check
       // based diagnostics could hold the reference to original AST.
       Expr *componentExpr = nullptr;

test/attr/attr_dynamic_member_lookup.swift

@@ -764,3 +764,28 @@ func test_infinite_self_recursion() {
   _ = Recurse<Int>().foo
   // expected-error@-1 {{value of type 'Recurse<Int>' has no dynamic member 'foo' using key path from root type 'Recurse<Int>'}}
 }
+
+// rdar://problem/60225883 - crash during solution application (ExprRewritter::buildKeyPathDynamicMemberIndexExpr)
+func test_combination_of_keypath_and_string_lookups() {
+  @dynamicMemberLookup
+  struct Outer {
+    subscript(dynamicMember member: String) -> Outer {
+      Outer()
+    }
+
+    subscript(dynamicMember member: KeyPath<Inner, Inner>) -> Outer {
+      Outer()
+    }
+  }
+
+  @dynamicMemberLookup
+  struct Inner {
+    subscript(dynamicMember member: String) -> Inner {
+      Inner()
+    }
+  }
+
+  func test(outer: Outer) {
+    _ = outer.hello.world // Ok
+  }
+}