[QoI] Don't try to lookup members on incorrect type while diagnosing keypath components

While trying to diagnose problems related to keypath components
don't assume that type of the component is always correct, check
before trying to see if it's bridged type or has members.

Resolves: rdar://problem/33135487
(cherry picked from commit c45073e)

Author: xedin

lib/Sema/CSDiag.cpp

@@ -7537,6 +7537,8 @@ static bool diagnoseKeyPathComponents(ConstraintSystem *CS, KeyPathExpr *KPE,
   auto performLookup = [&](Identifier componentName, SourceLoc componentNameLoc,
                            Type &lookupType) -> LookupResult {
     assert(currentType && "Non-beginning state must have a type");
+    if (!currentType->mayHaveMembers())
+      return LookupResult();
 
     // Determine the type in which the lookup should occur. If we have
     // a bridged value type, this will be the Objective-C class to

validation-test/compiler_crashers_2_fixed/0112-rdar33135487.swift

@@ -0,0 +1,8 @@
+// RUN: not %target-swift-frontend %s -typecheck
+
+enum State<StateType> {
+  func put<StateType>() -> StateType {}
+  func put<T>(keyPath: WritableKeyPath<StateType, T>, projection: T) {
+    put(keyPath: \.age, projection: {})
+  }
+}