[Sema] Record type of identity key paths in the constraint system

If we are completing e.g. `\.self.#^COMPLETE^#` we use the type of `self` as the base type for the completion. In order to retrieve that, we need to record the type.

Fixes rdar://80271346 [SR-14887]

Author: ahoppen

lib/Sema/CSGen.cpp

@@ -3232,7 +3232,7 @@ namespace {
           break;
         }
         case KeyPathExpr::Component::Kind::Identity:
-          continue;
+          break;
         case KeyPathExpr::Component::Kind::DictionaryKey:
           llvm_unreachable("DictionaryKey only valid in #keyPath");
           break;

test/IDE/complete_swift_key_path.swift

@@ -35,6 +35,7 @@
 // RUN: %target-swift-ide-test -code-completion -source-filename %s -code-completion-token=GENERIC_KEY_PATH_BASE | %FileCheck %s -check-prefix=PERSONTYPE-DOT
 // RUN: %target-swift-ide-test -code-completion -source-filename %s -code-completion-token=GENERIC_KEY_PATH_RESULT | %FileCheck %s -check-prefix=PERSONTYPE-DOT
 
+// RUN: %target-swift-ide-test -code-completion -source-filename %s -code-completion-token=COMPLETE_AFTER_SELF | %FileCheck %s -check-prefix=OBJ-NODOT
 class Person {
     var name: String
     var friends: [Person] = []
@@ -191,3 +192,7 @@ func genericKeyPathResult<KeyPathResult>(id: KeyPath<Person, KeyPathResult>) {
   genericKeyPathResult(\.#^GENERIC_KEY_PATH_RESULT^#)
   // Same as TYPE_DOT.
 }
+
+func completeAfterSelf(people: [Person]) {
+  people.map(\.self#^COMPLETE_AFTER_SELF^#)
+}