[CodeCompletion] Don't mark #keyPath as "expression specific" without # (#2797)

We suggest #keyPath in every String context, so having it be
expression-specific is artificially increasing its priority.

rdar://problem/26544672

Author: benlangmuir

lib/IDE/CodeCompletion.cpp

@@ -2196,11 +2196,15 @@ class CompletionLookup final : public swift::VisibleDeclConsumer {
     // #keyPath is only available when the Objective-C runtime is.
     if (!Ctx.LangOpts.EnableObjCInterop) return;
 
+    // After #, this is a very likely result. When just in a String context,
+    // it's not.
+    auto semanticContext = needPound ? SemanticContextKind::None
+                                     : SemanticContextKind::ExpressionSpecific;
+
     CodeCompletionResultBuilder Builder(
                                   Sink,
                                   CodeCompletionResult::ResultKind::Keyword,
-                                  SemanticContextKind::ExpressionSpecific,
-                                  ExpectedTypes);
+                                  semanticContext, ExpectedTypes);
     if (needPound)
       Builder.addTextChunk("#keyPath");
     else

test/IDE/complete_pound_keypath.swift

@@ -36,7 +36,7 @@ func completeInKeyPath2() {
 
 // CHECK-AFTER_POUND: Keyword/ExprSpecific:               keyPath({#@objc property sequence#}); name=keyPath(@objc property sequence)
 
-// CHECK-KEYPATH_ARG: Keyword/ExprSpecific:               #keyPath({#@objc property sequence#}); name=#keyPath(@objc property sequence)
+// CHECK-KEYPATH_ARG: Keyword/None:                       #keyPath({#@objc property sequence#}); name=#keyPath(@objc property sequence)
 
 // CHECK-IN_KEYPATH: Decl[InstanceVar]/CurrNominal:      prop1[#String#]; name=prop1
 // CHECK-IN_KEYPATH: Decl[InstanceVar]/CurrNominal:      prop2[#ObjCClass?#]; name=prop2