Create utility function for Associativity spelling

Author: AnthonyLatsis

include/swift/AST/AttrKind.h

@@ -40,6 +40,9 @@ enum class Associativity : uint8_t {
   Right
 };
 
+/// Returns the in-source spelling of the given associativity.
+StringRef getAssociativitySpelling(Associativity value);
+
 /// The kind of unary operator, if any.
 enum class UnaryOperatorKind : uint8_t {
   None,

lib/AST/Decl.cpp

@@ -6002,6 +6002,15 @@ SourceRange DestructorDecl::getSourceRange() const {
   return { getDestructorLoc(), getBody()->getEndLoc() };
 }
 
+StringRef swift::getAssociativitySpelling(Associativity value) {
+  switch (value) {
+  case Associativity::None: return "none";
+  case Associativity::Left: return "left";
+  case Associativity::Right: return "right";
+  }
+  llvm_unreachable("Unhandled Associativity in switch.");
+}
+
 PrecedenceGroupDecl *
 PrecedenceGroupDecl::create(DeclContext *dc,
                             SourceLoc precedenceGroupLoc,

lib/IDE/CodeCompletion.cpp

@@ -4072,9 +4072,9 @@ class CompletionLookup final : public swift::VisibleDeclConsumer {
   void getPrecedenceGroupCompletions(SyntaxKind SK) {
     switch (SK) {
     case SyntaxKind::PrecedenceGroupAssociativity:
-      addKeyword("none");
-      addKeyword("left");
-      addKeyword("right");
+      addKeyword(getAssociativitySpelling(Associativity::None));
+      addKeyword(getAssociativitySpelling(Associativity::Left));
+      addKeyword(getAssociativitySpelling(Associativity::Right));
       break;
     case SyntaxKind::PrecedenceGroupAssignment:
       addKeyword(getTokenText(tok::kw_false), Type(), SemanticContextKind::None,