Added new keword compeltion filter for assertions

src/services/completions.ts

@@ -38,6 +38,7 @@ namespace ts.Completions {
         InterfaceElementKeywords,       // Keywords inside interface body
         ConstructorParameterKeywords,   // Keywords at constructor parameter
         FunctionLikeBodyKeywords,       // Keywords at function like body
+        TypeAssertionKeywords,
         TypeKeywords,
         Last = TypeKeywords
     }
@@ -1181,7 +1182,11 @@ namespace ts.Completions {
         function filterGlobalCompletion(symbols: Symbol[]): void {
             const isTypeOnly = isTypeOnlyCompletion();
             const allowTypes = isTypeOnly || !isContextTokenValueLocation(contextToken) && isPossiblyTypeArgumentPosition(contextToken, sourceFile, typeChecker);
-            if (isTypeOnly) keywordFilters = KeywordCompletionFilters.TypeKeywords;
+            if (isTypeOnly) {
+                keywordFilters = isInsideTypeAssertion()
+                    ? KeywordCompletionFilters.TypeAssertionKeywords
+                    : KeywordCompletionFilters.TypeKeywords;
+            }
 
             filterMutate(symbols, symbol => {
                 if (!isSourceFile(location)) {
@@ -1211,6 +1216,10 @@ namespace ts.Completions {
             });
         }
 
+        function isInsideTypeAssertion(): boolean {
+            return isAsExpression(contextToken.parent);
+        }
+
         function isTypeOnlyCompletion(): boolean {
             return insideJsDocTagTypeExpression || !isContextTokenValueLocation(contextToken) && (isPartOfTypeNode(location) || isContextTokenTypeLocation(contextToken));
         }
@@ -2057,6 +2066,8 @@ namespace ts.Completions {
                     return isParameterPropertyModifier(kind);
                 case KeywordCompletionFilters.FunctionLikeBodyKeywords:
                     return isFunctionLikeBodyKeyword(kind);
+                case KeywordCompletionFilters.TypeAssertionKeywords:
+                    return isTypeKeyword(kind) || kind === SyntaxKind.ConstKeyword;
                 case KeywordCompletionFilters.TypeKeywords:
                     return isTypeKeyword(kind);
                 default:

tests/cases/fourslash/completionListAsConst.ts

@@ -0,0 +1,11 @@
+/// <reference path='fourslash.ts'/>
+
+////const a = {
+////  b: 42 as con/*0*/
+////};
+////
+////1 as con/*1*/
+////
+////const b = 42 as /*2*/
+
+verify.completions({ marker: test.markers(), includes: [{ name: "const", sortText: completion.SortText.GlobalsOrKeywords }] });