diff --git a/src/harness/fourslash.ts b/src/harness/fourslash.ts
index 56cc2b65508..820688c1308 100644
--- a/src/harness/fourslash.ts
+++ b/src/harness/fourslash.ts
@@ -865,7 +865,7 @@ namespace FourSlash {
             ts.zipWith(actual, expected, (completion, expectedCompletion, index) => {
                 const name = typeof expectedCompletion === "string" ? expectedCompletion : expectedCompletion.name;
                 if (completion.name !== name) {
-                    this.raiseError(`${marker ? JSON.stringify(marker) : "" } Expected completion at index ${index} to be ${name}, got ${completion.name}`);
+                    this.raiseError(`${marker ? JSON.stringify(marker) : ""} Expected completion at index ${index} to be ${name}, got ${completion.name}`);
                 }
                 this.verifyCompletionEntry(completion, expectedCompletion);
             });
@@ -3759,7 +3759,7 @@ namespace FourSlashInterface {
     }
 
     export class Plugins {
-        constructor (private state: FourSlash.TestState) {
+        constructor(private state: FourSlash.TestState) {
         }
 
         public configurePlugin(pluginName: string, configuration: any): void {
@@ -4582,7 +4582,7 @@ namespace FourSlashInterface {
         export const keywords: ReadonlyArray<ExpectedCompletionEntryObject> = keywordsWithUndefined.filter(k => k.name !== "undefined");
 
         export const typeKeywords: ReadonlyArray<ExpectedCompletionEntryObject> =
-            ["false", "null", "true", "void", "any", "boolean", "keyof", "never", "number", "object", "string", "symbol", "undefined", "unique", "unknown", "bigint"].map(keywordEntry);
+            ["false", "null", "true", "void", "any", "boolean", "keyof", "never", "readonly", "number", "object", "string", "symbol", "undefined", "unique", "unknown", "bigint"].map(keywordEntry);
 
         const globalTypeDecls: ReadonlyArray<ExpectedCompletionEntryObject> = [
             interfaceEntry("Symbol"),
@@ -4698,6 +4698,9 @@ namespace FourSlashInterface {
             ];
         }
 
+        export const typeAssertionKeywords: ReadonlyArray<ExpectedCompletionEntry> =
+            globalTypesPlus([keywordEntry("const")]);
+
         function getInJsKeywords(keywords: ReadonlyArray<ExpectedCompletionEntryObject>): ReadonlyArray<ExpectedCompletionEntryObject> {
             return keywords.filter(keyword => {
                 switch (keyword.name) {
diff --git a/src/services/completions.ts b/src/services/completions.ts
index 8e7edc0b6e5..d7b40d14587 100644
--- a/src/services/completions.ts
+++ b/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
     }
@@ -441,7 +442,7 @@ namespace ts.Completions {
             (symbol.escapedName === InternalSymbolName.ExportEquals))
             // Name of "export default foo;" is "foo". Name of "export default 0" is the filename converted to camelCase.
             ? firstDefined(symbol.declarations, d => isExportAssignment(d) && isIdentifier(d.expression) ? d.expression.text : undefined)
-                || codefix.moduleSymbolToValidIdentifier(origin.moduleSymbol, target)
+            || codefix.moduleSymbolToValidIdentifier(origin.moduleSymbol, target)
             : symbol.name;
     }
 
@@ -632,9 +633,9 @@ namespace ts.Completions {
                     // At `,`, treat this as the next argument after the comma.
                     ? checker.getContextualTypeForArgumentAtIndex(argInfo.invocation, argInfo.argumentIndex + (previousToken.kind === SyntaxKind.CommaToken ? 1 : 0))
                     : isEqualityOperatorKind(previousToken.kind) && isBinaryExpression(parent) && isEqualityOperatorKind(parent.operatorToken.kind)
-                    // completion at `x ===/**/` should be for the right side
-                    ? checker.getTypeAtLocation(parent.left)
-                    : checker.getContextualType(previousToken as Expression);
+                        // completion at `x ===/**/` should be for the right side
+                        ? checker.getTypeAtLocation(parent.left)
+                        : checker.getContextualType(previousToken as Expression);
         }
     }
 
@@ -1182,7 +1183,11 @@ 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 = isTypeAssertion()
+                    ? KeywordCompletionFilters.TypeAssertionKeywords
+                    : KeywordCompletionFilters.TypeKeywords;
+            }
 
             filterMutate(symbols, symbol => {
                 if (!isSourceFile(location)) {
@@ -1212,6 +1217,10 @@ namespace ts.Completions {
             });
         }
 
+        function isTypeAssertion(): boolean {
+            return isAssertionExpression(contextToken.parent);
+        }
+
         function isTypeOnlyCompletion(): boolean {
             return insideJsDocTagTypeExpression || !isContextTokenValueLocation(contextToken) && (isPartOfTypeNode(location) || isContextTokenTypeLocation(contextToken));
         }
@@ -1240,7 +1249,8 @@ namespace ts.Completions {
                         return parentKind === SyntaxKind.AsExpression;
 
                     case SyntaxKind.LessThanToken:
-                        return parentKind === SyntaxKind.TypeReference;
+                        return parentKind === SyntaxKind.TypeReference ||
+                            parentKind === SyntaxKind.TypeAssertionExpression;
 
                     case SyntaxKind.ExtendsKeyword:
                         return parentKind === SyntaxKind.TypeParameter;
@@ -1516,7 +1526,7 @@ namespace ts.Completions {
             //   3. at the end of a regular expression (due to trailing flags like '/foo/g').
             return (isRegularExpressionLiteral(contextToken) || isStringTextContainingNode(contextToken)) && (
                 rangeContainsPositionExclusive(createTextRangeFromSpan(createTextSpanFromNode(contextToken)), position) ||
-                    position === contextToken.end && (!!contextToken.isUnterminated || isRegularExpressionLiteral(contextToken)));
+                position === contextToken.end && (!!contextToken.isUnterminated || isRegularExpressionLiteral(contextToken)));
         }
 
         /**
@@ -2026,8 +2036,8 @@ namespace ts.Completions {
 
             return baseSymbols.filter(propertySymbol =>
                 !existingMemberNames.has(propertySymbol.escapedName) &&
-                    !!propertySymbol.declarations &&
-                    !(getDeclarationModifierFlagsFromSymbol(propertySymbol) & ModifierFlags.Private));
+                !!propertySymbol.declarations &&
+                !(getDeclarationModifierFlagsFromSymbol(propertySymbol) & ModifierFlags.Private));
         }
 
         /**
@@ -2139,6 +2149,8 @@ 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:
diff --git a/src/services/utilities.ts b/src/services/utilities.ts
index 6b224df4d4d..98406c6879c 100644
--- a/src/services/utilities.ts
+++ b/src/services/utilities.ts
@@ -1224,6 +1224,7 @@ namespace ts {
         SyntaxKind.NullKeyword,
         SyntaxKind.NumberKeyword,
         SyntaxKind.ObjectKeyword,
+        SyntaxKind.ReadonlyKeyword,
         SyntaxKind.StringKeyword,
         SyntaxKind.SymbolKeyword,
         SyntaxKind.TrueKeyword,
@@ -1734,8 +1735,8 @@ namespace ts {
 
     function getSynthesizedDeepCloneWorker<T extends Node>(node: T, renameMap?: Map<Identifier>, checker?: TypeChecker, callback?: (originalNode: Node, clone: Node) => any): T {
         const visited = (renameMap || checker || callback) ?
-        visitEachChild(node, wrapper, nullTransformationContext) :
-        visitEachChild(node, getSynthesizedDeepClone, nullTransformationContext);
+            visitEachChild(node, wrapper, nullTransformationContext) :
+            visitEachChild(node, getSynthesizedDeepClone, nullTransformationContext);
 
         if (visited === node) {
             // This only happens for leaf nodes - internal nodes always see their children change.
diff --git a/tests/cases/fourslash/completionsTypeAssertionKeywords.ts b/tests/cases/fourslash/completionsTypeAssertionKeywords.ts
new file mode 100644
index 00000000000..100ab6e51e2
--- /dev/null
+++ b/tests/cases/fourslash/completionsTypeAssertionKeywords.ts
@@ -0,0 +1,13 @@
+/// <reference path='fourslash.ts'/>
+
+////const a = {
+////  b: 42 as /*0*/
+////};
+////
+////1 as /*1*/
+////
+////const b = 42 as /*2*/
+////
+////var c = </*3*/>42
+
+verify.completions({ marker: test.markers(), exact: completion.typeAssertionKeywords });
diff --git a/tests/cases/fourslash/documentHighlightsInvalidModifierLocations.ts b/tests/cases/fourslash/documentHighlightsInvalidModifierLocations.ts
index f008e632464..baa203901fd 100644
--- a/tests/cases/fourslash/documentHighlightsInvalidModifierLocations.ts
+++ b/tests/cases/fourslash/documentHighlightsInvalidModifierLocations.ts
@@ -6,5 +6,5 @@
 ////function f([|readonly|] p) {}
 
 for (const r of test.ranges()) {
-    verify.documentHighlightsOf(r, [r]);
+    verify.documentHighlightsOf(r, test.ranges());
 }
diff --git a/tests/cases/fourslash/fourslash.ts b/tests/cases/fourslash/fourslash.ts
index d74523ea7fd..73534c6c152 100644
--- a/tests/cases/fourslash/fourslash.ts
+++ b/tests/cases/fourslash/fourslash.ts
@@ -696,6 +696,7 @@ declare namespace completion {
     export const typeKeywords: ReadonlyArray<Entry>;
     export const globalTypes: ReadonlyArray<Entry>;
     export function globalTypesPlus(plus: ReadonlyArray<FourSlashInterface.ExpectedCompletionEntry>): ReadonlyArray<Entry>;
+    export const typeAssertionKeywords: ReadonlyArray<Entry>;
     export const classElementKeywords: ReadonlyArray<Entry>;
     export const classElementInJsKeywords: ReadonlyArray<Entry>;
     export const constructorParameterKeywords: ReadonlyArray<Entry>;