Add asserts to type only symbols meaning exclusion (#43382)

Fixes #42180

Author: saitonakamura

src/services/completions.ts

@@ -1659,8 +1659,9 @@ namespace ts.Completions {
 
         function isContextTokenValueLocation(contextToken: Node) {
             return contextToken &&
-                contextToken.kind === SyntaxKind.TypeOfKeyword &&
-                (contextToken.parent.kind === SyntaxKind.TypeQuery || isTypeOfExpression(contextToken.parent));
+                ((contextToken.kind === SyntaxKind.TypeOfKeyword &&
+                    (contextToken.parent.kind === SyntaxKind.TypeQuery || isTypeOfExpression(contextToken.parent))) ||
+                (contextToken.kind === SyntaxKind.AssertsKeyword && contextToken.parent.kind === SyntaxKind.TypePredicate));
         }
 
         function isContextTokenTypeLocation(contextToken: Node): boolean {

tests/cases/fourslash/completionsAsserts.ts

@@ -0,0 +1,8 @@
+/// <reference path="fourslash.ts" />
+
+////declare function assert(argument1: any): asserts a/**/
+
+verify.completions({
+    marker: "",
+    includes: { name: "argument1" }
+});