treat TS only keywords as identifiers in jsdoc comments

src/compiler/parser.ts

@@ -6160,7 +6160,7 @@ namespace ts {
 
                         parseExpected(SyntaxKind.CloseBracketToken);
                     }
-                    else if (token === SyntaxKind.Identifier) {
+                    else if (token === SyntaxKind.Identifier || isTSOnlyKeyword(token)) {
                         name = parseJSDocIdentifier();
                     }
 
@@ -6259,7 +6259,7 @@ namespace ts {
                 }
 
                 function parseJSDocIdentifier(): Identifier {
-                    if (token !== SyntaxKind.Identifier) {
+                    if (token !== SyntaxKind.Identifier && !isTSOnlyKeyword(token)) {
                         parseErrorAtCurrentToken(Diagnostics.Identifier_expected);
                         return undefined;
                     }

src/compiler/utilities.ts

@@ -435,7 +435,7 @@ namespace ts {
             const { line: startLine } = getLineAndCharacterOfPosition(sourceFile, node.body.pos);
             const { line: endLine } = getLineAndCharacterOfPosition(sourceFile, node.body.end);
             if (startLine < endLine) {
-                // The arrow function spans multiple lines, 
+                // The arrow function spans multiple lines,
                 // make the error span be the first line, inclusive.
                 return createTextSpan(pos, getEndLinePosition(startLine, sourceFile) - pos + 1);
             }
@@ -1301,10 +1301,10 @@ namespace ts {
         if (node.jsDocComment) {
             return node.jsDocComment;
         }
-        // Try to recognize this pattern when node is initializer of variable declaration and JSDoc comments are on containing variable statement. 
-        // /** 
+        // Try to recognize this pattern when node is initializer of variable declaration and JSDoc comments are on containing variable statement.
+        // /**
         //   * @param {number} name
-        //   * @returns {number} 
+        //   * @returns {number}
         //   */
         // var x = function(name) { return name.length; }
         if (checkParentVariableStatement) {
@@ -1667,6 +1667,27 @@ namespace ts {
         return SyntaxKind.FirstKeyword <= token && token <= SyntaxKind.LastKeyword;
     }
 
+    // Some keywords are TypeScript only, so they should not be parsed as considered as
+    // keywords in JavaScript
+    export function isJSKeyword(token: SyntaxKind): boolean {
+        switch (token) {
+            case SyntaxKind.TypeKeyword:
+            case SyntaxKind.AsKeyword:
+            case SyntaxKind.AnyKeyword:
+            case SyntaxKind.DeclareKeyword:
+            case SyntaxKind.IsKeyword:
+            case SyntaxKind.ReadonlyKeyword:
+            case SyntaxKind.FromKeyword:
+                return false;
+            default:
+                return isKeyword(token);
+        }
+    }
+
+    export function isTSOnlyKeyword(token: SyntaxKind): boolean {
+        return isKeyword(token) && !isJSKeyword(token);
+    }
+
     export function isTrivia(token: SyntaxKind) {
         return SyntaxKind.FirstTriviaToken <= token && token <= SyntaxKind.LastTriviaToken;
     }

tests/cases/fourslash/server/jsdocParamTagSpecialKeywords.ts

@@ -0,0 +1,14 @@
+/// <reference path="../fourslash.ts"/>
+
+// @allowNonTsExtensions: true
+// @Filename: test.js
+//// /**
+////  * @param {string} type
+////  */
+//// function test(type) {
+////     type./**/
+//// }
+
+
+goTo.marker();
+verify.completionListContains("charAt");