JSDoc supports null, undefined and never types

Author: sandersn

src/compiler/checker.ts

@@ -5547,6 +5547,12 @@ namespace ts {
                     return nullType;
                 case SyntaxKind.NeverKeyword:
                     return neverType;
+                case SyntaxKind.JSDocNullKeyword:
+                    return nullType;
+                case SyntaxKind.JSDocUndefinedKeyword:
+                    return undefinedType;
+                case SyntaxKind.JSDocNeverKeyword:
+                    return neverType;
                 case SyntaxKind.ThisType:
                 case SyntaxKind.ThisKeyword:
                     return getTypeFromThisTypeNode(node);

src/compiler/parser.ts

@@ -1241,7 +1241,7 @@ namespace ts {
                     // not in error recovery.  If we're in error recovery, we don't want an errant
                     // semicolon to be treated as a class member (since they're almost always used
                     // for statements.
-                    return lookAhead(isClassMemberStart) || (token() === SyntaxKind.SemicolonToken && !inErrorRecovery);
+                    return lookAhead(isClassMemberStart) || (token() === SyntaxKind.SemicolonToken && !inErrorRecovery);
                 case ParsingContext.EnumMembers:
                     // Include open bracket computed properties. This technically also lets in indexers,
                     // which would be a candidate for improved error reporting.
@@ -5890,6 +5890,9 @@ namespace ts {
                     case SyntaxKind.BooleanKeyword:
                     case SyntaxKind.SymbolKeyword:
                     case SyntaxKind.VoidKeyword:
+                    case SyntaxKind.NullKeyword:
+                    case SyntaxKind.UndefinedKeyword:
+                    case SyntaxKind.NeverKeyword:
                         return parseTokenNode<JSDocType>();
                     case SyntaxKind.StringLiteral:
                     case SyntaxKind.NumericLiteral:

src/compiler/types.ts

@@ -351,6 +351,9 @@ namespace ts {
         JSDocPropertyTag,
         JSDocTypeLiteral,
         JSDocLiteralType,
+        JSDocNullKeyword,
+        JSDocUndefinedKeyword,
+        JSDocNeverKeyword,
 
         // Synthesized list
         SyntaxList,
@@ -383,7 +386,7 @@ namespace ts {
         FirstJSDocNode = JSDocTypeExpression,
         LastJSDocNode = JSDocLiteralType,
         FirstJSDocTagNode = JSDocComment,
-        LastJSDocTagNode = JSDocLiteralType
+        LastJSDocTagNode = JSDocNeverKeyword
     }
 
     export const enum NodeFlags {

tests/baselines/reference/jsdocNeverUndefinedNull.js

@@ -0,0 +1,20 @@
+//// [in.js]
+/**
+ * @param {never} p1
+ * @param {undefined} p2
+ * @param {null} p3
+ * @returns {void} nothing
+ */
+function f(p1, p2, p3) {
+}
+
+
+//// [out.js]
+/**
+ * @param {never} p1
+ * @param {undefined} p2
+ * @param {null} p3
+ * @returns {void} nothing
+ */
+function f(p1, p2, p3) {
+}

tests/baselines/reference/jsdocNeverUndefinedNull.symbols

@@ -0,0 +1,14 @@
+=== tests/cases/conformance/jsdoc/in.js ===
+/**
+ * @param {never} p1
+ * @param {undefined} p2
+ * @param {null} p3
+ * @returns {void} nothing
+ */
+function f(p1, p2, p3) {
+>f : Symbol(f, Decl(in.js, 0, 0))
+>p1 : Symbol(p1, Decl(in.js, 6, 11))
+>p2 : Symbol(p2, Decl(in.js, 6, 14))
+>p3 : Symbol(p3, Decl(in.js, 6, 18))
+}
+

tests/baselines/reference/jsdocNeverUndefinedNull.types

@@ -0,0 +1,14 @@
+=== tests/cases/conformance/jsdoc/in.js ===
+/**
+ * @param {never} p1
+ * @param {undefined} p2
+ * @param {null} p3
+ * @returns {void} nothing
+ */
+function f(p1, p2, p3) {
+>f : (p1: never, p2: undefined, p3: null) => void
+>p1 : never
+>p2 : undefined
+>p3 : null
+}
+

tests/cases/conformance/jsdoc/jsdocNeverUndefinedNull.ts

@@ -0,0 +1,11 @@
+// @allowJs: true
+// @filename: in.js
+// @out: out.js
+/**
+ * @param {never} p1
+ * @param {undefined} p2
+ * @param {null} p3
+ * @returns {void} nothing
+ */
+function f(p1, p2, p3) {
+}