A parameter not declared as a rest parameter is not one (microsoft#18825)

Author: Andy

src/compiler/checker.ts

@@ -20298,7 +20298,7 @@ namespace ts {
 
         function checkCollisionWithArgumentsInGeneratedCode(node: SignatureDeclaration) {
             // no rest parameters \ declaration context \ overload - no codegen impact
-            if (!hasDeclaredRestParameter(node) || isInAmbientContext(node) || nodeIsMissing((<FunctionLikeDeclaration>node).body)) {
+            if (!hasRestParameter(node) || isInAmbientContext(node) || nodeIsMissing((<FunctionLikeDeclaration>node).body)) {
                 return;
             }
 

src/compiler/utilities.ts

@@ -1604,26 +1604,12 @@ namespace ts {
     }
 
     export function hasRestParameter(s: SignatureDeclaration): boolean {
-        return isRestParameter(lastOrUndefined(s.parameters));
+        const last = lastOrUndefined(s.parameters);
+        return last && isRestParameter(last);
     }
 
-    export function hasDeclaredRestParameter(s: SignatureDeclaration): boolean {
-        return isDeclaredRestParam(lastOrUndefined(s.parameters));
-    }
-
-    export function isRestParameter(node: ParameterDeclaration) {
-        if (isInJavaScriptFile(node)) {
-            if (node.type && node.type.kind === SyntaxKind.JSDocVariadicType ||
-                forEach(getJSDocParameterTags(node),
-                    t => t.typeExpression && t.typeExpression.type.kind === SyntaxKind.JSDocVariadicType)) {
-                return true;
-            }
-        }
-        return isDeclaredRestParam(node);
-    }
-
-    export function isDeclaredRestParam(node: ParameterDeclaration) {
-        return node && node.dotDotDotToken !== undefined;
+    export function isRestParameter(node: ParameterDeclaration): boolean {
+        return node.dotDotDotToken !== undefined;
     }
 
     export const enum AssignmentKind {

tests/baselines/reference/jsFileCompilationRestParamJsDocFunction.types

@@ -10,7 +10,7 @@
  * @returns {*} Returns the result of `func`.
  */
 function apply(func, thisArg, args) {
->apply : (func: Function, thisArg: any, ...args: any[]) => any
+>apply : (func: Function, thisArg: any, args: any[]) => any
 >func : Function
 >thisArg : any
 >args : any[]
@@ -84,5 +84,5 @@ function apply(func, thisArg, args) {
 }
 
 export default apply;
->apply : (func: Function, thisArg: any, ...args: any[]) => any
+>apply : (func: Function, thisArg: any, args: any[]) => any
 

tests/baselines/reference/jsdocPrefixPostfixParsing.types

@@ -16,7 +16,7 @@
  * @param {...number?[]!} k - (number[] | null)[]
  */
 function f(x, y, z, a, b, c, d, e, f, g, h, i, j, k) {
->f : (x: number[], y: number[], z: number[], a: (number | null)[], b: number[] | null, c: number[] | null, d: number[] | null, ...e: (number | null)[], f: number[] | null, g: number[] | null, h: number[] | null, i: number[][], j: number[][] | null, k: (number[] | null)[]) => void
+>f : (x: number[], y: number[], z: number[], a: (number | null)[], b: number[] | null, c: number[] | null, d: number[] | null, e: (number | null)[], f: number[] | null, g: number[] | null, h: number[] | null, i: number[][], j: number[][] | null, k: (number[] | null)[]) => void
 >x : number[]
 >y : number[]
 >z : number[]