Improved argument description for parameters originating from tuples

src/compiler/checker.ts

@@ -232,6 +232,7 @@ namespace ts {
             getResolvedSignatureForSignatureHelp: (node, candidatesOutArray, agumentCount) =>
                 getResolvedSignatureWorker(node, candidatesOutArray, agumentCount, CheckMode.IsForSignatureHelp),
             getExpandedParameters,
+            hasEffectiveRestParameter,
             getConstantValue: nodeIn => {
                 const node = getParseTreeNode(nodeIn, canHaveConstantValue);
                 return node ? getConstantValue(node) : undefined;

src/compiler/types.ts

@@ -3171,6 +3171,7 @@ namespace ts {
         getResolvedSignature(node: CallLikeExpression, candidatesOutArray?: Signature[], argumentCount?: number): Signature | undefined;
         /* @internal */ getResolvedSignatureForSignatureHelp(node: CallLikeExpression, candidatesOutArray?: Signature[], argumentCount?: number): Signature | undefined;
         /* @internal */ getExpandedParameters(sig: Signature): ReadonlyArray<Symbol>;
+        /* @internal */ hasEffectiveRestParameter(sig: Signature): boolean;
         getSignatureFromDeclaration(declaration: SignatureDeclaration): Signature | undefined;
         isImplementationOfOverload(node: SignatureDeclaration): boolean | undefined;
         isUndefinedSymbol(symbol: Symbol): boolean;

src/services/signatureHelp.ts

@@ -566,7 +566,7 @@ namespace ts.SignatureHelp {
     }
 
     function itemInfoForParameters(candidateSignature: Signature, checker: TypeChecker, enclosingDeclaration: Node, sourceFile: SourceFile): SignatureHelpItemInfo {
-        const isVariadic = candidateSignature.hasRestParameter;
+        const isVariadic = checker.hasEffectiveRestParameter(candidateSignature);
         const printer = createPrinter({ removeComments: true });
         const typeParameterParts = mapToDisplayParts(writer => {
             if (candidateSignature.typeParameters && candidateSignature.typeParameters.length) {

tests/cases/fourslash/signatureHelpCallExpressionTuples.ts

@@ -0,0 +1,56 @@
+/// <reference path='fourslash.ts'/>
+
+
+//// function fnTest(str: string, num: number) { }
+//// declare function wrap<A extends any[], R>(fn: (...a: A) => R) : (...a: A) => R;
+//// var fnWrapped = wrap(fnTest);
+//// fnWrapped/*3*/(/*1*/'', /*2*/5);
+//// function fnTestVariadic (str: string, ...num: number[]) { }
+//// var fnVariadicWrapped = wrap(fnTestVariadic);
+//// fnVariadicWrapped/*4*/(/*5*/'', /*6*/5);
+//// function fnNoParams () { }
+//// var fnNoParamsWrapped = wrap(fnNoParams);
+//// fnNoParamsWrapped/*7*/(/*8*/);
+
+verify.quickInfoAt("3", "var fnWrapped: (str: string, num: number) => void");
+verify.signatureHelp(
+    {
+        marker: "1",
+        text: "fnWrapped(str: string, num: number): void",
+        parameterCount: 2,
+        parameterName: "str",
+        parameterSpan: "str: string",
+    },
+    {
+        marker: "2",
+        parameterName: "num",
+        parameterSpan: "num: number",
+    },
+);
+
+verify.quickInfoAt("4", "var fnVariadicWrapped: (str: string, ...num: number[]) => void");
+verify.signatureHelp(
+    {
+        marker: "5",
+        text: "fnVariadicWrapped(str: string, ...num: number[]): void",
+        parameterCount: 2,
+        parameterName: "str",
+        parameterSpan: "str: string",
+        isVariadic: true,
+    },
+    {
+        marker: "6",
+        parameterName: "num",
+        parameterSpan: "...num: number[]",
+        isVariadic: true,
+    },
+);
+
+verify.quickInfoAt("7", "var fnNoParamsWrapped: () => void");
+verify.signatureHelp(
+    {
+        marker: "8",
+        text: "fnNoParamsWrapped(): void",
+        parameterCount: 0,
+    }
+);