prefer default type parameter than constraint for quick info

Author: ShuiRuTian

src/compiler/checker.ts

@@ -30243,13 +30243,12 @@ namespace ts {
         }
 
         function getTypeArgumentsFromNodes(typeArgumentNodes: readonly TypeNode[], typeParameters: readonly TypeParameter[], isJs: boolean): readonly Type[] {
-            let typeArguments = typeArgumentNodes.map(getTypeOfNode);
+            const typeArguments = typeArgumentNodes.map(getTypeOfNode);
             while (typeArguments.length > typeParameters.length) {
                 typeArguments.pop();
             }
-            typeArguments = fillMissingTypeArguments(typeArguments, typeParameters, getMinTypeArgumentCount(typeParameters), isJs);
             while (typeArguments.length < typeParameters.length) {
-                typeArguments.push(getConstraintOfTypeParameter(typeParameters[typeArguments.length]) || getDefaultTypeArgumentType(isJs));
+                typeArguments.push(getDefaultFromTypeParameter(typeParameters[typeArguments.length]) || getConstraintOfTypeParameter(typeParameters[typeArguments.length]) || getDefaultTypeArgumentType(isJs));
             }
             return typeArguments;
         }

tests/cases/fourslash/signatureHelpExplicitTypeArguments.ts

@@ -1,10 +1,22 @@
 /// <reference path='fourslash.ts'/>
 
-////declare function f<T = boolean, U = string>(x: T, y: U): T;
-////f<number, string>(/*1*/);
-////f(/*2*/);
-////f<number>(/*3*/);
-////f<number, string, boolean>(/*4*/);
+//// declare function f<T = boolean, U = string>(x: T, y: U): T;
+//// f<number, string>(/*1*/);
+//// f(/*2*/);
+//// f<number>(/*3*/);
+//// f<number, string, boolean>(/*4*/);
+
+//// interface A { a: number }
+//// interface B extends A { b: string }
+//// declare function g<T, U, V extends A = B>(x: T, y: U, z: V): T;
+//// declare function h<T, U, V extends A>(x: T, y: U, z: V): T;
+//// declare function j<T, U, V = B>(x: T, y: U, z: V): T;
+//// g(/*5*/);
+//// h(/*6*/);
+//// j(/*7*/);
+//// g<number>(/*8*/);
+//// h<number>(/*9*/);
+//// j<number>(/*10*/);
 
 verify.signatureHelp(
     { marker: "1", text: "f(x: number, y: string): number" },
@@ -13,4 +25,13 @@ verify.signatureHelp(
     { marker: "3", text: "f(x: number, y: string): number" },
     // too many -- ignore extra type arguments
     { marker: "4", text: "f(x: number, y: string): number" },
+
+    // not matched signature and no type arguments
+    { marker: "5", text: "g(x: unknown, y: unknown, z: B): unknown" },
+    { marker: "6", text: "h(x: unknown, y: unknown, z: A): unknown" },
+    { marker: "7", text: "j(x: unknown, y: unknown, z: B): unknown" },
+    // not matched signature and too few type arguments
+    { marker: "8", text: "g(x: number, y: unknown, z: B): number" },
+    { marker: "9", text: "h(x: number, y: unknown, z: A): number" },
+    { marker: "10", text: "j(x: number, y: unknown, z: B): number" },
 );