Support signature help for contextual parameter type (#26022)

Author: Andy

src/compiler/checker.ts

@@ -188,6 +188,10 @@ namespace ts {
                 const node = getParseTreeNode(nodeIn, isExpression);
                 return node ? getContextualType(node) : undefined;
             },
+            getContextualTypeForObjectLiteralElement: nodeIn => {
+                const node = getParseTreeNode(nodeIn, isObjectLiteralElementLike);
+                return node ? getContextualTypeForObjectLiteralElement(node) : undefined;
+            },
             getContextualTypeForArgumentAtIndex: (nodeIn, argIndex) => {
                 const node = getParseTreeNode(nodeIn, isCallLikeExpression);
                 return node && getContextualTypeForArgumentAtIndex(node, argIndex);
@@ -16219,7 +16223,7 @@ namespace ts {
                     return getContextualTypeForBinaryOperand(node);
                 case SyntaxKind.PropertyAssignment:
                 case SyntaxKind.ShorthandPropertyAssignment:
-                    return getContextualTypeForObjectLiteralElement(<ObjectLiteralElementLike>parent);
+                    return getContextualTypeForObjectLiteralElement(<PropertyAssignment | ShorthandPropertyAssignment>parent);
                 case SyntaxKind.SpreadAssignment:
                     return getApparentTypeOfContextualType(parent.parent as ObjectLiteralExpression);
                 case SyntaxKind.ArrayLiteralExpression: {

src/compiler/types.ts

@@ -2973,6 +2973,7 @@ namespace ts {
         getAugmentedPropertiesOfType(type: Type): Symbol[];
         getRootSymbols(symbol: Symbol): Symbol[];
         getContextualType(node: Expression): Type | undefined;
+        /* @internal */ getContextualTypeForObjectLiteralElement(element: ObjectLiteralElementLike): Type | undefined;
         /* @internal */ getContextualTypeForArgumentAtIndex(call: CallLikeExpression, argIndex: number): Type | undefined;
         /* @internal */ getContextualTypeForJsxAttribute(attribute: JsxAttribute | JsxSpreadAttribute): Type | undefined;
         /* @internal */ isContextSensitive(node: Expression | MethodDeclaration | ObjectLiteralElementLike | JsxAttributeLike): boolean;

src/services/signatureHelp.ts

@@ -5,9 +5,12 @@
 // @Filename: /a.tsx
 ////enum E {}
 ////enum F {}
+////interface I { e: E }
 ////function f(e: E, f: F) {}
 ////f(/*arg0*/, /*arg1*/);
 ////
+////const i: I = { e: /*prop*/ };
+////
 ////function tag(arr: TemplateStringsArray, x: E) {}
 ////tag`${/*tag*/}`;
 ////
@@ -17,6 +20,7 @@
 
 recommended("arg0");
 recommended("arg1", { enumName: "F" });
+recommended("prop");
 recommended("tag");
 recommended("jsx");
 recommended("jsx2", { insertText: "{E}" });

tests/cases/fourslash/completionsRecommended_contextualTypes.ts

@@ -20,10 +20,10 @@ verify.signatureHelp(
     { marker: "1", text: "foo1(x: number, callback: (y1: {}) => number): void" },
     // TODO: GH#23631
     // { marker: "2", text: "foo2(x: number, callback: (y2: {}) => number): void" },
-    { marker: "3", text: "foo3(x: number, callback: (y3: {}) => number): void" },
+    { marker: "3", text: "callback(y3: {}): number" },
     // TODO: GH#23631
     // { marker: "4", text: "foo4(x: number, callback: (y4: string) => number): void" },
-    { marker: "5", text: "foo5(x: number, callback: (y5: string) => number): void" },
+    { marker: "5", text: "callback(y5: string): number" },
 );
 
 goTo.marker('6');

tests/cases/fourslash/genericFunctionSignatureHelp3.ts

@@ -26,9 +26,9 @@
 verify.signatureHelp(
     { marker: "1", text: "foo1(x: number, callback: (y1: {}) => number): void" },
     { marker: "2", text: "foo2(x: number, callback: (y2: {}) => number): void" },
-    { marker: "3", text: "foo3(x: number, callback: (y3: {}) => number): void" },
+    { marker: "3", text: "callback(y3: {}): number" },
     { marker: "4", text: "foo4(x: number, callback: (y4: string) => number): void" },
-    { marker: "5", text: "foo5(x: number, callback: (y5: string) => number): void" },
+    { marker: "5", text: "callback(y5: string): number" },
 );
 
 goTo.marker('6');

tests/cases/fourslash/genericFunctionSignatureHelp3MultiFile.ts

@@ -0,0 +1,82 @@
+/// <reference path='fourslash.ts' />
+
+////interface I {
+////    m(n: number, s: string): void;
+////    m2: () => void;
+////}
+////declare function takesObj(i: I): void;
+////takesObj({ m: (/*takesObj0*/) });
+////takesObj({ m(/*takesObj1*/) });
+////takesObj({ m: function(/*takesObj2*/) });
+////takesObj({ m2: (/*takesObj3*/) });
+////
+////declare function takesCb(cb: (n: number, s: string, b: boolean) => void): void;
+////takesCb((/*contextualParameter1*/));
+////takesCb((/*contextualParameter1b*/) => {});
+////takesCb((n, /*contextualParameter2*/));
+////takesCb((n, s, /*contextualParameter3*/));
+////takesCb((n,/*contextualParameter3_2*/ s, b));
+////takesCb((n, s, b, /*contextualParameter4*/));
+////
+////type Cb = () => void;
+////const cb: Cb = (/*contextualTypeAlias*/)
+////
+////const cb2: () => void = (/*contextualFunctionType*/)
+
+verify.signatureHelp(
+    {
+        marker: ["takesObj0", "takesObj1", "takesObj2"],
+        text: "m(n: number, s: string): void",
+        parameterCount: 2,
+        parameterName: "n",
+        parameterSpan: "n: number",
+    },
+    {
+        marker: "takesObj3",
+        text: "m2(): void",
+        parameterCount: 0,
+    },
+    {
+        marker: ["contextualParameter1", "contextualParameter1b"],
+        text: "cb(n: number, s: string, b: boolean): void",
+        parameterCount: 3,
+        parameterName: "n",
+        parameterSpan: "n: number",
+    },
+    {
+        marker: "contextualParameter2",
+        text: "cb(n: number, s: string, b: boolean): void",
+        parameterCount: 3,
+        parameterName: "s",
+        parameterSpan: "s: string",
+    },
+    {
+        marker: "contextualParameter3",
+        text: "cb(n: number, s: string, b: boolean): void",
+        parameterCount: 3,
+        parameterName: "b",
+        parameterSpan: "b: boolean",
+    },
+    {
+        marker: "contextualParameter3_2",
+        text: "cb(n: number, s: string, b: boolean): void",
+        parameterCount: 3,
+        parameterName: "s",
+        parameterSpan: "s: string",
+    },
+    {
+        marker: "contextualParameter4",
+        text: "cb(n: number, s: string, b: boolean): void",
+        parameterCount: 3,
+    },
+    {
+        marker: "contextualTypeAlias",
+        text: "Cb(): void",
+        parameterCount: 0,
+    },
+    {
+        marker: "contextualFunctionType",
+        text: "cb2(): void",
+        parameterCount: 0,
+    },
+);