Include type parameter defaults in contextual typing (#50994)

* Include type parameter defaults in contextual typing

* Add tests

* Add additional an test for instantiating contextual signature using default type param (#51002)

* Update comment

Co-authored-by: Mateusz Burzyński <mateuszburzynski@gmail.com>

src/compiler/checker.ts

@@ -27596,9 +27596,10 @@ namespace ts {
         function instantiateContextualType(contextualType: Type | undefined, node: Node, contextFlags: ContextFlags | undefined): Type | undefined {
             if (contextualType && maybeTypeOfKind(contextualType, TypeFlags.Instantiable)) {
                 const inferenceContext = getInferenceContext(node);
-                // If no inferences have been made, nothing is gained from instantiating as type parameters
-                // would just be replaced with their defaults similar to the apparent type.
-                if (inferenceContext && contextFlags! & ContextFlags.Signature && some(inferenceContext.inferences, hasInferenceCandidates)) {
+                // If no inferences have been made, and none of the type parameters for which we are inferring
+                // specify default types, nothing is gained from instantiating as type parameters would just be
+                // replaced with their constraints similar to the apparent type.
+                if (inferenceContext && contextFlags! & ContextFlags.Signature && some(inferenceContext.inferences, hasInferenceCandidatesOrDefault)) {
                     // For contextual signatures we incorporate all inferences made so far, e.g. from return
                     // types as well as arguments to the left in a function call.
                     return instantiateInstantiableTypes(contextualType, inferenceContext.nonFixingMapper);
@@ -35209,6 +35210,10 @@ namespace ts {
             return !!(info.candidates || info.contraCandidates);
         }
 
+        function hasInferenceCandidatesOrDefault(info: InferenceInfo) {
+            return !!(info.candidates || info.contraCandidates || hasTypeParameterDefault(info.typeParameter));
+        }
+
         function hasOverlappingInferences(a: InferenceInfo[], b: InferenceInfo[]) {
             for (let i = 0; i < a.length; i++) {
                 if (hasInferenceCandidates(a[i]) && hasInferenceCandidates(b[i])) {

tests/baselines/reference/contextualSignatureConditionalTypeInstantiationUsingDefault.symbols

@@ -0,0 +1,67 @@
+=== tests/cases/compiler/contextualSignatureConditionalTypeInstantiationUsingDefault.ts ===
+// repro #46310
+
+export interface TypegenDisabled {
+>TypegenDisabled : Symbol(TypegenDisabled, Decl(contextualSignatureConditionalTypeInstantiationUsingDefault.ts, 0, 0))
+
+  "@@xstate/typegen": false;
+>"@@xstate/typegen" : Symbol(TypegenDisabled["@@xstate/typegen"], Decl(contextualSignatureConditionalTypeInstantiationUsingDefault.ts, 2, 34))
+}
+export interface TypegenEnabled {
+>TypegenEnabled : Symbol(TypegenEnabled, Decl(contextualSignatureConditionalTypeInstantiationUsingDefault.ts, 4, 1))
+
+  "@@xstate/typegen": true;
+>"@@xstate/typegen" : Symbol(TypegenEnabled["@@xstate/typegen"], Decl(contextualSignatureConditionalTypeInstantiationUsingDefault.ts, 5, 33))
+}
+
+type ActionFunction<TEvent extends { type: string }> = (event: TEvent) => void;
+>ActionFunction : Symbol(ActionFunction, Decl(contextualSignatureConditionalTypeInstantiationUsingDefault.ts, 7, 1))
+>TEvent : Symbol(TEvent, Decl(contextualSignatureConditionalTypeInstantiationUsingDefault.ts, 9, 20))
+>type : Symbol(type, Decl(contextualSignatureConditionalTypeInstantiationUsingDefault.ts, 9, 36))
+>event : Symbol(event, Decl(contextualSignatureConditionalTypeInstantiationUsingDefault.ts, 9, 56))
+>TEvent : Symbol(TEvent, Decl(contextualSignatureConditionalTypeInstantiationUsingDefault.ts, 9, 20))
+
+declare function createMachine<
+>createMachine : Symbol(createMachine, Decl(contextualSignatureConditionalTypeInstantiationUsingDefault.ts, 9, 79))
+
+  TTypesMeta extends TypegenEnabled | TypegenDisabled = TypegenDisabled
+>TTypesMeta : Symbol(TTypesMeta, Decl(contextualSignatureConditionalTypeInstantiationUsingDefault.ts, 11, 31))
+>TypegenEnabled : Symbol(TypegenEnabled, Decl(contextualSignatureConditionalTypeInstantiationUsingDefault.ts, 4, 1))
+>TypegenDisabled : Symbol(TypegenDisabled, Decl(contextualSignatureConditionalTypeInstantiationUsingDefault.ts, 0, 0))
+>TypegenDisabled : Symbol(TypegenDisabled, Decl(contextualSignatureConditionalTypeInstantiationUsingDefault.ts, 0, 0))
+
+>(
+  config: {
+>config : Symbol(config, Decl(contextualSignatureConditionalTypeInstantiationUsingDefault.ts, 13, 2))
+
+    types?: TTypesMeta;
+>types : Symbol(types, Decl(contextualSignatureConditionalTypeInstantiationUsingDefault.ts, 14, 11))
+>TTypesMeta : Symbol(TTypesMeta, Decl(contextualSignatureConditionalTypeInstantiationUsingDefault.ts, 11, 31))
+
+  },
+  implementations: TTypesMeta extends TypegenEnabled
+>implementations : Symbol(implementations, Decl(contextualSignatureConditionalTypeInstantiationUsingDefault.ts, 16, 4))
+>TTypesMeta : Symbol(TTypesMeta, Decl(contextualSignatureConditionalTypeInstantiationUsingDefault.ts, 11, 31))
+>TypegenEnabled : Symbol(TypegenEnabled, Decl(contextualSignatureConditionalTypeInstantiationUsingDefault.ts, 4, 1))
+
+    ? ActionFunction<{ type: "test" }>
+>ActionFunction : Symbol(ActionFunction, Decl(contextualSignatureConditionalTypeInstantiationUsingDefault.ts, 7, 1))
+>type : Symbol(type, Decl(contextualSignatureConditionalTypeInstantiationUsingDefault.ts, 18, 22))
+
+    : ActionFunction<{ type: string }>
+>ActionFunction : Symbol(ActionFunction, Decl(contextualSignatureConditionalTypeInstantiationUsingDefault.ts, 7, 1))
+>type : Symbol(type, Decl(contextualSignatureConditionalTypeInstantiationUsingDefault.ts, 19, 22))
+
+): void;
+
+createMachine({}, (ev) => {
+>createMachine : Symbol(createMachine, Decl(contextualSignatureConditionalTypeInstantiationUsingDefault.ts, 9, 79))
+>ev : Symbol(ev, Decl(contextualSignatureConditionalTypeInstantiationUsingDefault.ts, 22, 19))
+
+  ev.type; // should be `string`
+>ev.type : Symbol(type, Decl(contextualSignatureConditionalTypeInstantiationUsingDefault.ts, 19, 22))
+>ev : Symbol(ev, Decl(contextualSignatureConditionalTypeInstantiationUsingDefault.ts, 22, 19))
+>type : Symbol(type, Decl(contextualSignatureConditionalTypeInstantiationUsingDefault.ts, 19, 22))
+
+});
+

tests/baselines/reference/contextualSignatureConditionalTypeInstantiationUsingDefault.types

@@ -0,0 +1,56 @@
+=== tests/cases/compiler/contextualSignatureConditionalTypeInstantiationUsingDefault.ts ===
+// repro #46310
+
+export interface TypegenDisabled {
+  "@@xstate/typegen": false;
+>"@@xstate/typegen" : false
+>false : false
+}
+export interface TypegenEnabled {
+  "@@xstate/typegen": true;
+>"@@xstate/typegen" : true
+>true : true
+}
+
+type ActionFunction<TEvent extends { type: string }> = (event: TEvent) => void;
+>ActionFunction : ActionFunction<TEvent>
+>type : string
+>event : TEvent
+
+declare function createMachine<
+>createMachine : <TTypesMeta extends TypegenDisabled | TypegenEnabled = TypegenDisabled>(config: {    types?: TTypesMeta;}, implementations: TTypesMeta extends TypegenEnabled ? ActionFunction<{    type: "test";}> : ActionFunction<{    type: string;}>) => void
+
+  TTypesMeta extends TypegenEnabled | TypegenDisabled = TypegenDisabled
+>(
+  config: {
+>config : { types?: TTypesMeta | undefined; }
+
+    types?: TTypesMeta;
+>types : TTypesMeta | undefined
+
+  },
+  implementations: TTypesMeta extends TypegenEnabled
+>implementations : TTypesMeta extends TypegenEnabled ? ActionFunction<{ type: "test"; }> : ActionFunction<{ type: string; }>
+
+    ? ActionFunction<{ type: "test" }>
+>type : "test"
+
+    : ActionFunction<{ type: string }>
+>type : string
+
+): void;
+
+createMachine({}, (ev) => {
+>createMachine({}, (ev) => {  ev.type; // should be `string`}) : void
+>createMachine : <TTypesMeta extends TypegenDisabled | TypegenEnabled = TypegenDisabled>(config: { types?: TTypesMeta | undefined; }, implementations: TTypesMeta extends TypegenEnabled ? ActionFunction<{ type: "test"; }> : ActionFunction<{ type: string; }>) => void
+>{} : {}
+>(ev) => {  ev.type; // should be `string`} : (ev: { type: string; }) => void
+>ev : { type: string; }
+
+  ev.type; // should be `string`
+>ev.type : string
+>ev : { type: string; }
+>type : string
+
+});
+

tests/baselines/reference/genericInferenceDefaultTypeParameter.js

@@ -0,0 +1,21 @@
+//// [genericInferenceDefaultTypeParameter.ts]
+// Repro from #50858
+
+type Type = {
+    a: (e: string) => void;
+    b: (e: number) => void;
+}
+
+declare function f1<T extends keyof Type = "a">(props: Type[T]): void;
+
+f1(event => { });
+f1<"a">(event => { });
+f1<"b">(event => { });
+
+
+//// [genericInferenceDefaultTypeParameter.js]
+"use strict";
+// Repro from #50858
+f1(function (event) { });
+f1(function (event) { });
+f1(function (event) { });

tests/baselines/reference/genericInferenceDefaultTypeParameter.symbols

@@ -0,0 +1,35 @@
+=== tests/cases/compiler/genericInferenceDefaultTypeParameter.ts ===
+// Repro from #50858
+
+type Type = {
+>Type : Symbol(Type, Decl(genericInferenceDefaultTypeParameter.ts, 0, 0))
+
+    a: (e: string) => void;
+>a : Symbol(a, Decl(genericInferenceDefaultTypeParameter.ts, 2, 13))
+>e : Symbol(e, Decl(genericInferenceDefaultTypeParameter.ts, 3, 8))
+
+    b: (e: number) => void;
+>b : Symbol(b, Decl(genericInferenceDefaultTypeParameter.ts, 3, 27))
+>e : Symbol(e, Decl(genericInferenceDefaultTypeParameter.ts, 4, 8))
+}
+
+declare function f1<T extends keyof Type = "a">(props: Type[T]): void;
+>f1 : Symbol(f1, Decl(genericInferenceDefaultTypeParameter.ts, 5, 1))
+>T : Symbol(T, Decl(genericInferenceDefaultTypeParameter.ts, 7, 20))
+>Type : Symbol(Type, Decl(genericInferenceDefaultTypeParameter.ts, 0, 0))
+>props : Symbol(props, Decl(genericInferenceDefaultTypeParameter.ts, 7, 48))
+>Type : Symbol(Type, Decl(genericInferenceDefaultTypeParameter.ts, 0, 0))
+>T : Symbol(T, Decl(genericInferenceDefaultTypeParameter.ts, 7, 20))
+
+f1(event => { });
+>f1 : Symbol(f1, Decl(genericInferenceDefaultTypeParameter.ts, 5, 1))
+>event : Symbol(event, Decl(genericInferenceDefaultTypeParameter.ts, 9, 3))
+
+f1<"a">(event => { });
+>f1 : Symbol(f1, Decl(genericInferenceDefaultTypeParameter.ts, 5, 1))
+>event : Symbol(event, Decl(genericInferenceDefaultTypeParameter.ts, 10, 8))
+
+f1<"b">(event => { });
+>f1 : Symbol(f1, Decl(genericInferenceDefaultTypeParameter.ts, 5, 1))
+>event : Symbol(event, Decl(genericInferenceDefaultTypeParameter.ts, 11, 8))
+

tests/baselines/reference/genericInferenceDefaultTypeParameter.types

@@ -0,0 +1,37 @@
+=== tests/cases/compiler/genericInferenceDefaultTypeParameter.ts ===
+// Repro from #50858
+
+type Type = {
+>Type : { a: (e: string) => void; b: (e: number) => void; }
+
+    a: (e: string) => void;
+>a : (e: string) => void
+>e : string
+
+    b: (e: number) => void;
+>b : (e: number) => void
+>e : number
+}
+
+declare function f1<T extends keyof Type = "a">(props: Type[T]): void;
+>f1 : <T extends keyof Type = "a">(props: Type[T]) => void
+>props : Type[T]
+
+f1(event => { });
+>f1(event => { }) : void
+>f1 : <T extends keyof Type = "a">(props: Type[T]) => void
+>event => { } : (event: string) => void
+>event : string
+
+f1<"a">(event => { });
+>f1<"a">(event => { }) : void
+>f1 : <T extends keyof Type = "a">(props: Type[T]) => void
+>event => { } : (event: string) => void
+>event : string
+
+f1<"b">(event => { });
+>f1<"b">(event => { }) : void
+>f1 : <T extends keyof Type = "a">(props: Type[T]) => void
+>event => { } : (event: number) => void
+>event : number
+

tests/baselines/reference/genericInferenceDefaultTypeParameterJsxReact.js

@@ -0,0 +1,29 @@
+//// [genericInferenceDefaultTypeParameterJsxReact.tsx]
+/// <reference path="/.lib/react16.d.ts" />
+
+// Repro from #50858
+
+import React, { ComponentPropsWithRef, ElementType, ReactNode } from 'react';
+
+type ButtonBaseProps<T extends ElementType> = ComponentPropsWithRef<T> & { children?: ReactNode };
+
+function Component<T extends ElementType = 'span'>(props: ButtonBaseProps<T>) {
+    return <></>;
+}
+
+const v1 = <Component onClick={e => e.preventDefault()} />;
+
+
+//// [genericInferenceDefaultTypeParameterJsxReact.js]
+"use strict";
+/// <reference path="react16.d.ts" />
+var __importDefault = (this && this.__importDefault) || function (mod) {
+    return (mod && mod.__esModule) ? mod : { "default": mod };
+};
+exports.__esModule = true;
+// Repro from #50858
+var react_1 = __importDefault(require("react"));
+function Component(props) {
+    return react_1["default"].createElement(react_1["default"].Fragment, null);
+}
+var v1 = react_1["default"].createElement(Component, { onClick: function (e) { return e.preventDefault(); } });

tests/baselines/reference/genericInferenceDefaultTypeParameterJsxReact.symbols

@@ -0,0 +1,40 @@
+=== tests/cases/compiler/genericInferenceDefaultTypeParameterJsxReact.tsx ===
+/// <reference path="react16.d.ts" />
+
+// Repro from #50858
+
+import React, { ComponentPropsWithRef, ElementType, ReactNode } from 'react';
+>React : Symbol(React, Decl(genericInferenceDefaultTypeParameterJsxReact.tsx, 4, 6))
+>ComponentPropsWithRef : Symbol(ComponentPropsWithRef, Decl(genericInferenceDefaultTypeParameterJsxReact.tsx, 4, 15))
+>ElementType : Symbol(ElementType, Decl(genericInferenceDefaultTypeParameterJsxReact.tsx, 4, 38))
+>ReactNode : Symbol(ReactNode, Decl(genericInferenceDefaultTypeParameterJsxReact.tsx, 4, 51))
+
+type ButtonBaseProps<T extends ElementType> = ComponentPropsWithRef<T> & { children?: ReactNode };
+>ButtonBaseProps : Symbol(ButtonBaseProps, Decl(genericInferenceDefaultTypeParameterJsxReact.tsx, 4, 77))
+>T : Symbol(T, Decl(genericInferenceDefaultTypeParameterJsxReact.tsx, 6, 21))
+>ElementType : Symbol(ElementType, Decl(genericInferenceDefaultTypeParameterJsxReact.tsx, 4, 38))
+>ComponentPropsWithRef : Symbol(ComponentPropsWithRef, Decl(genericInferenceDefaultTypeParameterJsxReact.tsx, 4, 15))
+>T : Symbol(T, Decl(genericInferenceDefaultTypeParameterJsxReact.tsx, 6, 21))
+>children : Symbol(children, Decl(genericInferenceDefaultTypeParameterJsxReact.tsx, 6, 74))
+>ReactNode : Symbol(ReactNode, Decl(genericInferenceDefaultTypeParameterJsxReact.tsx, 4, 51))
+
+function Component<T extends ElementType = 'span'>(props: ButtonBaseProps<T>) {
+>Component : Symbol(Component, Decl(genericInferenceDefaultTypeParameterJsxReact.tsx, 6, 98))
+>T : Symbol(T, Decl(genericInferenceDefaultTypeParameterJsxReact.tsx, 8, 19))
+>ElementType : Symbol(ElementType, Decl(genericInferenceDefaultTypeParameterJsxReact.tsx, 4, 38))
+>props : Symbol(props, Decl(genericInferenceDefaultTypeParameterJsxReact.tsx, 8, 51))
+>ButtonBaseProps : Symbol(ButtonBaseProps, Decl(genericInferenceDefaultTypeParameterJsxReact.tsx, 4, 77))
+>T : Symbol(T, Decl(genericInferenceDefaultTypeParameterJsxReact.tsx, 8, 19))
+
+    return <></>;
+}
+
+const v1 = <Component onClick={e => e.preventDefault()} />;
+>v1 : Symbol(v1, Decl(genericInferenceDefaultTypeParameterJsxReact.tsx, 12, 5))
+>Component : Symbol(Component, Decl(genericInferenceDefaultTypeParameterJsxReact.tsx, 6, 98))
+>onClick : Symbol(onClick, Decl(genericInferenceDefaultTypeParameterJsxReact.tsx, 12, 21))
+>e : Symbol(e, Decl(genericInferenceDefaultTypeParameterJsxReact.tsx, 12, 31))
+>e.preventDefault : Symbol(React.SyntheticEvent.preventDefault, Decl(react16.d.ts, 642, 31))
+>e : Symbol(e, Decl(genericInferenceDefaultTypeParameterJsxReact.tsx, 12, 31))
+>preventDefault : Symbol(React.SyntheticEvent.preventDefault, Decl(react16.d.ts, 642, 31))
+

tests/baselines/reference/genericInferenceDefaultTypeParameterJsxReact.types

@@ -0,0 +1,35 @@
+=== tests/cases/compiler/genericInferenceDefaultTypeParameterJsxReact.tsx ===
+/// <reference path="react16.d.ts" />
+
+// Repro from #50858
+
+import React, { ComponentPropsWithRef, ElementType, ReactNode } from 'react';
+>React : typeof React
+>ComponentPropsWithRef : any
+>ElementType : any
+>ReactNode : any
+
+type ButtonBaseProps<T extends ElementType> = ComponentPropsWithRef<T> & { children?: ReactNode };
+>ButtonBaseProps : ButtonBaseProps<T>
+>children : React.ReactNode
+
+function Component<T extends ElementType = 'span'>(props: ButtonBaseProps<T>) {
+>Component : <T extends React.ElementType<any> = "span">(props: ButtonBaseProps<T>) => JSX.Element
+>props : ButtonBaseProps<T>
+
+    return <></>;
+><></> : JSX.Element
+}
+
+const v1 = <Component onClick={e => e.preventDefault()} />;
+>v1 : JSX.Element
+><Component onClick={e => e.preventDefault()} /> : JSX.Element
+>Component : <T extends React.ElementType<any> = "span">(props: ButtonBaseProps<T>) => JSX.Element
+>onClick : (e: React.MouseEvent<HTMLSpanElement>) => void
+>e => e.preventDefault() : (e: React.MouseEvent<HTMLSpanElement>) => void
+>e : React.MouseEvent<HTMLSpanElement>
+>e.preventDefault() : void
+>e.preventDefault : () => void
+>e : React.MouseEvent<HTMLSpanElement>
+>preventDefault : () => void
+

tests/cases/compiler/contextualSignatureConditionalTypeInstantiationUsingDefault.ts

@@ -0,0 +1,28 @@
+// @strict: true
+// @noEmit: true
+
+// repro #46310
+
+export interface TypegenDisabled {
+  "@@xstate/typegen": false;
+}
+export interface TypegenEnabled {
+  "@@xstate/typegen": true;
+}
+
+type ActionFunction<TEvent extends { type: string }> = (event: TEvent) => void;
+
+declare function createMachine<
+  TTypesMeta extends TypegenEnabled | TypegenDisabled = TypegenDisabled
+>(
+  config: {
+    types?: TTypesMeta;
+  },
+  implementations: TTypesMeta extends TypegenEnabled
+    ? ActionFunction<{ type: "test" }>
+    : ActionFunction<{ type: string }>
+): void;
+
+createMachine({}, (ev) => {
+  ev.type; // should be `string`
+});

tests/cases/compiler/genericInferenceDefaultTypeParameter.ts

@@ -0,0 +1,14 @@
+// @strict: true
+
+// Repro from #50858
+
+type Type = {
+    a: (e: string) => void;
+    b: (e: number) => void;
+}
+
+declare function f1<T extends keyof Type = "a">(props: Type[T]): void;
+
+f1(event => { });
+f1<"a">(event => { });
+f1<"b">(event => { });