Merge pull request #7298 from Microsoft/contextually-type-binding-initializers

Contextually type binding initializers

src/compiler/checker.ts

@@ -2604,7 +2604,7 @@ namespace ts {
             return name.kind === SyntaxKind.ComputedPropertyName && !isStringOrNumericLiteral((<ComputedPropertyName>name).expression.kind);
         }
 
-        // Return the inferred type for a binding element
+        /** Return the inferred type for a binding element */
         function getTypeForBindingElement(declaration: BindingElement): Type {
             const pattern = <BindingPattern>declaration.parent;
             const parentType = getTypeForBindingElementParent(<VariableLikeDeclaration>pattern.parent);
@@ -2630,6 +2630,9 @@ namespace ts {
                     // computed properties with non-literal names are treated as 'any'
                     return anyType;
                 }
+                if (declaration.initializer) {
+                    getContextualType(declaration.initializer);
+                }
 
                 // Use type of the specified property, or otherwise, for a numeric name, the type of the numeric index signature,
                 // or otherwise the type of the string index signature.
@@ -7825,11 +7828,14 @@ namespace ts {
             return undefined;
         }
 
-        // In a variable, parameter or property declaration with a type annotation, the contextual type of an initializer
-        // expression is the type of the variable, parameter or property. Otherwise, in a parameter declaration of a
-        // contextually typed function expression, the contextual type of an initializer expression is the contextual type
-        // of the parameter. Otherwise, in a variable or parameter declaration with a binding pattern name, the contextual
-        // type of an initializer expression is the type implied by the binding pattern.
+        // In a variable, parameter or property declaration with a type annotation,
+        //   the contextual type of an initializer expression is the type of the variable, parameter or property. 
+        // Otherwise, in a parameter declaration of a contextually typed function expression, 
+        //   the contextual type of an initializer expression is the contextual type of the parameter. 
+        // Otherwise, in a variable or parameter declaration with a binding pattern name,
+        //   the contextual type of an initializer expression is the type implied by the binding pattern.
+        // Otherwise, in a binding pattern inside a variable or parameter declaration,
+        //   the contextual type of an initializer expression is the type annotation of the containing declaration, if present.
         function getContextualTypeForInitializerExpression(node: Expression): Type {
             const declaration = <VariableLikeDeclaration>node.parent;
             if (node === declaration.initializer) {
@@ -7845,6 +7851,18 @@ namespace ts {
                 if (isBindingPattern(declaration.name)) {
                     return getTypeFromBindingPattern(<BindingPattern>declaration.name, /*includePatternInType*/ true);
                 }
+                if (isBindingPattern(declaration.parent)) {
+                    const parentDeclaration = declaration.parent.parent;
+                    const name = declaration.propertyName || declaration.name;
+                    if (isVariableLike(parentDeclaration) &&
+                        parentDeclaration.type &&
+                        !isBindingPattern(name)) {
+                        const text = getTextOfPropertyName(name);
+                        if (text) {
+                            return getTypeOfPropertyOfType(getTypeFromTypeNode(parentDeclaration.type), text);
+                        }
+                    }
+                }
             }
             return undefined;
         }

tests/baselines/reference/contextuallyTypedBindingInitializer.js

@@ -0,0 +1,51 @@
+//// [contextuallyTypedBindingInitializer.ts]
+interface Show {
+    show: (x: number) => string;
+}
+function f({ show = v => v.toString() }: Show) {}
+function f2({ "show": showRename = v => v.toString() }: Show) {}
+function f3({ ["show"]: showRename = v => v.toString() }: Show) {}
+
+interface Nested {
+    nested: Show
+}
+function ff({ nested = { show: v => v.toString() } }: Nested) {}
+
+interface Tuples {
+    prop: [string, number];
+}
+function g({ prop = ["hello", 1234] }: Tuples) {}
+
+interface StringUnion {
+    prop: "foo" | "bar";
+}
+function h({ prop = "foo" }: StringUnion) {}
+
+interface StringIdentity {
+    stringIdentity(s: string): string;
+}
+let { stringIdentity: id = arg => arg }: StringIdentity = { stringIdentity: x => x};
+
+
+
+
+//// [contextuallyTypedBindingInitializer.js]
+function f(_a) {
+    var _b = _a.show, show = _b === void 0 ? function (v) { return v.toString(); } : _b;
+}
+function f2(_a) {
+    var _b = _a["show"], showRename = _b === void 0 ? function (v) { return v.toString(); } : _b;
+}
+function f3(_a) {
+    var _b = "show", _c = _a[_b], showRename = _c === void 0 ? function (v) { return v.toString(); } : _c;
+}
+function ff(_a) {
+    var _b = _a.nested, nested = _b === void 0 ? { show: function (v) { return v.toString(); } } : _b;
+}
+function g(_a) {
+    var _b = _a.prop, prop = _b === void 0 ? ["hello", 1234] : _b;
+}
+function h(_a) {
+    var _b = _a.prop, prop = _b === void 0 ? "foo" : _b;
+}
+var _a = { stringIdentity: function (x) { return x; } }.stringIdentity, id = _a === void 0 ? function (arg) { return arg; } : _a;

tests/baselines/reference/contextuallyTypedBindingInitializer.symbols

@@ -0,0 +1,93 @@
+=== tests/cases/conformance/types/contextualTypes/methodDeclarations/contextuallyTypedBindingInitializer.ts ===
+interface Show {
+>Show : Symbol(Show, Decl(contextuallyTypedBindingInitializer.ts, 0, 0))
+
+    show: (x: number) => string;
+>show : Symbol(show, Decl(contextuallyTypedBindingInitializer.ts, 0, 16))
+>x : Symbol(x, Decl(contextuallyTypedBindingInitializer.ts, 1, 11))
+}
+function f({ show = v => v.toString() }: Show) {}
+>f : Symbol(f, Decl(contextuallyTypedBindingInitializer.ts, 2, 1))
+>show : Symbol(show, Decl(contextuallyTypedBindingInitializer.ts, 3, 12))
+>v : Symbol(v, Decl(contextuallyTypedBindingInitializer.ts, 3, 19))
+>v.toString : Symbol(Number.toString, Decl(lib.d.ts, --, --))
+>v : Symbol(v, Decl(contextuallyTypedBindingInitializer.ts, 3, 19))
+>toString : Symbol(Number.toString, Decl(lib.d.ts, --, --))
+>Show : Symbol(Show, Decl(contextuallyTypedBindingInitializer.ts, 0, 0))
+
+function f2({ "show": showRename = v => v.toString() }: Show) {}
+>f2 : Symbol(f2, Decl(contextuallyTypedBindingInitializer.ts, 3, 49))
+>showRename : Symbol(showRename, Decl(contextuallyTypedBindingInitializer.ts, 4, 13))
+>v : Symbol(v, Decl(contextuallyTypedBindingInitializer.ts, 4, 34))
+>v.toString : Symbol(Number.toString, Decl(lib.d.ts, --, --))
+>v : Symbol(v, Decl(contextuallyTypedBindingInitializer.ts, 4, 34))
+>toString : Symbol(Number.toString, Decl(lib.d.ts, --, --))
+>Show : Symbol(Show, Decl(contextuallyTypedBindingInitializer.ts, 0, 0))
+
+function f3({ ["show"]: showRename = v => v.toString() }: Show) {}
+>f3 : Symbol(f3, Decl(contextuallyTypedBindingInitializer.ts, 4, 64))
+>showRename : Symbol(showRename, Decl(contextuallyTypedBindingInitializer.ts, 5, 13))
+>v : Symbol(v, Decl(contextuallyTypedBindingInitializer.ts, 5, 36))
+>v.toString : Symbol(Number.toString, Decl(lib.d.ts, --, --))
+>v : Symbol(v, Decl(contextuallyTypedBindingInitializer.ts, 5, 36))
+>toString : Symbol(Number.toString, Decl(lib.d.ts, --, --))
+>Show : Symbol(Show, Decl(contextuallyTypedBindingInitializer.ts, 0, 0))
+
+interface Nested {
+>Nested : Symbol(Nested, Decl(contextuallyTypedBindingInitializer.ts, 5, 66))
+
+    nested: Show
+>nested : Symbol(nested, Decl(contextuallyTypedBindingInitializer.ts, 7, 18))
+>Show : Symbol(Show, Decl(contextuallyTypedBindingInitializer.ts, 0, 0))
+}
+function ff({ nested = { show: v => v.toString() } }: Nested) {}
+>ff : Symbol(ff, Decl(contextuallyTypedBindingInitializer.ts, 9, 1))
+>nested : Symbol(nested, Decl(contextuallyTypedBindingInitializer.ts, 10, 13))
+>show : Symbol(show, Decl(contextuallyTypedBindingInitializer.ts, 10, 24))
+>v : Symbol(v, Decl(contextuallyTypedBindingInitializer.ts, 10, 30))
+>v.toString : Symbol(Number.toString, Decl(lib.d.ts, --, --))
+>v : Symbol(v, Decl(contextuallyTypedBindingInitializer.ts, 10, 30))
+>toString : Symbol(Number.toString, Decl(lib.d.ts, --, --))
+>Nested : Symbol(Nested, Decl(contextuallyTypedBindingInitializer.ts, 5, 66))
+
+interface Tuples {
+>Tuples : Symbol(Tuples, Decl(contextuallyTypedBindingInitializer.ts, 10, 64))
+
+    prop: [string, number];
+>prop : Symbol(prop, Decl(contextuallyTypedBindingInitializer.ts, 12, 18))
+}
+function g({ prop = ["hello", 1234] }: Tuples) {}
+>g : Symbol(g, Decl(contextuallyTypedBindingInitializer.ts, 14, 1))
+>prop : Symbol(prop, Decl(contextuallyTypedBindingInitializer.ts, 15, 12))
+>Tuples : Symbol(Tuples, Decl(contextuallyTypedBindingInitializer.ts, 10, 64))
+
+interface StringUnion {
+>StringUnion : Symbol(StringUnion, Decl(contextuallyTypedBindingInitializer.ts, 15, 49))
+
+    prop: "foo" | "bar";
+>prop : Symbol(prop, Decl(contextuallyTypedBindingInitializer.ts, 17, 23))
+}
+function h({ prop = "foo" }: StringUnion) {}
+>h : Symbol(h, Decl(contextuallyTypedBindingInitializer.ts, 19, 1))
+>prop : Symbol(prop, Decl(contextuallyTypedBindingInitializer.ts, 20, 12))
+>StringUnion : Symbol(StringUnion, Decl(contextuallyTypedBindingInitializer.ts, 15, 49))
+
+interface StringIdentity {
+>StringIdentity : Symbol(StringIdentity, Decl(contextuallyTypedBindingInitializer.ts, 20, 44))
+
+    stringIdentity(s: string): string;
+>stringIdentity : Symbol(stringIdentity, Decl(contextuallyTypedBindingInitializer.ts, 22, 26))
+>s : Symbol(s, Decl(contextuallyTypedBindingInitializer.ts, 23, 19))
+}
+let { stringIdentity: id = arg => arg }: StringIdentity = { stringIdentity: x => x};
+>stringIdentity : Symbol(StringIdentity.stringIdentity, Decl(contextuallyTypedBindingInitializer.ts, 22, 26))
+>id : Symbol(id, Decl(contextuallyTypedBindingInitializer.ts, 25, 5))
+>arg : Symbol(arg, Decl(contextuallyTypedBindingInitializer.ts, 25, 26))
+>arg : Symbol(arg, Decl(contextuallyTypedBindingInitializer.ts, 25, 26))
+>StringIdentity : Symbol(StringIdentity, Decl(contextuallyTypedBindingInitializer.ts, 20, 44))
+>stringIdentity : Symbol(stringIdentity, Decl(contextuallyTypedBindingInitializer.ts, 25, 59))
+>x : Symbol(x, Decl(contextuallyTypedBindingInitializer.ts, 25, 75))
+>x : Symbol(x, Decl(contextuallyTypedBindingInitializer.ts, 25, 75))
+
+
+

tests/baselines/reference/contextuallyTypedBindingInitializer.types

@@ -0,0 +1,110 @@
+=== tests/cases/conformance/types/contextualTypes/methodDeclarations/contextuallyTypedBindingInitializer.ts ===
+interface Show {
+>Show : Show
+
+    show: (x: number) => string;
+>show : (x: number) => string
+>x : number
+}
+function f({ show = v => v.toString() }: Show) {}
+>f : ({show}: Show) => void
+>show : (x: number) => string
+>v => v.toString() : (v: number) => string
+>v : number
+>v.toString() : string
+>v.toString : (radix?: number) => string
+>v : number
+>toString : (radix?: number) => string
+>Show : Show
+
+function f2({ "show": showRename = v => v.toString() }: Show) {}
+>f2 : ({"show": showRename}: Show) => void
+>showRename : (x: number) => string
+>v => v.toString() : (v: number) => string
+>v : number
+>v.toString() : string
+>v.toString : (radix?: number) => string
+>v : number
+>toString : (radix?: number) => string
+>Show : Show
+
+function f3({ ["show"]: showRename = v => v.toString() }: Show) {}
+>f3 : ({["show"]: showRename}: Show) => void
+>"show" : string
+>showRename : (x: number) => string
+>v => v.toString() : (v: number) => string
+>v : number
+>v.toString() : string
+>v.toString : (radix?: number) => string
+>v : number
+>toString : (radix?: number) => string
+>Show : Show
+
+interface Nested {
+>Nested : Nested
+
+    nested: Show
+>nested : Show
+>Show : Show
+}
+function ff({ nested = { show: v => v.toString() } }: Nested) {}
+>ff : ({nested}: Nested) => void
+>nested : Show
+>{ show: v => v.toString() } : { show: (v: number) => string; }
+>show : (v: number) => string
+>v => v.toString() : (v: number) => string
+>v : number
+>v.toString() : string
+>v.toString : (radix?: number) => string
+>v : number
+>toString : (radix?: number) => string
+>Nested : Nested
+
+interface Tuples {
+>Tuples : Tuples
+
+    prop: [string, number];
+>prop : [string, number]
+}
+function g({ prop = ["hello", 1234] }: Tuples) {}
+>g : ({prop}: Tuples) => void
+>prop : [string, number]
+>["hello", 1234] : [string, number]
+>"hello" : string
+>1234 : number
+>Tuples : Tuples
+
+interface StringUnion {
+>StringUnion : StringUnion
+
+    prop: "foo" | "bar";
+>prop : "foo" | "bar"
+}
+function h({ prop = "foo" }: StringUnion) {}
+>h : ({prop}: StringUnion) => void
+>prop : "foo" | "bar"
+>"foo" : "foo"
+>StringUnion : StringUnion
+
+interface StringIdentity {
+>StringIdentity : StringIdentity
+
+    stringIdentity(s: string): string;
+>stringIdentity : (s: string) => string
+>s : string
+}
+let { stringIdentity: id = arg => arg }: StringIdentity = { stringIdentity: x => x};
+>stringIdentity : any
+>id : (s: string) => string
+>arg => arg : (arg: string) => string
+>arg : string
+>arg : string
+>StringIdentity : StringIdentity
+>{ stringIdentity: x => x} : { stringIdentity: (x: string) => string; }
+>stringIdentity : (x: string) => string
+>x => x : (x: string) => string
+>x : string
+>x : string
+
+
+

tests/baselines/reference/contextuallyTypedBindingInitializerNegative.errors.txt

@@ -0,0 +1,71 @@
+tests/cases/conformance/types/contextualTypes/methodDeclarations/contextuallyTypedBindingInitializerNegative.ts(4,20): error TS2322: Type '(v: number) => number' is not assignable to type '(x: number) => string'.
+  Type 'number' is not assignable to type 'string'.
+tests/cases/conformance/types/contextualTypes/methodDeclarations/contextuallyTypedBindingInitializerNegative.ts(5,23): error TS2322: Type '(v: number) => number' is not assignable to type '(x: number) => string'.
+  Type 'number' is not assignable to type 'string'.
+tests/cases/conformance/types/contextualTypes/methodDeclarations/contextuallyTypedBindingInitializerNegative.ts(6,25): error TS2322: Type '(v: number) => number' is not assignable to type '(x: number) => string'.
+  Type 'number' is not assignable to type 'string'.
+tests/cases/conformance/types/contextualTypes/methodDeclarations/contextuallyTypedBindingInitializerNegative.ts(11,23): error TS2322: Type '{ show: (v: number) => number; }' is not assignable to type 'Show'.
+  Types of property 'show' are incompatible.
+    Type '(v: number) => number' is not assignable to type '(x: number) => string'.
+      Type 'number' is not assignable to type 'string'.
+tests/cases/conformance/types/contextualTypes/methodDeclarations/contextuallyTypedBindingInitializerNegative.ts(16,23): error TS2322: Type '(arg: string) => number' is not assignable to type '(s: string) => string'.
+  Type 'number' is not assignable to type 'string'.
+tests/cases/conformance/types/contextualTypes/methodDeclarations/contextuallyTypedBindingInitializerNegative.ts(21,14): error TS2322: Type '[number, number]' is not assignable to type '[string, number]'.
+  Types of property '0' are incompatible.
+    Type 'number' is not assignable to type 'string'.
+tests/cases/conformance/types/contextualTypes/methodDeclarations/contextuallyTypedBindingInitializerNegative.ts(26,14): error TS2322: Type '"baz"' is not assignable to type '"foo" | "bar"'.
+  Type '"baz"' is not assignable to type '"bar"'.
+
+
+==== tests/cases/conformance/types/contextualTypes/methodDeclarations/contextuallyTypedBindingInitializerNegative.ts (7 errors) ====
+    interface Show {
+        show: (x: number) => string;
+    }
+    function f({ show: showRename = v => v }: Show) {}
+                       ~~~~~~~~~~
+!!! error TS2322: Type '(v: number) => number' is not assignable to type '(x: number) => string'.
+!!! error TS2322:   Type 'number' is not assignable to type 'string'.
+    function f2({ "show": showRename = v => v }: Show) {}
+                          ~~~~~~~~~~
+!!! error TS2322: Type '(v: number) => number' is not assignable to type '(x: number) => string'.
+!!! error TS2322:   Type 'number' is not assignable to type 'string'.
+    function f3({ ["show"]: showRename = v => v }: Show) {}
+                            ~~~~~~~~~~
+!!! error TS2322: Type '(v: number) => number' is not assignable to type '(x: number) => string'.
+!!! error TS2322:   Type 'number' is not assignable to type 'string'.
+    
+    interface Nested {
+        nested: Show
+    }
+    function ff({ nested: nestedRename = { show: v => v } }: Nested) {}
+                          ~~~~~~~~~~~~
+!!! error TS2322: Type '{ show: (v: number) => number; }' is not assignable to type 'Show'.
+!!! error TS2322:   Types of property 'show' are incompatible.
+!!! error TS2322:     Type '(v: number) => number' is not assignable to type '(x: number) => string'.
+!!! error TS2322:       Type 'number' is not assignable to type 'string'.
+    
+    interface StringIdentity {
+        stringIdentity(s: string): string;
+    }
+    let { stringIdentity: id = arg => arg.length }: StringIdentity = { stringIdentity: x => x};
+                          ~~
+!!! error TS2322: Type '(arg: string) => number' is not assignable to type '(s: string) => string'.
+!!! error TS2322:   Type 'number' is not assignable to type 'string'.
+    
+    interface Tuples {
+        prop: [string, number];
+    }
+    function g({ prop = [101, 1234] }: Tuples) {}
+                 ~~~~
+!!! error TS2322: Type '[number, number]' is not assignable to type '[string, number]'.
+!!! error TS2322:   Types of property '0' are incompatible.
+!!! error TS2322:     Type 'number' is not assignable to type 'string'.
+    
+    interface StringUnion {
+        prop: "foo" | "bar";
+    }
+    function h({ prop = "baz" }: StringUnion) {}
+                 ~~~~
+!!! error TS2322: Type '"baz"' is not assignable to type '"foo" | "bar"'.
+!!! error TS2322:   Type '"baz"' is not assignable to type '"bar"'.
+    

tests/baselines/reference/contextuallyTypedBindingInitializerNegative.js

@@ -0,0 +1,49 @@
+//// [contextuallyTypedBindingInitializerNegative.ts]
+interface Show {
+    show: (x: number) => string;
+}
+function f({ show: showRename = v => v }: Show) {}
+function f2({ "show": showRename = v => v }: Show) {}
+function f3({ ["show"]: showRename = v => v }: Show) {}
+
+interface Nested {
+    nested: Show
+}
+function ff({ nested: nestedRename = { show: v => v } }: Nested) {}
+
+interface StringIdentity {
+    stringIdentity(s: string): string;
+}
+let { stringIdentity: id = arg => arg.length }: StringIdentity = { stringIdentity: x => x};
+
+interface Tuples {
+    prop: [string, number];
+}
+function g({ prop = [101, 1234] }: Tuples) {}
+
+interface StringUnion {
+    prop: "foo" | "bar";
+}
+function h({ prop = "baz" }: StringUnion) {}
+
+
+//// [contextuallyTypedBindingInitializerNegative.js]
+function f(_a) {
+    var _b = _a.show, showRename = _b === void 0 ? function (v) { return v; } : _b;
+}
+function f2(_a) {
+    var _b = _a["show"], showRename = _b === void 0 ? function (v) { return v; } : _b;
+}
+function f3(_a) {
+    var _b = "show", _c = _a[_b], showRename = _c === void 0 ? function (v) { return v; } : _c;
+}
+function ff(_a) {
+    var _b = _a.nested, nestedRename = _b === void 0 ? { show: function (v) { return v; } } : _b;
+}
+var _a = { stringIdentity: function (x) { return x; } }.stringIdentity, id = _a === void 0 ? function (arg) { return arg.length; } : _a;
+function g(_a) {
+    var _b = _a.prop, prop = _b === void 0 ? [101, 1234] : _b;
+}
+function h(_a) {
+    var _b = _a.prop, prop = _b === void 0 ? "baz" : _b;
+}

tests/cases/conformance/types/contextualTypes/methodDeclarations/contextuallyTypedBindingInitializer.ts

@@ -0,0 +1,29 @@
+// @noImplicitAny: true
+interface Show {
+    show: (x: number) => string;
+}
+function f({ show = v => v.toString() }: Show) {}
+function f2({ "show": showRename = v => v.toString() }: Show) {}
+function f3({ ["show"]: showRename = v => v.toString() }: Show) {}
+
+interface Nested {
+    nested: Show
+}
+function ff({ nested = { show: v => v.toString() } }: Nested) {}
+
+interface Tuples {
+    prop: [string, number];
+}
+function g({ prop = ["hello", 1234] }: Tuples) {}
+
+interface StringUnion {
+    prop: "foo" | "bar";
+}
+function h({ prop = "foo" }: StringUnion) {}
+
+interface StringIdentity {
+    stringIdentity(s: string): string;
+}
+let { stringIdentity: id = arg => arg }: StringIdentity = { stringIdentity: x => x};
+
+

tests/cases/conformance/types/contextualTypes/methodDeclarations/contextuallyTypedBindingInitializerNegative.ts

@@ -0,0 +1,27 @@
+// @noImplicitAny: true
+interface Show {
+    show: (x: number) => string;
+}
+function f({ show: showRename = v => v }: Show) {}
+function f2({ "show": showRename = v => v }: Show) {}
+function f3({ ["show"]: showRename = v => v }: Show) {}
+
+interface Nested {
+    nested: Show
+}
+function ff({ nested: nestedRename = { show: v => v } }: Nested) {}
+
+interface StringIdentity {
+    stringIdentity(s: string): string;
+}
+let { stringIdentity: id = arg => arg.length }: StringIdentity = { stringIdentity: x => x};
+
+interface Tuples {
+    prop: [string, number];
+}
+function g({ prop = [101, 1234] }: Tuples) {}
+
+interface StringUnion {
+    prop: "foo" | "bar";
+}
+function h({ prop = "baz" }: StringUnion) {}