Rest of untyped binding pattern is { [s: string]: any }

src/compiler/checker.ts

@@ -3309,14 +3309,19 @@ namespace ts {
         // Return the type implied by an object binding pattern
         function getTypeFromObjectBindingPattern(pattern: ObjectBindingPattern, includePatternInType: boolean, reportErrors: boolean): Type {
             const members = createMap<Symbol>();
+            let stringIndexInfo: IndexInfo;
             let hasComputedProperties = false;
             forEach(pattern.elements, e => {
                 const name = e.propertyName || <Identifier>e.name;
-                if (isComputedNonLiteralName(name) || e.dotDotDotToken) {
-                    // do not include computed properties or rests in the implied type
+                if (isComputedNonLiteralName(name)) {
+                    // do not include computed properties in the implied type
                     hasComputedProperties = true;
                     return;
                 }
+                if (e.dotDotDotToken) {
+                    stringIndexInfo = createIndexInfo(anyType, /*isReadonly*/ false);
+                    return;
+                }
 
                 const text = getTextOfPropertyName(name);
                 const flags = SymbolFlags.Property | SymbolFlags.Transient | (e.initializer ? SymbolFlags.Optional : 0);
@@ -3325,7 +3330,7 @@ namespace ts {
                 symbol.bindingElement = e;
                 members[symbol.name] = symbol;
             });
-            const result = createAnonymousType(undefined, members, emptyArray, emptyArray, undefined, undefined);
+            const result = createAnonymousType(undefined, members, emptyArray, emptyArray, stringIndexInfo, undefined);
             if (includePatternInType) {
                 result.pattern = pattern;
             }
@@ -11413,7 +11418,8 @@ namespace ts {
                         if (impliedProp) {
                             prop.flags |= impliedProp.flags & SymbolFlags.Optional;
                         }
-                        else if (!compilerOptions.suppressExcessPropertyErrors) {
+
+                        else if (!compilerOptions.suppressExcessPropertyErrors && !getIndexInfoOfType(contextualType, IndexKind.String)) {
                             error(memberDecl.name, Diagnostics.Object_literal_may_only_specify_known_properties_and_0_does_not_exist_in_type_1,
                                 symbolToString(member), typeToString(contextualType));
                         }

tests/baselines/reference/objectRest.js

@@ -36,6 +36,8 @@ let computed = 'b';
 let computed2 = 'a';
 var { [computed]: stillNotGreat, [computed2]: soSo,  ...o } = o;
 ({ [computed]: stillNotGreat, [computed2]: soSo, ...o } = o);
+
+var noContextualType = ({ aNumber = 12, ...notEmptyObject }) => aNumber + notEmptyObject['anythingGoes'];
 
 
 //// [objectRest.js]
@@ -76,4 +78,8 @@ let computed = 'b';
 let computed2 = 'a';
 var _g = computed, stillNotGreat = o[_g], _h = computed2, soSo = o[_h], o = __rest(o, [typeof _g === "symbol" ? _g : _g + "", typeof _h === "symbol" ? _h : _h + ""]);
 (_j = computed, stillNotGreat = o[_j], _k = computed2, soSo = o[_k], o = __rest(o, [typeof _j === "symbol" ? _j : _j + "", typeof _k === "symbol" ? _k : _k + ""]));
+var noContextualType = (_a) => {
+    var { aNumber = 12 } = _a, notEmptyObject = __rest(_a, ["aNumber"]);
+    return aNumber + notEmptyObject['anythingGoes'];
+};
 var _d, _f, _j, _k;

tests/baselines/reference/objectRest.symbols

@@ -169,3 +169,10 @@ var { [computed]: stillNotGreat, [computed2]: soSo,  ...o } = o;
 >o : Symbol(o, Decl(objectRest.ts, 0, 3), Decl(objectRest.ts, 35, 51))
 >o : Symbol(o, Decl(objectRest.ts, 0, 3), Decl(objectRest.ts, 35, 51))
 
+var noContextualType = ({ aNumber = 12, ...notEmptyObject }) => aNumber + notEmptyObject['anythingGoes'];
+>noContextualType : Symbol(noContextualType, Decl(objectRest.ts, 38, 3))
+>aNumber : Symbol(aNumber, Decl(objectRest.ts, 38, 25))
+>notEmptyObject : Symbol(notEmptyObject, Decl(objectRest.ts, 38, 39))
+>aNumber : Symbol(aNumber, Decl(objectRest.ts, 38, 25))
+>notEmptyObject : Symbol(notEmptyObject, Decl(objectRest.ts, 38, 39))
+

tests/baselines/reference/objectRest.types

@@ -195,3 +195,15 @@ var { [computed]: stillNotGreat, [computed2]: soSo,  ...o } = o;
 >o : { a: number; b: string; }
 >o : { a: number; b: string; }
 
+var noContextualType = ({ aNumber = 12, ...notEmptyObject }) => aNumber + notEmptyObject['anythingGoes'];
+>noContextualType : ({aNumber, ...notEmptyObject}: { [x: string]: any; aNumber?: number; }) => any
+>({ aNumber = 12, ...notEmptyObject }) => aNumber + notEmptyObject['anythingGoes'] : ({aNumber, ...notEmptyObject}: { [x: string]: any; aNumber?: number; }) => any
+>aNumber : number
+>12 : 12
+>notEmptyObject : { [x: string]: any; }
+>aNumber + notEmptyObject['anythingGoes'] : any
+>aNumber : number
+>notEmptyObject['anythingGoes'] : any
+>notEmptyObject : { [x: string]: any; }
+>'anythingGoes' : "anythingGoes"
+

tests/baselines/reference/objectRestNegative.errors.txt

@@ -3,11 +3,14 @@ tests/cases/conformance/types/rest/objectRestNegative.ts(6,10): error TS2322: Ty
   Types of property 'a' are incompatible.
     Type 'number' is not assignable to type 'string'.
 tests/cases/conformance/types/rest/objectRestNegative.ts(9,31): error TS2462: A rest element must be last in a destructuring pattern
+tests/cases/conformance/types/rest/objectRestNegative.ts(11,30): error TS7008: Member 'x' implicitly has an 'any' type.
+tests/cases/conformance/types/rest/objectRestNegative.ts(11,33): error TS7008: Member 'y' implicitly has an 'any' type.
 tests/cases/conformance/types/rest/objectRestNegative.ts(12,17): error TS2700: Rest types may only be created from object types.
 tests/cases/conformance/types/rest/objectRestNegative.ts(17,9): error TS2701: The target of an object rest assignment must be a variable or a property access.
+tests/cases/conformance/types/rest/objectRestNegative.ts(19,90): error TS2339: Property 'anythingGoes' does not exist on type '{ [x: string]: any; }'.
 
 
-==== tests/cases/conformance/types/rest/objectRestNegative.ts (5 errors) ====
+==== tests/cases/conformance/types/rest/objectRestNegative.ts (8 errors) ====
     let o = { a: 1, b: 'no' };
     var { ...mustBeLast, a } = o;
              ~~~~~~~~~~
@@ -27,6 +30,10 @@ tests/cases/conformance/types/rest/objectRestNegative.ts(17,9): error TS2701: Th
 !!! error TS2462: A rest element must be last in a destructuring pattern
     }
     function generic<T extends { x, y }>(t: T) {
+                                 ~~
+!!! error TS7008: Member 'x' implicitly has an 'any' type.
+                                    ~
+!!! error TS7008: Member 'y' implicitly has an 'any' type.
         let { x, ...rest } = t;
                     ~~~~
 !!! error TS2700: Rest types may only be created from object types.
@@ -37,4 +44,8 @@ tests/cases/conformance/types/rest/objectRestNegative.ts(17,9): error TS2701: Th
     ({a, ...rest.b + rest.b} = o);
             ~~~~~~~~~~~~~~~
 !!! error TS2701: The target of an object rest assignment must be a variable or a property access.
+
+    var noContextualType = ({ aNumber = 12, ...notEmptyObject }) => aNumber + notEmptyObject.anythingGoes;
+                                                                                             ~~~~~~~~~~~~
+!!! error TS2339: Property 'anythingGoes' does not exist on type '{ [x: string]: any; }'.
 

tests/baselines/reference/objectRestNegative.js

@@ -16,6 +16,8 @@ function generic<T extends { x, y }>(t: T) {
 
 let rest: { b: string }
 ({a, ...rest.b + rest.b} = o);
+
+var noContextualType = ({ aNumber = 12, ...notEmptyObject }) => aNumber + notEmptyObject.anythingGoes;
 
 
 //// [objectRestNegative.js]
@@ -42,3 +44,7 @@ function generic(t) {
 }
 var rest;
 (a = o.a, o, rest.b + rest.b = __rest(o, ["a"]));
+var noContextualType = function (_a) {
+    var _b = _a.aNumber, aNumber = _b === void 0 ? 12 : _b, notEmptyObject = __rest(_a, ["aNumber"]);
+    return aNumber + notEmptyObject.anythingGoes;
+};

tests/cases/conformance/types/rest/objectRest.ts

@@ -36,3 +36,5 @@ let computed = 'b';
 let computed2 = 'a';
 var { [computed]: stillNotGreat, [computed2]: soSo,  ...o } = o;
 ({ [computed]: stillNotGreat, [computed2]: soSo, ...o } = o);
+
+var noContextualType = ({ aNumber = 12, ...notEmptyObject }) => aNumber + notEmptyObject['anythingGoes'];

tests/cases/conformance/types/rest/objectRestNegative.ts

@@ -1,3 +1,4 @@
+// @noImplicitAny: true
 let o = { a: 1, b: 'no' };
 var { ...mustBeLast, a } = o;
 
@@ -15,3 +16,5 @@ function generic<T extends { x, y }>(t: T) {
 
 let rest: { b: string }
 ({a, ...rest.b + rest.b} = o);
+
+var noContextualType = ({ aNumber = 12, ...notEmptyObject }) => aNumber + notEmptyObject.anythingGoes;