Flag JS Literals and ignore assignments/accesses to invalid props, instead of adding an index

src/compiler/checker.ts

@@ -425,7 +425,6 @@ namespace ts {
         const resolvingSignaturesArray = [resolvingSignature];
 
         const enumNumberIndexInfo = createIndexInfo(stringType, /*isReadonly*/ true);
-        const jsObjectLiteralIndexInfo = createIndexInfo(anyType, /*isReadonly*/ false);
 
         const globals = createSymbolTable();
         let amalgamatedDuplicates: Map<{ firstFile: SourceFile, secondFile: SourceFile, firstFileInstances: Map<{ instances: Node[], blockScoped: boolean }>, secondFileInstances: Map<{ instances: Node[], blockScoped: boolean }> }> | undefined;
@@ -4807,13 +4806,15 @@ namespace ts {
                             members.set(name, s);
                         }
                     });
-                    return createAnonymousType(
+                    const result = createAnonymousType(
                         exportedType.symbol,
                         members,
                         exportedType.callSignatures,
                         exportedType.constructSignatures,
                         exportedType.stringIndexInfo,
                         exportedType.numberIndexInfo);
+                    result.objectFlags |= (getObjectFlags(type) & ObjectFlags.JSLiteral); // Propagate JSLiteral flag
+                    return result;
                 }
                 if (isEmptyArrayLiteralType(type)) {
                     if (noImplicitAny) {
@@ -5121,7 +5122,9 @@ namespace ts {
                 if (s && hasEntries(s.exports)) {
                     mergeSymbolTable(exports, s.exports);
                 }
-                return createAnonymousType(symbol, exports, emptyArray, emptyArray, jsObjectLiteralIndexInfo, undefined);
+                const type = createAnonymousType(symbol, exports, emptyArray, emptyArray, undefined, undefined);
+                type.objectFlags |= ObjectFlags.JSLiteral;
+                return type;
             }
         }
 
@@ -9072,6 +9075,34 @@ namespace ts {
             return type;
         }
 
+        /**
+         * Returns if a type is or consists of a JSLiteral object type
+         * In addition to objects which are directly literals,
+         * * unions where every element is a jsliteral
+         * * intersections where at least one element is a jsliteral
+         * * and instantiable types constrained to a jsliteral
+         * Should all count as literals and not print errors on access or assignment of possibly existing properties.
+         * This mirrors the behavior of the index signature propagation, to which this behaves similarly (but doesn't affect assignability or inference).
+         */
+        function isJSLiteralType(type: Type): boolean {
+            if (noImplicitAny) {
+                return false; // Flag is meaningless under `noImplicitAny` mode
+            }
+            if (getObjectFlags(type) & ObjectFlags.JSLiteral) {
+                return true;
+            }
+            if (type.flags & TypeFlags.Union) {
+                return every((type as UnionType).types, isJSLiteralType);
+            }
+            if (type.flags & TypeFlags.Intersection) {
+                return some((type as IntersectionType).types, isJSLiteralType);
+            }
+            if (type.flags & TypeFlags.Instantiable) {
+                return isJSLiteralType(getResolvedBaseConstraint(type));
+            }
+            return false;
+        }
+
         function getPropertyTypeForIndexType(objectType: Type, indexType: Type, accessNode: ElementAccessExpression | IndexedAccessTypeNode | undefined, cacheSymbol: boolean) {
             const accessExpression = accessNode && accessNode.kind === SyntaxKind.ElementAccessExpression ? accessNode : undefined;
             const propName = isTypeUsableAsLateBoundName(indexType) ? getLateBoundNameFromType(indexType) :
@@ -9120,6 +9151,9 @@ namespace ts {
                 if (indexType.flags & TypeFlags.Never) {
                     return neverType;
                 }
+                if (isJSLiteralType(objectType)) {
+                    return anyType;
+                }
                 if (accessExpression && !isConstEnumObjectType(objectType)) {
                     if (noImplicitAny && !compilerOptions.suppressImplicitAnyIndexErrors) {
                         if (getIndexTypeOfType(objectType, IndexKind.Number)) {
@@ -9140,6 +9174,9 @@ namespace ts {
                     return anyType;
                 }
             }
+            if (isJSLiteralType(objectType)) {
+                return anyType;
+            }
             if (accessNode) {
                 const indexNode = accessNode.kind === SyntaxKind.ElementAccessExpression ? accessNode.argumentExpression : accessNode.indexType;
                 if (indexType.flags & (TypeFlags.StringLiteral | TypeFlags.NumberLiteral)) {
@@ -11215,6 +11252,9 @@ namespace ts {
             }
 
             function hasExcessProperties(source: FreshObjectLiteralType, target: Type, discriminant: Type | undefined, reportErrors: boolean): boolean {
+                if (!noImplicitAny && getObjectFlags(target) & ObjectFlags.JSLiteral) {
+                    return false; // Disable excess property checks on JS literals to simulate having an implicit "index signature" - but only outside of noImplicitAny
+                }
                 if (maybeTypeOfKind(target, TypeFlags.Object) && !(getObjectFlags(target) & ObjectFlags.ObjectLiteralPatternWithComputedProperties)) {
                     const isComparingJsxAttributes = !!(getObjectFlags(source) & ObjectFlags.JsxAttributes);
                     if ((relation === assignableRelation || relation === definitelyAssignableRelation || relation === comparableRelation) &&
@@ -12703,7 +12743,7 @@ namespace ts {
                 resolved.stringIndexInfo,
                 resolved.numberIndexInfo);
             regularNew.flags = resolved.flags & ~TypeFlags.FreshLiteral;
-            regularNew.objectFlags |= ObjectFlags.ObjectLiteral;
+            regularNew.objectFlags |= ObjectFlags.ObjectLiteral | (getObjectFlags(resolved) & ObjectFlags.JSLiteral);
             (<FreshObjectLiteralType>type).regularType = regularNew;
             return regularNew;
         }
@@ -12782,9 +12822,11 @@ namespace ts {
             }
             const stringIndexInfo = getIndexInfoOfType(type, IndexKind.String);
             const numberIndexInfo = getIndexInfoOfType(type, IndexKind.Number);
-            return createAnonymousType(type.symbol, members, emptyArray, emptyArray,
+            const result = createAnonymousType(type.symbol, members, emptyArray, emptyArray,
                 stringIndexInfo && createIndexInfo(getWidenedType(stringIndexInfo.type), stringIndexInfo.isReadonly),
                 numberIndexInfo && createIndexInfo(getWidenedType(numberIndexInfo.type), numberIndexInfo.isReadonly));
+            result.objectFlags |= (getObjectFlags(type) & ObjectFlags.JSLiteral); // Retain js literal flag through widening
+            return result;
         }
 
         function getWidenedType(type: Type) {
@@ -16789,12 +16831,15 @@ namespace ts {
             return createObjectLiteralType();
 
             function createObjectLiteralType() {
-                const stringIndexInfo = isJSObjectLiteral ? jsObjectLiteralIndexInfo : hasComputedStringProperty ? getObjectLiteralIndexInfo(node.properties, offset, propertiesArray, IndexKind.String) : undefined;
+                const stringIndexInfo = hasComputedStringProperty ? getObjectLiteralIndexInfo(node.properties, offset, propertiesArray, IndexKind.String) : undefined;
                 const numberIndexInfo = hasComputedNumberProperty && !isJSObjectLiteral ? getObjectLiteralIndexInfo(node.properties, offset, propertiesArray, IndexKind.Number) : undefined;
                 const result = createAnonymousType(node.symbol, propertiesTable, emptyArray, emptyArray, stringIndexInfo, numberIndexInfo);
                 const freshObjectLiteralFlag = compilerOptions.suppressExcessPropertyErrors ? 0 : TypeFlags.FreshLiteral;
                 result.flags |= TypeFlags.ContainsObjectLiteral | freshObjectLiteralFlag | (typeFlags & TypeFlags.PropagatingFlags);
                 result.objectFlags |= ObjectFlags.ObjectLiteral;
+                if (isJSObjectLiteral) {
+                    result.objectFlags |= ObjectFlags.JSLiteral;
+                }
                 if (patternWithComputedProperties) {
                     result.objectFlags |= ObjectFlags.ObjectLiteralPatternWithComputedProperties;
                 }
@@ -17870,6 +17915,9 @@ namespace ts {
             if (!prop) {
                 const indexInfo = getIndexInfoOfType(apparentType, IndexKind.String);
                 if (!(indexInfo && indexInfo.type)) {
+                    if (isJSLiteralType(leftType)) {
+                        return anyType;
+                    }
                     if (right.escapedText && !checkAndReportErrorForExtendingInterface(node)) {
                         reportNonexistentProperty(right, leftType.flags & TypeFlags.TypeParameter && (leftType as TypeParameter).isThisType ? apparentType : leftType);
                     }
@@ -20007,7 +20055,8 @@ namespace ts {
                 if (decl) {
                     const jsSymbol = getSymbolOfNode(decl);
                     if (jsSymbol && hasEntries(jsSymbol.exports)) {
-                        jsAssignmentType = createAnonymousType(jsSymbol, jsSymbol.exports, emptyArray, emptyArray, jsObjectLiteralIndexInfo, undefined);
+                        jsAssignmentType = createAnonymousType(jsSymbol, jsSymbol.exports, emptyArray, emptyArray, undefined, undefined);
+                        (jsAssignmentType as ObjectType).objectFlags |= ObjectFlags.JSLiteral;
                     }
                 }
             }

src/compiler/types.ts

@@ -3817,6 +3817,7 @@ namespace ts {
         ReverseMapped    = 1 << 11, // Object contains a property from a reverse-mapped type
         JsxAttributes    = 1 << 12, // Jsx attributes type
         MarkerType       = 1 << 13, // Marker type used for variance probing
+        JSLiteral        = 1 << 14, // Object type declared in JS - disables errors on read/write of nonexisting members
         ClassOrInterface = Class | Interface
     }
 

tests/baselines/reference/api/tsserverlibrary.d.ts

@@ -2231,6 +2231,7 @@ declare namespace ts {
         ReverseMapped = 2048,
         JsxAttributes = 4096,
         MarkerType = 8192,
+        JSLiteral = 16384,
         ClassOrInterface = 3
     }
     interface ObjectType extends Type {

tests/baselines/reference/api/typescript.d.ts

@@ -2231,6 +2231,7 @@ declare namespace ts {
         ReverseMapped = 2048,
         JsxAttributes = 4096,
         MarkerType = 8192,
+        JSLiteral = 16384,
         ClassOrInterface = 3
     }
     interface ObjectType extends Type {

tests/baselines/reference/chainedPrototypeAssignment.types

@@ -7,30 +7,30 @@ var mod = require('./mod');
 >'./mod' : "./mod"
 
 var a = new mod.A()
->a : A & { [x: string]: any; m(n: number): number; }
->new mod.A() : A & { [x: string]: any; m(n: number): number; }
+>a : A & { m(n: number): number; }
+>new mod.A() : A & { m(n: number): number; }
 >mod.A : typeof A
 >mod : typeof import("tests/cases/conformance/salsa/mod")
 >A : typeof A
 
 var b = new mod.B()
->b : B & { [x: string]: any; m(n: number): number; }
->new mod.B() : B & { [x: string]: any; m(n: number): number; }
+>b : B & { m(n: number): number; }
+>new mod.B() : B & { m(n: number): number; }
 >mod.B : typeof B
 >mod : typeof import("tests/cases/conformance/salsa/mod")
 >B : typeof B
 
 a.m('nope')
 >a.m('nope') : number
 >a.m : (n: number) => number
->a : A & { [x: string]: any; m(n: number): number; }
+>a : A & { m(n: number): number; }
 >m : (n: number) => number
 >'nope' : "nope"
 
 b.m('not really')
 >b.m('not really') : number
 >b.m : (n: number) => number
->b : B & { [x: string]: any; m(n: number): number; }
+>b : B & { m(n: number): number; }
 >m : (n: number) => number
 >'not really' : "not really"
 
@@ -81,15 +81,15 @@ exports.B = B
 >B : typeof B
 
 A.prototype = B.prototype = {
->A.prototype = B.prototype = {    /** @param {number} n */    m(n) {        return n + 1    }} : { [x: string]: any; m(n: number): number; }
->A.prototype : { [x: string]: any; m(n: number): number; }
+>A.prototype = B.prototype = {    /** @param {number} n */    m(n) {        return n + 1    }} : { m(n: number): number; }
+>A.prototype : { m(n: number): number; }
 >A : typeof A
->prototype : { [x: string]: any; m(n: number): number; }
->B.prototype = {    /** @param {number} n */    m(n) {        return n + 1    }} : { [x: string]: any; m(n: number): number; }
->B.prototype : { [x: string]: any; m(n: number): number; }
+>prototype : { m(n: number): number; }
+>B.prototype = {    /** @param {number} n */    m(n) {        return n + 1    }} : { m(n: number): number; }
+>B.prototype : { m(n: number): number; }
 >B : typeof B
->prototype : { [x: string]: any; m(n: number): number; }
->{    /** @param {number} n */    m(n) {        return n + 1    }} : { [x: string]: any; m(n: number): number; }
+>prototype : { m(n: number): number; }
+>{    /** @param {number} n */    m(n) {        return n + 1    }} : { m(n: number): number; }
 
     /** @param {number} n */
     m(n) {

tests/baselines/reference/checkDestructuringShorthandAssigment.types

@@ -1,17 +1,17 @@
 === tests/cases/compiler/bug25434.js ===
 // should not crash while checking
 function Test({ b = '' } = {}) {}
->Test : ({ b }?: { [x: string]: any; }) => void
+>Test : ({ b }?: {}) => void
 >b : string
 >'' : ""
 >{} : { b?: string; }
 
 Test(({ b = '5' } = {}));
 >Test(({ b = '5' } = {})) : void
->Test : ({ b }?: { [x: string]: any; }) => void
+>Test : ({ b }?: {}) => void
 >({ b = '5' } = {}) : { b?: any; }
 >{ b = '5' } = {} : { b?: any; }
->{ b = '5' } : { [x: string]: any; b?: any; }
+>{ b = '5' } : { b?: any; }
 >b : any
 >'5' : "5"
 >{} : { b?: any; }

tests/baselines/reference/checkJsObjectLiteralHasCheckedKeyof.errors.txt

@@ -0,0 +1,18 @@
+tests/cases/compiler/file.js(11,1): error TS2322: Type '"z"' is not assignable to type '"x" | "y"'.
+
+
+==== tests/cases/compiler/file.js (1 errors) ====
+    // @ts-check
+    const obj = {
+        x: 1,
+        y: 2
+    };
+
+    /**
+     * @type {keyof typeof obj}
+     */
+    let selected = "x";
+    selected = "z"; // should fail
+    ~~~~~~~~
+!!! error TS2322: Type '"z"' is not assignable to type '"x" | "y"'.
+

tests/baselines/reference/checkJsObjectLiteralHasCheckedKeyof.js

@@ -0,0 +1,25 @@
+//// [file.js]
+// @ts-check
+const obj = {
+    x: 1,
+    y: 2
+};
+
+/**
+ * @type {keyof typeof obj}
+ */
+let selected = "x";
+selected = "z"; // should fail
+
+
+//// [file.js]
+// @ts-check
+var obj = {
+    x: 1,
+    y: 2
+};
+/**
+ * @type {keyof typeof obj}
+ */
+var selected = "x";
+selected = "z"; // should fail

tests/baselines/reference/checkJsObjectLiteralHasCheckedKeyof.symbols

@@ -0,0 +1,22 @@
+=== tests/cases/compiler/file.js ===
+// @ts-check
+const obj = {
+>obj : Symbol(obj, Decl(file.js, 1, 5))
+
+    x: 1,
+>x : Symbol(x, Decl(file.js, 1, 13))
+
+    y: 2
+>y : Symbol(y, Decl(file.js, 2, 9))
+
+};
+
+/**
+ * @type {keyof typeof obj}
+ */
+let selected = "x";
+>selected : Symbol(selected, Decl(file.js, 9, 3))
+
+selected = "z"; // should fail
+>selected : Symbol(selected, Decl(file.js, 9, 3))
+

tests/baselines/reference/checkJsObjectLiteralHasCheckedKeyof.types

@@ -0,0 +1,28 @@
+=== tests/cases/compiler/file.js ===
+// @ts-check
+const obj = {
+>obj : { x: number; y: number; }
+>{    x: 1,    y: 2} : { x: number; y: number; }
+
+    x: 1,
+>x : number
+>1 : 1
+
+    y: 2
+>y : number
+>2 : 2
+
+};
+
+/**
+ * @type {keyof typeof obj}
+ */
+let selected = "x";
+>selected : "x" | "y"
+>"x" : "x"
+
+selected = "z"; // should fail
+>selected = "z" : "z"
+>selected : "x" | "y"
+>"z" : "z"
+