Property assignments in Typescript (#26368)

* Allow special property assignments in TS

But only for functions and constant variable declarations initialised with
functions.

This specifically excludes class declarations and class expressions,
which differs from Javascript. That's because Typescript supports
`static` properties, which are equivalent to property assignments to a
class.

* Improve contextual typing predicate

Don't think it's right yet, but probably closer?

* More fixes.

The code is still fantastically ugly, but everything works the way it
should.

Also update baselines, even where it is ill-advised.

* Cleanup

* Remove extra whitespace

* Some kind of fix to isAnyDeclarationName

It's not done yet.

Specifically, in TS:
Special property assignments are supposed to be declaration sites (but not all
top-level assignments), and I think I
got them to be. (But not sure).

In JS:
Special property assignments are supposed to be declaration sites (but not all
top-level assignments), and I'm pretty sure ALL top-level assignments
have been declaration sites for some time. This is incorrect, and
probably means the predicate needs to be the same for both dialects.

* Add fourslash and improve isAnyDeclarationName

Now JS behaves the same as TS.

* Cleanup from PR comments

Author: sandersn

src/compiler/binder.ts

@@ -2480,6 +2480,11 @@ namespace ts {
 
         function bindSpecialPropertyAssignment(node: BinaryExpression) {
             const lhs = node.left as PropertyAccessEntityNameExpression;
+            // Class declarations in Typescript do not allow property declarations
+            const parentSymbol = lookupSymbolForPropertyAccess(lhs.expression);
+            if (!isInJavaScriptFile(node) && !isFunctionSymbol(parentSymbol)) {
+                return;
+            }
             // Fix up parent pointers since we're going to use these nodes before we bind into them
             node.left.parent = node;
             node.right.parent = node;

src/compiler/checker.ts

@@ -4821,48 +4821,45 @@ namespace ts {
         }
 
         /** If we don't have an explicit JSDoc type, get the type from the initializer. */
-        function getInitializerTypeFromSpecialDeclarations(symbol: Symbol, resolvedSymbol: Symbol | undefined, expression: Expression, special: SpecialPropertyAssignmentKind) {
-            if (isBinaryExpression(expression)) {
-                const type = resolvedSymbol ? getTypeOfSymbol(resolvedSymbol) : getWidenedLiteralType(checkExpressionCached(expression.right));
-                if (type.flags & TypeFlags.Object &&
-                    special === SpecialPropertyAssignmentKind.ModuleExports &&
-                    symbol.escapedName === InternalSymbolName.ExportEquals) {
-                    const exportedType = resolveStructuredTypeMembers(type as ObjectType);
-                    const members = createSymbolTable();
-                    copyEntries(exportedType.members, members);
-                    if (resolvedSymbol && !resolvedSymbol.exports) {
-                        resolvedSymbol.exports = createSymbolTable();
-                    }
-                    (resolvedSymbol || symbol).exports!.forEach((s, name) => {
-                        if (members.has(name)) {
-                            const exportedMember = exportedType.members.get(name)!;
-                            const union = createSymbol(s.flags | exportedMember.flags, name);
-                            union.type = getUnionType([getTypeOfSymbol(s), getTypeOfSymbol(exportedMember)]);
-                            members.set(name, union);
-                        }
-                        else {
-                            members.set(name, s);
-                        }
-                    });
-                    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;
+        function getInitializerTypeFromSpecialDeclarations(symbol: Symbol, resolvedSymbol: Symbol | undefined, expression: BinaryExpression, special: SpecialPropertyAssignmentKind) {
+            const type = resolvedSymbol ? getTypeOfSymbol(resolvedSymbol) : getWidenedLiteralType(checkExpressionCached(expression.right));
+            if (type.flags & TypeFlags.Object &&
+                special === SpecialPropertyAssignmentKind.ModuleExports &&
+                symbol.escapedName === InternalSymbolName.ExportEquals) {
+                const exportedType = resolveStructuredTypeMembers(type as ObjectType);
+                const members = createSymbolTable();
+                copyEntries(exportedType.members, members);
+                if (resolvedSymbol && !resolvedSymbol.exports) {
+                    resolvedSymbol.exports = createSymbolTable();
                 }
-                if (isEmptyArrayLiteralType(type)) {
-                    if (noImplicitAny) {
-                        reportImplicitAnyError(expression, anyArrayType);
+                (resolvedSymbol || symbol).exports!.forEach((s, name) => {
+                    if (members.has(name)) {
+                        const exportedMember = exportedType.members.get(name)!;
+                        const union = createSymbol(s.flags | exportedMember.flags, name);
+                        union.type = getUnionType([getTypeOfSymbol(s), getTypeOfSymbol(exportedMember)]);
+                        members.set(name, union);
                     }
-                    return anyArrayType;
+                    else {
+                        members.set(name, s);
+                    }
+                });
+                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) {
+                    reportImplicitAnyError(expression, anyArrayType);
                 }
-                return type;
+                return anyArrayType;
             }
-            return neverType;
+            return type;
         }
 
         function isDeclarationInConstructor(expression: Expression) {
@@ -5085,7 +5082,9 @@ namespace ts {
                 if (symbol.flags & (SymbolFlags.Function | SymbolFlags.Method | SymbolFlags.Class | SymbolFlags.Enum | SymbolFlags.ValueModule)) {
                     return getTypeOfFuncClassEnumModule(symbol);
                 }
-                type = tryGetTypeFromEffectiveTypeNode(declaration) || anyType;
+                type = isBinaryExpression(declaration.parent) ?
+                    getWidenedTypeFromJSPropertyAssignments(symbol) :
+                    tryGetTypeFromEffectiveTypeNode(declaration) || anyType;
             }
             else if (isPropertyAssignment(declaration)) {
                 type = tryGetTypeFromEffectiveTypeNode(declaration) || checkPropertyAssignment(declaration);
@@ -16025,7 +16024,24 @@ namespace ts {
                 case SpecialPropertyAssignmentKind.PrototypeProperty:
                     // If `binaryExpression.left` was assigned a symbol, then this is a new declaration; otherwise it is an assignment to an existing declaration.
                     // See `bindStaticPropertyAssignment` in `binder.ts`.
-                    return !binaryExpression.left.symbol || binaryExpression.left.symbol.valueDeclaration && !!getJSDocTypeTag(binaryExpression.left.symbol.valueDeclaration);
+                    if (!binaryExpression.left.symbol) {
+                        return true;
+                    }
+                    else {
+                        const decl = binaryExpression.left.symbol.valueDeclaration;
+                        if (!decl) {
+                            return false;
+                        }
+                        if (isInJavaScriptFile(decl)) {
+                            return !!getJSDocTypeTag(decl);
+                        }
+                        else if (isIdentifier((binaryExpression.left as PropertyAccessExpression).expression)) {
+                            const id = (binaryExpression.left as PropertyAccessExpression).expression as Identifier;
+                            const parentSymbol = resolveName(id, id.escapedText, SymbolFlags.Value, undefined, id.escapedText, /*isUse*/ true);
+                            return !isFunctionSymbol(parentSymbol);
+                        }
+                        return true;
+                    }
                 case SpecialPropertyAssignmentKind.ThisProperty:
                 case SpecialPropertyAssignmentKind.ModuleExports:
                     return !binaryExpression.symbol || binaryExpression.symbol.valueDeclaration && !!getJSDocTypeTag(binaryExpression.symbol.valueDeclaration);

src/compiler/utilities.ts

@@ -1725,12 +1725,15 @@ namespace ts {
     }
 
     export function getDeclarationOfJSInitializer(node: Node): Node | undefined {
-        if (!isInJavaScriptFile(node) || !node.parent) {
+        if (!node.parent) {
             return undefined;
         }
         let name: Expression | BindingName | undefined;
         let decl: Node | undefined;
         if (isVariableDeclaration(node.parent) && node.parent.initializer === node) {
+            if (!isInJavaScriptFile(node) && !isVarConst(node.parent)) {
+                return undefined;
+            }
             name = node.parent.name;
             decl = node.parent;
         }
@@ -1892,8 +1895,12 @@ namespace ts {
     /// Given a BinaryExpression, returns SpecialPropertyAssignmentKind for the various kinds of property
     /// assignments we treat as special in the binder
     export function getSpecialPropertyAssignmentKind(expr: BinaryExpression): SpecialPropertyAssignmentKind {
-        if (!isInJavaScriptFile(expr) ||
-            expr.operatorToken.kind !== SyntaxKind.EqualsToken ||
+        const special = getSpecialPropertyAssignmentKindWorker(expr);
+        return special === SpecialPropertyAssignmentKind.Property || isInJavaScriptFile(expr) ? special : SpecialPropertyAssignmentKind.None;
+    }
+
+    function getSpecialPropertyAssignmentKindWorker(expr: BinaryExpression): SpecialPropertyAssignmentKind {
+        if (expr.operatorToken.kind !== SyntaxKind.EqualsToken ||
             !isPropertyAccessExpression(expr.left)) {
             return SpecialPropertyAssignmentKind.None;
         }
@@ -1954,6 +1961,14 @@ namespace ts {
             !!getJSDocTypeTag(expr.parent);
     }
 
+    export function isFunctionSymbol(symbol: Symbol | undefined) {
+        if (!symbol || !symbol.valueDeclaration) {
+            return false;
+        }
+        const decl = symbol.valueDeclaration;
+        return decl.kind === SyntaxKind.FunctionDeclaration || isVariableDeclaration(decl) && decl.initializer && isFunctionLike(decl.initializer);
+    }
+
     export function importFromModuleSpecifier(node: StringLiteralLike): AnyValidImportOrReExport {
         return tryGetImportFromModuleSpecifier(node) || Debug.fail(Debug.showSyntaxKind(node.parent));
     }
@@ -2354,7 +2369,10 @@ namespace ts {
                 }
                 else {
                     const binExp = name.parent.parent;
-                    return isBinaryExpression(binExp) && getSpecialPropertyAssignmentKind(binExp) !== SpecialPropertyAssignmentKind.None && getNameOfDeclaration(binExp) === name;
+                    return isBinaryExpression(binExp) &&
+                        getSpecialPropertyAssignmentKind(binExp) !== SpecialPropertyAssignmentKind.None &&
+                        (binExp.left.symbol || binExp.symbol) &&
+                        getNameOfDeclaration(binExp) === name;
                 }
             }
             default:

tests/baselines/reference/fixSignatureCaching.errors.txt

@@ -24,7 +24,6 @@ tests/cases/conformance/fixSignatureCaching.ts(474,38): error TS2339: Property '
 tests/cases/conformance/fixSignatureCaching.ts(481,22): error TS2339: Property 'findMatch' does not exist on type '{}'.
 tests/cases/conformance/fixSignatureCaching.ts(481,37): error TS2339: Property 'mobileDetectRules' does not exist on type '{}'.
 tests/cases/conformance/fixSignatureCaching.ts(489,18): error TS2339: Property 'isMobileFallback' does not exist on type '{}'.
-tests/cases/conformance/fixSignatureCaching.ts(490,39): error TS2339: Property 'isPhoneSized' does not exist on type '(userAgent: any, maxPhoneWidth: any) => void'.
 tests/cases/conformance/fixSignatureCaching.ts(492,37): error TS2339: Property 'FALLBACK_MOBILE' does not exist on type '{}'.
 tests/cases/conformance/fixSignatureCaching.ts(495,51): error TS2339: Property 'FALLBACK_PHONE' does not exist on type '{}'.
 tests/cases/conformance/fixSignatureCaching.ts(498,52): error TS2339: Property 'FALLBACK_TABLET' does not exist on type '{}'.
@@ -49,13 +48,8 @@ tests/cases/conformance/fixSignatureCaching.ts(872,25): error TS2339: Property '
 tests/cases/conformance/fixSignatureCaching.ts(893,25): error TS2339: Property 'getVersionStr' does not exist on type '{}'.
 tests/cases/conformance/fixSignatureCaching.ts(915,36): error TS2339: Property 'findMatches' does not exist on type '{}'.
 tests/cases/conformance/fixSignatureCaching.ts(915,53): error TS2339: Property 'mobileDetectRules' does not exist on type '{}'.
-tests/cases/conformance/fixSignatureCaching.ts(944,33): error TS2339: Property 'isPhoneSized' does not exist on type '(userAgent: any, maxPhoneWidth: any) => void'.
 tests/cases/conformance/fixSignatureCaching.ts(955,42): error TS2339: Property 'mobileGrade' does not exist on type '{}'.
-tests/cases/conformance/fixSignatureCaching.ts(963,22): error TS2339: Property 'isPhoneSized' does not exist on type '(userAgent: any, maxPhoneWidth: any) => void'.
 tests/cases/conformance/fixSignatureCaching.ts(964,57): error TS2339: Property 'getDeviceSmallerSide' does not exist on type '{}'.
-tests/cases/conformance/fixSignatureCaching.ts(967,22): error TS2339: Property 'isPhoneSized' does not exist on type '(userAgent: any, maxPhoneWidth: any) => void'.
-tests/cases/conformance/fixSignatureCaching.ts(971,18): error TS2339: Property '_impl' does not exist on type '(userAgent: any, maxPhoneWidth: any) => void'.
-tests/cases/conformance/fixSignatureCaching.ts(973,18): error TS2339: Property 'version' does not exist on type '(userAgent: any, maxPhoneWidth: any) => void'.
 tests/cases/conformance/fixSignatureCaching.ts(978,16): error TS2304: Cannot find name 'module'.
 tests/cases/conformance/fixSignatureCaching.ts(978,42): error TS2304: Cannot find name 'module'.
 tests/cases/conformance/fixSignatureCaching.ts(979,37): error TS2304: Cannot find name 'module'.
@@ -65,7 +59,7 @@ tests/cases/conformance/fixSignatureCaching.ts(981,16): error TS2304: Cannot fin
 tests/cases/conformance/fixSignatureCaching.ts(983,44): error TS2339: Property 'MobileDetect' does not exist on type 'Window'.
 
 
-==== tests/cases/conformance/fixSignatureCaching.ts (65 errors) ====
+==== tests/cases/conformance/fixSignatureCaching.ts (59 errors) ====
     // Repro from #10697
 
     (function (define, undefined) {
@@ -608,8 +602,6 @@ tests/cases/conformance/fixSignatureCaching.ts(983,44): error TS2339: Property '
                      ~~~~~~~~~~~~~~~~
 !!! error TS2339: Property 'isMobileFallback' does not exist on type '{}'.
                 phoneSized = MobileDetect.isPhoneSized(maxPhoneWidth);
-                                          ~~~~~~~~~~~~
-!!! error TS2339: Property 'isPhoneSized' does not exist on type '(userAgent: any, maxPhoneWidth: any) => void'.
                 if (phoneSized === undefined) {
                     cache.mobile = impl.FALLBACK_MOBILE;
                                         ~~~~~~~~~~~~~~~
@@ -1112,8 +1104,6 @@ tests/cases/conformance/fixSignatureCaching.ts(983,44): error TS2339: Property '
              */
             isPhoneSized: function (maxPhoneWidth) {
                 return MobileDetect.isPhoneSized(maxPhoneWidth || this.maxPhoneWidth);
-                                    ~~~~~~~~~~~~
-!!! error TS2339: Property 'isPhoneSized' does not exist on type '(userAgent: any, maxPhoneWidth: any) => void'.
             },
 
             /**
@@ -1135,26 +1125,18 @@ tests/cases/conformance/fixSignatureCaching.ts(983,44): error TS2339: Property '
         // environment-dependent
         if (typeof window !== 'undefined' && window.screen) {
             MobileDetect.isPhoneSized = function (maxPhoneWidth) {
-                         ~~~~~~~~~~~~
-!!! error TS2339: Property 'isPhoneSized' does not exist on type '(userAgent: any, maxPhoneWidth: any) => void'.
                 return maxPhoneWidth < 0 ? undefined : impl.getDeviceSmallerSide() <= maxPhoneWidth;
                                                             ~~~~~~~~~~~~~~~~~~~~
 !!! error TS2339: Property 'getDeviceSmallerSide' does not exist on type '{}'.
             };
         } else {
             MobileDetect.isPhoneSized = function () {};
-                         ~~~~~~~~~~~~
-!!! error TS2339: Property 'isPhoneSized' does not exist on type '(userAgent: any, maxPhoneWidth: any) => void'.
         }
 
         // should not be replaced by a completely new object - just overwrite existing methods
         MobileDetect._impl = impl;
-                     ~~~~~
-!!! error TS2339: Property '_impl' does not exist on type '(userAgent: any, maxPhoneWidth: any) => void'.
 
         MobileDetect.version = '1.3.3 2016-07-31';
-                     ~~~~~~~
-!!! error TS2339: Property 'version' does not exist on type '(userAgent: any, maxPhoneWidth: any) => void'.
 
         return MobileDetect;
     }); // end of call of define()
@@ -1183,4 +1165,5 @@ tests/cases/conformance/fixSignatureCaching.ts(983,44): error TS2339: Property '
             // please file a bug if you get this error!
             throw new Error('unknown environment');
         }
-    })());
+    })());
+    

tests/baselines/reference/fixSignatureCaching.js

@@ -986,7 +986,8 @@ define(function () {
         // please file a bug if you get this error!
         throw new Error('unknown environment');
     }
-})());
+})());
+
 
 //// [fixSignatureCaching.js]
 // Repro from #10697