Declaration emit includes function properties (#26499)

* Declaration emit includes function properties

It does this by printing the type as an object literal type:

```ts
function f() { }
f.p = 1
```

Appears in a d.ts as

```ts
declare var f: {
  (): void;
  p: number;
}
```

It would also be possible to represent it as a namespace merge. I'm not
sure which is better.

```ts
declare function f(): void;
declare namespace f {
  export var p: number;
}
```

In order to avoid a private-name-used error (though I think it was
actually *unused*), I also had to change the nodeBuilder code to match.
This is arguably harder to read. So it's possible that I should instead
keep the nodeBuilder version as `typeof f` and make an exception for
private name use.

* Emit namespace merge instead of object type

This makes the change smaller, overall.

* Fix isJSContainerFunctionDeclaration+namespace merges

Also improve emit style to match other namespace emit.

* Add isPrivate + test case from PR comments

Author: sandersn

src/compiler/checker.ts

@@ -27767,6 +27767,27 @@ namespace ts {
                 hasModifier(parameter, ModifierFlags.ParameterPropertyModifier);
         }
 
+        function isJSContainerFunctionDeclaration(node: Declaration): boolean {
+            const declaration = getParseTreeNode(node, isFunctionDeclaration);
+            if (!declaration) {
+                return false;
+            }
+            const symbol = getSymbolOfNode(declaration);
+            if (!symbol || !(symbol.flags & SymbolFlags.Function)) {
+                return false;
+            }
+            return !!forEachEntry(getExportsOfSymbol(symbol), p => isPropertyAccessExpression(p.valueDeclaration));
+        }
+
+        function getPropertiesOfContainerFunction(node: Declaration): Symbol[] {
+            const declaration = getParseTreeNode(node, isFunctionDeclaration);
+            if (!declaration) {
+                return emptyArray;
+            }
+            const symbol = getSymbolOfNode(declaration);
+            return symbol && getPropertiesOfType(getTypeOfSymbol(symbol)) || emptyArray;
+        }
+
         function getNodeCheckFlags(node: Node): NodeCheckFlags {
             return getNodeLinks(node).flags || 0;
         }
@@ -27874,7 +27895,7 @@ namespace ts {
             }
         }
 
-        function createTypeOfDeclaration(declarationIn: AccessorDeclaration | VariableLikeDeclaration, enclosingDeclaration: Node, flags: NodeBuilderFlags, tracker: SymbolTracker, addUndefined?: boolean) {
+        function createTypeOfDeclaration(declarationIn: AccessorDeclaration | VariableLikeDeclaration | PropertyAccessExpression, enclosingDeclaration: Node, flags: NodeBuilderFlags, tracker: SymbolTracker, addUndefined?: boolean) {
             const declaration = getParseTreeNode(declarationIn, isVariableLikeOrAccessor);
             if (!declaration) {
                 return createToken(SyntaxKind.AnyKeyword) as KeywordTypeNode;
@@ -28007,6 +28028,8 @@ namespace ts {
                 isImplementationOfOverload,
                 isRequiredInitializedParameter,
                 isOptionalUninitializedParameterProperty,
+                isJSContainerFunctionDeclaration,
+                getPropertiesOfContainerFunction,
                 createTypeOfDeclaration,
                 createReturnTypeOfSignatureDeclaration,
                 createTypeOfExpression,

src/compiler/transformers/declarations.ts

@@ -971,7 +971,7 @@ namespace ts {
                 }
                 case SyntaxKind.FunctionDeclaration: {
                     // Generators lose their generator-ness, excepting their return type
-                    return cleanup(updateFunctionDeclaration(
+                    const clean = cleanup(updateFunctionDeclaration(
                         input,
                         /*decorators*/ undefined,
                         ensureModifiers(input, isPrivate),
@@ -982,6 +982,21 @@ namespace ts {
                         ensureType(input, input.type),
                         /*body*/ undefined
                     ));
+                    if (clean && resolver.isJSContainerFunctionDeclaration(input)) {
+                        const declarations = mapDefined(resolver.getPropertiesOfContainerFunction(input), p => {
+                            if (!isPropertyAccessExpression(p.valueDeclaration)) {
+                                return undefined;
+                            }
+                            const type = resolver.createTypeOfDeclaration(p.valueDeclaration, enclosingDeclaration, declarationEmitNodeBuilderFlags, symbolTracker);
+                            const varDecl = createVariableDeclaration(unescapeLeadingUnderscores(p.escapedName), type, /*initializer*/ undefined);
+                            return createVariableStatement(/*modifiers*/ undefined, createVariableDeclarationList([varDecl]));
+                        });
+                        const namespaceDecl = createModuleDeclaration(/*decorators*/ undefined, ensureModifiers(input, isPrivate), input.name!, createModuleBlock(declarations), NodeFlags.Namespace);
+                        return [clean, namespaceDecl];
+                    }
+                    else {
+                        return clean;
+                    }
                 }
                 case SyntaxKind.ModuleDeclaration: {
                     needsDeclare = false;

src/compiler/types.ts

@@ -3374,7 +3374,9 @@ namespace ts {
         isImplementationOfOverload(node: FunctionLike): boolean | undefined;
         isRequiredInitializedParameter(node: ParameterDeclaration): boolean;
         isOptionalUninitializedParameterProperty(node: ParameterDeclaration): boolean;
-        createTypeOfDeclaration(declaration: AccessorDeclaration | VariableLikeDeclaration, enclosingDeclaration: Node, flags: NodeBuilderFlags, tracker: SymbolTracker, addUndefined?: boolean): TypeNode | undefined;
+        isJSContainerFunctionDeclaration(node: FunctionDeclaration): boolean;
+        getPropertiesOfContainerFunction(node: Declaration): Symbol[];
+        createTypeOfDeclaration(declaration: AccessorDeclaration | VariableLikeDeclaration | PropertyAccessExpression, enclosingDeclaration: Node, flags: NodeBuilderFlags, tracker: SymbolTracker, addUndefined?: boolean): TypeNode | undefined;
         createReturnTypeOfSignatureDeclaration(signatureDeclaration: SignatureDeclaration, enclosingDeclaration: Node, flags: NodeBuilderFlags, tracker: SymbolTracker): TypeNode | undefined;
         createTypeOfExpression(expr: Expression, enclosingDeclaration: Node, flags: NodeBuilderFlags, tracker: SymbolTracker): TypeNode | undefined;
         createLiteralConstValue(node: VariableDeclaration | PropertyDeclaration | PropertySignature | ParameterDeclaration): Expression;

tests/baselines/reference/typeFromPropertyAssignment29.errors.txt

@@ -1,15 +1,15 @@
-tests/cases/conformance/salsa/typeFromPropertyAssignment29.ts(30,14): error TS2339: Property 'prop' does not exist on type '(n: number) => string'.
-tests/cases/conformance/salsa/typeFromPropertyAssignment29.ts(31,14): error TS2339: Property 'm' does not exist on type '(n: number) => string'.
-tests/cases/conformance/salsa/typeFromPropertyAssignment29.ts(34,22): error TS2339: Property 'prop' does not exist on type '(n: number) => string'.
-tests/cases/conformance/salsa/typeFromPropertyAssignment29.ts(34,42): error TS2339: Property 'm' does not exist on type '(n: number) => string'.
-tests/cases/conformance/salsa/typeFromPropertyAssignment29.ts(40,14): error TS2339: Property 'prop' does not exist on type 'typeof ExpandoClass'.
-tests/cases/conformance/salsa/typeFromPropertyAssignment29.ts(41,14): error TS2339: Property 'm' does not exist on type 'typeof ExpandoClass'.
-tests/cases/conformance/salsa/typeFromPropertyAssignment29.ts(44,22): error TS2339: Property 'prop' does not exist on type 'typeof ExpandoClass'.
-tests/cases/conformance/salsa/typeFromPropertyAssignment29.ts(44,42): error TS2339: Property 'm' does not exist on type 'typeof ExpandoClass'.
-tests/cases/conformance/salsa/typeFromPropertyAssignment29.ts(50,14): error TS2339: Property 'prop' does not exist on type 'typeof ExpandoExpr3'.
-tests/cases/conformance/salsa/typeFromPropertyAssignment29.ts(51,14): error TS2339: Property 'm' does not exist on type 'typeof ExpandoExpr3'.
-tests/cases/conformance/salsa/typeFromPropertyAssignment29.ts(54,22): error TS2339: Property 'prop' does not exist on type 'typeof ExpandoExpr3'.
-tests/cases/conformance/salsa/typeFromPropertyAssignment29.ts(54,42): error TS2339: Property 'm' does not exist on type 'typeof ExpandoExpr3'.
+tests/cases/conformance/salsa/typeFromPropertyAssignment29.ts(60,14): error TS2339: Property 'prop' does not exist on type '(n: number) => string'.
+tests/cases/conformance/salsa/typeFromPropertyAssignment29.ts(61,14): error TS2339: Property 'm' does not exist on type '(n: number) => string'.
+tests/cases/conformance/salsa/typeFromPropertyAssignment29.ts(64,22): error TS2339: Property 'prop' does not exist on type '(n: number) => string'.
+tests/cases/conformance/salsa/typeFromPropertyAssignment29.ts(64,42): error TS2339: Property 'm' does not exist on type '(n: number) => string'.
+tests/cases/conformance/salsa/typeFromPropertyAssignment29.ts(70,14): error TS2339: Property 'prop' does not exist on type 'typeof ExpandoClass'.
+tests/cases/conformance/salsa/typeFromPropertyAssignment29.ts(71,14): error TS2339: Property 'm' does not exist on type 'typeof ExpandoClass'.
+tests/cases/conformance/salsa/typeFromPropertyAssignment29.ts(74,22): error TS2339: Property 'prop' does not exist on type 'typeof ExpandoClass'.
+tests/cases/conformance/salsa/typeFromPropertyAssignment29.ts(74,42): error TS2339: Property 'm' does not exist on type 'typeof ExpandoClass'.
+tests/cases/conformance/salsa/typeFromPropertyAssignment29.ts(80,14): error TS2339: Property 'prop' does not exist on type 'typeof ExpandoExpr3'.
+tests/cases/conformance/salsa/typeFromPropertyAssignment29.ts(81,14): error TS2339: Property 'm' does not exist on type 'typeof ExpandoExpr3'.
+tests/cases/conformance/salsa/typeFromPropertyAssignment29.ts(84,22): error TS2339: Property 'prop' does not exist on type 'typeof ExpandoExpr3'.
+tests/cases/conformance/salsa/typeFromPropertyAssignment29.ts(84,42): error TS2339: Property 'm' does not exist on type 'typeof ExpandoExpr3'.
 
 
 ==== tests/cases/conformance/salsa/typeFromPropertyAssignment29.ts (12 errors) ====
@@ -25,11 +25,12 @@ tests/cases/conformance/salsa/typeFromPropertyAssignment29.ts(54,42): error TS23
     const ExpandoExpr = function (n: number) {
         return n.toString();
     }
-    ExpandoExpr.prop = 2
+    ExpandoExpr.prop = { x: 2 }
+    ExpandoExpr.prop = { y: "" }
     ExpandoExpr.m = function(n: number) {
         return n + 1;
     }
-    var n = ExpandoExpr.prop + ExpandoExpr.m(12) + ExpandoExpr(101).length
+    var n = (ExpandoExpr.prop.x || 0) + ExpandoExpr.m(12) + ExpandoExpr(101).length
 
     const ExpandoArrow = (n: number) => n.toString();
     ExpandoArrow.prop = 2
@@ -38,6 +39,35 @@ tests/cases/conformance/salsa/typeFromPropertyAssignment29.ts(54,42): error TS23
 
     }
 
+    function ExpandoNested(n: number) {
+        const nested = function (m: number) {
+            return n + m;
+        };
+        nested.total = n + 1_000_000;
+        return nested;
+    }
+    ExpandoNested.also = -1;
+    
+    function ExpandoMerge(n: number) {
+        return n * 100;
+    }
+    ExpandoMerge.p1 = 111
+    namespace ExpandoMerge {
+        export var p2 = 222;
+    }
+    namespace ExpandoMerge {
+        export var p3 = 333;
+    }
+    var n = ExpandoMerge.p1 + ExpandoMerge.p2 + ExpandoMerge.p3 + ExpandoMerge(1);
+    
+    namespace Ns {
+        function ExpandoNamespace(): void {}
+        ExpandoNamespace.p6 = 42;
+        export function foo() {
+            return ExpandoNamespace;
+        }
+    }
+    
     // Should not work in Typescript -- must be const
     var ExpandoExpr2 = function (n: number) {
         return n.toString();

tests/baselines/reference/typeFromPropertyAssignment29.js

@@ -11,11 +11,12 @@ var n = ExpandoDecl.prop + ExpandoDecl.m(12) + ExpandoDecl(101).length
 const ExpandoExpr = function (n: number) {
     return n.toString();
 }
-ExpandoExpr.prop = 2
+ExpandoExpr.prop = { x: 2 }
+ExpandoExpr.prop = { y: "" }
 ExpandoExpr.m = function(n: number) {
     return n + 1;
 }
-var n = ExpandoExpr.prop + ExpandoExpr.m(12) + ExpandoExpr(101).length
+var n = (ExpandoExpr.prop.x || 0) + ExpandoExpr.m(12) + ExpandoExpr(101).length
 
 const ExpandoArrow = (n: number) => n.toString();
 ExpandoArrow.prop = 2
@@ -24,6 +25,35 @@ ExpandoArrow.m = function(n: number) {
 
 }
 
+function ExpandoNested(n: number) {
+    const nested = function (m: number) {
+        return n + m;
+    };
+    nested.total = n + 1_000_000;
+    return nested;
+}
+ExpandoNested.also = -1;
+
+function ExpandoMerge(n: number) {
+    return n * 100;
+}
+ExpandoMerge.p1 = 111
+namespace ExpandoMerge {
+    export var p2 = 222;
+}
+namespace ExpandoMerge {
+    export var p3 = 333;
+}
+var n = ExpandoMerge.p1 + ExpandoMerge.p2 + ExpandoMerge.p3 + ExpandoMerge(1);
+
+namespace Ns {
+    function ExpandoNamespace(): void {}
+    ExpandoNamespace.p6 = 42;
+    export function foo() {
+        return ExpandoNamespace;
+    }
+}
+
 // Should not work in Typescript -- must be const
 var ExpandoExpr2 = function (n: number) {
     return n.toString();
@@ -68,16 +98,45 @@ var n = ExpandoDecl.prop + ExpandoDecl.m(12) + ExpandoDecl(101).length;
 var ExpandoExpr = function (n) {
     return n.toString();
 };
-ExpandoExpr.prop = 2;
+ExpandoExpr.prop = { x: 2 };
+ExpandoExpr.prop = { y: "" };
 ExpandoExpr.m = function (n) {
     return n + 1;
 };
-var n = ExpandoExpr.prop + ExpandoExpr.m(12) + ExpandoExpr(101).length;
+var n = (ExpandoExpr.prop.x || 0) + ExpandoExpr.m(12) + ExpandoExpr(101).length;
 var ExpandoArrow = function (n) { return n.toString(); };
 ExpandoArrow.prop = 2;
 ExpandoArrow.m = function (n) {
     return n + 1;
 };
+function ExpandoNested(n) {
+    var nested = function (m) {
+        return n + m;
+    };
+    nested.total = n + 1000000;
+    return nested;
+}
+ExpandoNested.also = -1;
+function ExpandoMerge(n) {
+    return n * 100;
+}
+ExpandoMerge.p1 = 111;
+(function (ExpandoMerge) {
+    ExpandoMerge.p2 = 222;
+})(ExpandoMerge || (ExpandoMerge = {}));
+(function (ExpandoMerge) {
+    ExpandoMerge.p3 = 333;
+})(ExpandoMerge || (ExpandoMerge = {}));
+var n = ExpandoMerge.p1 + ExpandoMerge.p2 + ExpandoMerge.p3 + ExpandoMerge(1);
+var Ns;
+(function (Ns) {
+    function ExpandoNamespace() { }
+    ExpandoNamespace.p6 = 42;
+    function foo() {
+        return ExpandoNamespace;
+    }
+    Ns.foo = foo;
+})(Ns || (Ns = {}));
 // Should not work in Typescript -- must be const
 var ExpandoExpr2 = function (n) {
     return n.toString();
@@ -111,3 +170,66 @@ ExpandoExpr3.m = function (n) {
     return n + 1;
 };
 var n = ExpandoExpr3.prop + ExpandoExpr3.m(13) + new ExpandoExpr3().n;
+
+
+//// [typeFromPropertyAssignment29.d.ts]
+declare function ExpandoDecl(n: number): string;
+declare namespace ExpandoDecl {
+    var prop: number;
+    var m: (n: number) => number;
+}
+declare var n: number;
+declare const ExpandoExpr: {
+    (n: number): string;
+    prop: {
+        x: number;
+        y?: undefined;
+    } | {
+        y: string;
+        x?: undefined;
+    };
+    m(n: number): number;
+};
+declare var n: number;
+declare const ExpandoArrow: {
+    (n: number): string;
+    prop: number;
+    m(n: number): number;
+};
+declare function ExpandoNested(n: number): {
+    (m: number): number;
+    total: number;
+};
+declare namespace ExpandoNested {
+    var also: number;
+}
+declare function ExpandoMerge(n: number): number;
+declare namespace ExpandoMerge {
+    var p1: number;
+}
+declare namespace ExpandoMerge {
+    var p2: number;
+}
+declare namespace ExpandoMerge {
+    var p3: number;
+}
+declare var n: number;
+declare namespace Ns {
+    function ExpandoNamespace(): void;
+    namespace ExpandoNamespace {
+        var p6: number;
+    }
+    function foo(): typeof ExpandoNamespace;
+}
+declare var ExpandoExpr2: (n: number) => string;
+declare var n: number;
+declare class ExpandoClass {
+    n: number;
+}
+declare var n: number;
+declare var ExpandoExpr3: {
+    new (): {
+        n: number;
+    };
+};
+declare var n: number;