Improve check of whether type query node possibly contains reference to type parameter

src/compiler/checker.ts

@@ -728,6 +728,7 @@ namespace ts {
             isPropertyAccessible,
             getTypeOnlyAliasDeclaration,
             getMemberOverrideModifierStatus,
+            isTypeParameterPossiblyReferenced,
         };
 
         function runWithInferenceBlockedFromSourceNode<T>(node: Node | undefined, fn: () => T): T {
@@ -17193,9 +17194,10 @@ namespace ts {
         }
 
         function isTypeParameterPossiblyReferenced(tp: TypeParameter, node: Node) {
-            // If the type parameter doesn't have exactly one declaration, if there are invening statement blocks
+            // If the type parameter doesn't have exactly one declaration, if there are intervening statement blocks
             // between the node and the type parameter declaration, if the node contains actual references to the
-            // type parameter, or if the node contains type queries, we consider the type parameter possibly referenced.
+            // type parameter, or if the node contains type queries that we can't prove couldn't contain references to the type parameter,
+            // we consider the type parameter possibly referenced.
             if (tp.symbol && tp.symbol.declarations && tp.symbol.declarations.length === 1) {
                 const container = tp.symbol.declarations[0].parent;
                 for (let n = node; n !== container; n = n.parent) {
@@ -17214,6 +17216,28 @@ namespace ts {
                         return !tp.isThisType && isPartOfTypeNode(node) && maybeTypeParameterReference(node) &&
                             getTypeFromTypeNodeWorker(node as TypeNode) === tp; // use worker because we're looking for === equality
                     case SyntaxKind.TypeQuery:
+                        const entityName = (node as TypeQueryNode).exprName;
+                        const firstIdentifier = getFirstIdentifier(entityName);
+                        const firstIdentifierSymbol = getResolvedSymbol(firstIdentifier);
+                        const tpDeclaration = tp.symbol.declarations![0]; // There is exactly one declaration, otherwise `containsReference` is not called
+                        let tpScope: Node;
+                        if (tpDeclaration.kind === SyntaxKind.TypeParameter) { // Type parameter is a regular type parameter, e.g. foo<T>
+                            tpScope = tpDeclaration.parent;
+                        }
+                        else if (tp.isThisType) {
+                             // Type parameter is the this type, and its declaration is the class declaration.
+                            tpScope = tpDeclaration;
+                        }
+                        else {
+                            // Type parameter's declaration was unrecognized.
+                            // This could happen if the type parameter comes from e.g. a JSDoc annotation, so we default to returning true.
+                            return true;
+                        }
+
+                        if (firstIdentifierSymbol.declarations) {
+                            return some(firstIdentifierSymbol.declarations, idDecl => isNodeDescendantOf(idDecl, tpScope)) ||
+                                some((node as TypeQueryNode).typeArguments, containsReference);
+                        }
                         return true;
                     case SyntaxKind.MethodDeclaration:
                     case SyntaxKind.MethodSignature:

src/compiler/types.ts

@@ -4854,6 +4854,7 @@ namespace ts {
         /* @internal */ isPropertyAccessible(node: Node, isSuper: boolean, isWrite: boolean, containingType: Type, property: Symbol): boolean;
         /* @internal */ getTypeOnlyAliasDeclaration(symbol: Symbol): TypeOnlyAliasDeclaration | undefined;
         /* @internal */ getMemberOverrideModifierStatus(node: ClassLikeDeclaration, member: ClassElement): MemberOverrideStatus;
+        /* @internal */ isTypeParameterPossiblyReferenced(tp: TypeParameter, node: Node): boolean;
     }
 
     /* @internal */

src/testRunner/tsconfig.json

@@ -76,6 +76,7 @@
         "unittests/reuseProgramStructure.ts",
         "unittests/semver.ts",
         "unittests/transform.ts",
+        "unittests/typeParameterIsPossiblyReferenced.ts",
         "unittests/config/commandLineParsing.ts",
         "unittests/config/configurationExtension.ts",
         "unittests/config/convertCompilerOptionsFromJson.ts",

src/testRunner/unittests/typeParameterIsPossiblyReferenced.ts

@@ -0,0 +1,33 @@
+describe("unittests :: internalApi :: typeParameterIsPossiblyReferenced", () => {
+        it("with type parameter aliasing", () => {
+            const content = `
+            declare function foo<T>(b: T, f: <T>(a: typeof b) => typeof a): typeof f;
+            `;
+            const host = new fakes.CompilerHost(vfs.createFromFileSystem(
+                Harness.IO,
+                /*ignoreCases*/ true,
+                {
+                    documents: [
+                        new documents.TextDocument("/file.ts", content)
+                    ],
+                    cwd: "/",
+                }
+            ));
+            const program = ts.createProgram({
+                host,
+                rootNames: ["/file.ts"],
+                options: { strict: true },
+            });
+            const checker = program.getTypeChecker();
+            const file = program.getSourceFile("/file.ts")!;
+            const typeQueryNode = (((file.statements[0] as ts.FunctionDeclaration) // function f<T>
+                .parameters[1] // f
+                .type! as ts.FunctionTypeNode) // <T>(a: typeof b) => typeof a
+                .type as ts.TypeQueryNode) // typeof a
+                ;
+            const typeParameterDecl = (file.statements[0] as ts.FunctionDeclaration).typeParameters![0]; // T in f<T>
+            const typeParameter = checker.getTypeAtLocation(typeParameterDecl)! as ts.TypeParameter;
+            const isReferenced = checker.isTypeParameterPossiblyReferenced(typeParameter, typeQueryNode);
+            assert.ok(isReferenced, "Type parameter is referenced in type query node");
+        });
+});

tests/baselines/reference/typeofObjectInference.js

@@ -0,0 +1,51 @@
+//// [typeofObjectInference.ts]
+let val = 1
+
+function decorateA<O extends any>(fn: (first: {value: typeof val}) => O) {
+    return (): O => fn({value: val})
+}
+let a = decorateA(({value}) => 5)
+
+function decorateB<O extends any>(fn: (first: typeof val) => O) {
+    return (): O => fn(val)
+}
+let b = decorateB((value) => 5)
+
+function decorateC<O extends any>(fn: (first: {value: number}) => O) {
+    return (): O => fn({value: val})
+}
+let c = decorateC(({value}) => 5)
+
+type First = {value: typeof val}
+function decorateD<O extends any>(fn: (first: First) => O) {
+    return (): O => fn({value: val})
+}
+let d = decorateD(({value}) => 5)
+
+//// [typeofObjectInference.js]
+var val = 1;
+function decorateA(fn) {
+    return function () { return fn({ value: val }); };
+}
+var a = decorateA(function (_a) {
+    var value = _a.value;
+    return 5;
+});
+function decorateB(fn) {
+    return function () { return fn(val); };
+}
+var b = decorateB(function (value) { return 5; });
+function decorateC(fn) {
+    return function () { return fn({ value: val }); };
+}
+var c = decorateC(function (_a) {
+    var value = _a.value;
+    return 5;
+});
+function decorateD(fn) {
+    return function () { return fn({ value: val }); };
+}
+var d = decorateD(function (_a) {
+    var value = _a.value;
+    return 5;
+});

tests/baselines/reference/typeofObjectInference.symbols

@@ -0,0 +1,85 @@
+=== tests/cases/compiler/typeofObjectInference.ts ===
+let val = 1
+>val : Symbol(val, Decl(typeofObjectInference.ts, 0, 3))
+
+function decorateA<O extends any>(fn: (first: {value: typeof val}) => O) {
+>decorateA : Symbol(decorateA, Decl(typeofObjectInference.ts, 0, 11))
+>O : Symbol(O, Decl(typeofObjectInference.ts, 2, 19))
+>fn : Symbol(fn, Decl(typeofObjectInference.ts, 2, 34))
+>first : Symbol(first, Decl(typeofObjectInference.ts, 2, 39))
+>value : Symbol(value, Decl(typeofObjectInference.ts, 2, 47))
+>val : Symbol(val, Decl(typeofObjectInference.ts, 0, 3))
+>O : Symbol(O, Decl(typeofObjectInference.ts, 2, 19))
+
+    return (): O => fn({value: val})
+>O : Symbol(O, Decl(typeofObjectInference.ts, 2, 19))
+>fn : Symbol(fn, Decl(typeofObjectInference.ts, 2, 34))
+>value : Symbol(value, Decl(typeofObjectInference.ts, 3, 24))
+>val : Symbol(val, Decl(typeofObjectInference.ts, 0, 3))
+}
+let a = decorateA(({value}) => 5)
+>a : Symbol(a, Decl(typeofObjectInference.ts, 5, 3))
+>decorateA : Symbol(decorateA, Decl(typeofObjectInference.ts, 0, 11))
+>value : Symbol(value, Decl(typeofObjectInference.ts, 5, 20))
+
+function decorateB<O extends any>(fn: (first: typeof val) => O) {
+>decorateB : Symbol(decorateB, Decl(typeofObjectInference.ts, 5, 33))
+>O : Symbol(O, Decl(typeofObjectInference.ts, 7, 19))
+>fn : Symbol(fn, Decl(typeofObjectInference.ts, 7, 34))
+>first : Symbol(first, Decl(typeofObjectInference.ts, 7, 39))
+>val : Symbol(val, Decl(typeofObjectInference.ts, 0, 3))
+>O : Symbol(O, Decl(typeofObjectInference.ts, 7, 19))
+
+    return (): O => fn(val)
+>O : Symbol(O, Decl(typeofObjectInference.ts, 7, 19))
+>fn : Symbol(fn, Decl(typeofObjectInference.ts, 7, 34))
+>val : Symbol(val, Decl(typeofObjectInference.ts, 0, 3))
+}
+let b = decorateB((value) => 5)
+>b : Symbol(b, Decl(typeofObjectInference.ts, 10, 3))
+>decorateB : Symbol(decorateB, Decl(typeofObjectInference.ts, 5, 33))
+>value : Symbol(value, Decl(typeofObjectInference.ts, 10, 19))
+
+function decorateC<O extends any>(fn: (first: {value: number}) => O) {
+>decorateC : Symbol(decorateC, Decl(typeofObjectInference.ts, 10, 31))
+>O : Symbol(O, Decl(typeofObjectInference.ts, 12, 19))
+>fn : Symbol(fn, Decl(typeofObjectInference.ts, 12, 34))
+>first : Symbol(first, Decl(typeofObjectInference.ts, 12, 39))
+>value : Symbol(value, Decl(typeofObjectInference.ts, 12, 47))
+>O : Symbol(O, Decl(typeofObjectInference.ts, 12, 19))
+
+    return (): O => fn({value: val})
+>O : Symbol(O, Decl(typeofObjectInference.ts, 12, 19))
+>fn : Symbol(fn, Decl(typeofObjectInference.ts, 12, 34))
+>value : Symbol(value, Decl(typeofObjectInference.ts, 13, 24))
+>val : Symbol(val, Decl(typeofObjectInference.ts, 0, 3))
+}
+let c = decorateC(({value}) => 5)
+>c : Symbol(c, Decl(typeofObjectInference.ts, 15, 3))
+>decorateC : Symbol(decorateC, Decl(typeofObjectInference.ts, 10, 31))
+>value : Symbol(value, Decl(typeofObjectInference.ts, 15, 20))
+
+type First = {value: typeof val}
+>First : Symbol(First, Decl(typeofObjectInference.ts, 15, 33))
+>value : Symbol(value, Decl(typeofObjectInference.ts, 17, 14))
+>val : Symbol(val, Decl(typeofObjectInference.ts, 0, 3))
+
+function decorateD<O extends any>(fn: (first: First) => O) {
+>decorateD : Symbol(decorateD, Decl(typeofObjectInference.ts, 17, 32))
+>O : Symbol(O, Decl(typeofObjectInference.ts, 18, 19))
+>fn : Symbol(fn, Decl(typeofObjectInference.ts, 18, 34))
+>first : Symbol(first, Decl(typeofObjectInference.ts, 18, 39))
+>First : Symbol(First, Decl(typeofObjectInference.ts, 15, 33))
+>O : Symbol(O, Decl(typeofObjectInference.ts, 18, 19))
+
+    return (): O => fn({value: val})
+>O : Symbol(O, Decl(typeofObjectInference.ts, 18, 19))
+>fn : Symbol(fn, Decl(typeofObjectInference.ts, 18, 34))
+>value : Symbol(value, Decl(typeofObjectInference.ts, 19, 24))
+>val : Symbol(val, Decl(typeofObjectInference.ts, 0, 3))
+}
+let d = decorateD(({value}) => 5)
+>d : Symbol(d, Decl(typeofObjectInference.ts, 21, 3))
+>decorateD : Symbol(decorateD, Decl(typeofObjectInference.ts, 17, 32))
+>value : Symbol(value, Decl(typeofObjectInference.ts, 21, 20))
+

tests/baselines/reference/typeofObjectInference.types

@@ -0,0 +1,96 @@
+=== tests/cases/compiler/typeofObjectInference.ts ===
+let val = 1
+>val : number
+>1 : 1
+
+function decorateA<O extends any>(fn: (first: {value: typeof val}) => O) {
+>decorateA : <O extends unknown>(fn: (first: {    value: typeof val;}) => O) => () => O
+>fn : (first: {    value: typeof val;}) => O
+>first : { value: typeof val; }
+>value : number
+>val : number
+
+    return (): O => fn({value: val})
+>(): O => fn({value: val}) : () => O
+>fn({value: val}) : O
+>fn : (first: { value: number; }) => O
+>{value: val} : { value: number; }
+>value : number
+>val : number
+}
+let a = decorateA(({value}) => 5)
+>a : () => number
+>decorateA(({value}) => 5) : () => number
+>decorateA : <O extends unknown>(fn: (first: { value: number; }) => O) => () => O
+>({value}) => 5 : ({ value }: { value: number; }) => number
+>value : number
+>5 : 5
+
+function decorateB<O extends any>(fn: (first: typeof val) => O) {
+>decorateB : <O extends unknown>(fn: (first: typeof val) => O) => () => O
+>fn : (first: typeof val) => O
+>first : number
+>val : number
+
+    return (): O => fn(val)
+>(): O => fn(val) : () => O
+>fn(val) : O
+>fn : (first: number) => O
+>val : number
+}
+let b = decorateB((value) => 5)
+>b : () => number
+>decorateB((value) => 5) : () => number
+>decorateB : <O extends unknown>(fn: (first: number) => O) => () => O
+>(value) => 5 : (value: number) => number
+>value : number
+>5 : 5
+
+function decorateC<O extends any>(fn: (first: {value: number}) => O) {
+>decorateC : <O extends unknown>(fn: (first: {    value: number;}) => O) => () => O
+>fn : (first: {    value: number;}) => O
+>first : { value: number; }
+>value : number
+
+    return (): O => fn({value: val})
+>(): O => fn({value: val}) : () => O
+>fn({value: val}) : O
+>fn : (first: { value: number; }) => O
+>{value: val} : { value: number; }
+>value : number
+>val : number
+}
+let c = decorateC(({value}) => 5)
+>c : () => number
+>decorateC(({value}) => 5) : () => number
+>decorateC : <O extends unknown>(fn: (first: { value: number; }) => O) => () => O
+>({value}) => 5 : ({ value }: { value: number; }) => number
+>value : number
+>5 : 5
+
+type First = {value: typeof val}
+>First : { value: typeof val; }
+>value : number
+>val : number
+
+function decorateD<O extends any>(fn: (first: First) => O) {
+>decorateD : <O extends unknown>(fn: (first: First) => O) => () => O
+>fn : (first: First) => O
+>first : First
+
+    return (): O => fn({value: val})
+>(): O => fn({value: val}) : () => O
+>fn({value: val}) : O
+>fn : (first: First) => O
+>{value: val} : { value: number; }
+>value : number
+>val : number
+}
+let d = decorateD(({value}) => 5)
+>d : () => number
+>decorateD(({value}) => 5) : () => number
+>decorateD : <O extends unknown>(fn: (first: First) => O) => () => O
+>({value}) => 5 : ({ value }: First) => number
+>value : number
+>5 : 5
+

tests/cases/compiler/typeofObjectInference.ts

@@ -0,0 +1,22 @@
+let val = 1
+
+function decorateA<O extends any>(fn: (first: {value: typeof val}) => O) {
+    return (): O => fn({value: val})
+}
+let a = decorateA(({value}) => 5)
+
+function decorateB<O extends any>(fn: (first: typeof val) => O) {
+    return (): O => fn(val)
+}
+let b = decorateB((value) => 5)
+
+function decorateC<O extends any>(fn: (first: {value: number}) => O) {
+    return (): O => fn({value: val})
+}
+let c = decorateC(({value}) => 5)
+
+type First = {value: typeof val}
+function decorateD<O extends any>(fn: (first: First) => O) {
+    return (): O => fn({value: val})
+}
+let d = decorateD(({value}) => 5)