Report implict any error when widening null/undefined in presence of …

src/compiler/checker.ts

@@ -25513,7 +25513,7 @@ export function createTypeChecker(host: TypeCheckerHost): TypeChecker {
             case SyntaxKind.ArrowFunction:
                 if (noImplicitAny && !(declaration as NamedDeclaration).name) {
                     if (wideningKind === WideningKind.GeneratorYield) {
-                        error(declaration, Diagnostics.Generator_implicitly_has_yield_type_0_because_it_does_not_yield_any_values_Consider_supplying_a_return_type_annotation, typeAsString);
+                        error(declaration, Diagnostics.Generator_implicitly_has_yield_type_0_Consider_supplying_a_return_type_annotation, typeAsString);
                     }
                     else {
                         error(declaration, Diagnostics.Function_expression_which_lacks_return_type_annotation_implicitly_has_an_0_return_type, typeAsString);
@@ -25535,12 +25535,40 @@ export function createTypeChecker(host: TypeCheckerHost): TypeChecker {
         errorOrSuggestion(noImplicitAny, declaration, diagnostic, declarationNameToString(getNameOfDeclaration(declaration)), typeAsString);
     }
 
+    function shouldReportErrorsFromWideningWithContextualSignature(declaration: FunctionLikeDeclaration, wideningKind: WideningKind) {
+        const signature = getContextualSignatureForFunctionLikeDeclaration(declaration);
+        if (!signature) {
+            return true;
+        }
+        let returnType = getReturnTypeOfSignature(signature);
+        const flags = getFunctionFlags(declaration);
+        switch (wideningKind) {
+            case WideningKind.FunctionReturn:
+                if (flags & FunctionFlags.Generator) {
+                    returnType = getIterationTypeOfGeneratorFunctionReturnType(IterationTypeKind.Return, returnType, !!(flags & FunctionFlags.Async)) ?? returnType;
+                }
+                else if (flags & FunctionFlags.Async) {
+                    returnType = getAwaitedTypeNoAlias(returnType) ?? returnType;
+                }
+                return isGenericType(returnType);
+            case WideningKind.GeneratorYield:
+                const yieldType = getIterationTypeOfGeneratorFunctionReturnType(IterationTypeKind.Yield, returnType, !!(flags & FunctionFlags.Async));
+                return !!yieldType && isGenericType(yieldType);
+            case WideningKind.GeneratorNext:
+                const nextType = getIterationTypeOfGeneratorFunctionReturnType(IterationTypeKind.Next, returnType, !!(flags & FunctionFlags.Async));
+                return !!nextType && isGenericType(nextType);
+        }
+        return false;
+    }
+
     function reportErrorsFromWidening(declaration: Declaration, type: Type, wideningKind?: WideningKind) {
         addLazyDiagnostic(() => {
-            if (noImplicitAny && getObjectFlags(type) & ObjectFlags.ContainsWideningType && (!wideningKind || !getContextualSignatureForFunctionLikeDeclaration(declaration as FunctionLikeDeclaration))) {
-                // Report implicit any error within type if possible, otherwise report error on declaration
-                if (!reportWideningErrorsInType(type)) {
-                    reportImplicitAny(declaration, type, wideningKind);
+            if (noImplicitAny && getObjectFlags(type) & ObjectFlags.ContainsWideningType) {
+                if (!wideningKind || isFunctionLikeDeclaration(declaration) && shouldReportErrorsFromWideningWithContextualSignature(declaration, wideningKind)) {
+                    // Report implicit any error within type if possible, otherwise report error on declaration
+                    if (!reportWideningErrorsInType(type)) {
+                        reportImplicitAny(declaration, type, wideningKind);
+                    }
                 }
             }
         });

src/compiler/diagnosticMessages.json

@@ -6626,7 +6626,7 @@
         "category": "Error",
         "code": 7024
     },
-    "Generator implicitly has yield type '{0}' because it does not yield any values. Consider supplying a return type annotation.": {
+    "Generator implicitly has yield type '{0}'. Consider supplying a return type annotation.": {
         "category": "Error",
         "code": 7025
     },

tests/baselines/reference/generatorReturnTypeInferenceNonStrict.errors.txt

@@ -4,7 +4,7 @@ generatorReturnTypeInferenceNonStrict.ts(74,15): error TS7057: 'yield' expressio
 generatorReturnTypeInferenceNonStrict.ts(79,11): error TS7055: 'g301', which lacks return-type annotation, implicitly has an 'any' yield type.
 generatorReturnTypeInferenceNonStrict.ts(89,11): error TS7055: 'g303', which lacks return-type annotation, implicitly has an 'any' yield type.
 generatorReturnTypeInferenceNonStrict.ts(126,11): error TS7055: 'g310', which lacks return-type annotation, implicitly has an 'any' yield type.
-generatorReturnTypeInferenceNonStrict.ts(131,10): error TS7025: Generator implicitly has yield type 'any' because it does not yield any values. Consider supplying a return type annotation.
+generatorReturnTypeInferenceNonStrict.ts(131,10): error TS7025: Generator implicitly has yield type 'any'. Consider supplying a return type annotation.
 
 
 ==== generatorReturnTypeInferenceNonStrict.ts (7 errors) ====
@@ -152,7 +152,7 @@ generatorReturnTypeInferenceNonStrict.ts(131,10): error TS7025: Generator implic
     function* g311() { // Generator<any (implicit), void, string>
     	yield* (function*() {
     	        ~~~~~~~~
-!!! error TS7025: Generator implicitly has yield type 'any' because it does not yield any values. Consider supplying a return type annotation.
+!!! error TS7025: Generator implicitly has yield type 'any'. Consider supplying a return type annotation.
     		const y: string = yield;
     	})();
     }

tests/baselines/reference/generatorTypeCheck62.errors.txt

@@ -12,9 +12,10 @@ generatorTypeCheck62.ts(32,62): error TS2345: Argument of type '(state: State) =
         Type 'IteratorReturnResult<State>' is not assignable to type 'IteratorResult<any, void>'.
           Type 'IteratorReturnResult<State>' is not assignable to type 'IteratorReturnResult<void>'.
             Type 'State' is not assignable to type 'void'.
+generatorTypeCheck62.ts(32,62): error TS7025: Generator implicitly has yield type 'any'. Consider supplying a return type annotation.
 
 
-==== generatorTypeCheck62.ts (2 errors) ====
+==== generatorTypeCheck62.ts (3 errors) ====
     export interface StrategicState {
         lastStrategyApplied?: string;
     }
@@ -63,6 +64,8 @@ generatorTypeCheck62.ts(32,62): error TS2345: Argument of type '(state: State) =
 !!! error TS2345:         Type 'IteratorReturnResult<State>' is not assignable to type 'IteratorResult<any, void>'.
 !!! error TS2345:           Type 'IteratorReturnResult<State>' is not assignable to type 'IteratorReturnResult<void>'.
 !!! error TS2345:             Type 'State' is not assignable to type 'void'.
+                                                                 ~~~~~~~~
+!!! error TS7025: Generator implicitly has yield type 'any'. Consider supplying a return type annotation.
         yield ;
         return state; // `return`/`TReturn` isn't supported by `strategy`, so this should error.
     });

tests/baselines/reference/implicitAnyGenericTypeInference.errors.txt

@@ -0,0 +1,56 @@
+implicitAnyGenericTypeInference.ts(10,4): error TS7011: Function expression, which lacks return-type annotation, implicitly has an 'any' return type.
+implicitAnyGenericTypeInference.ts(13,4): error TS7011: Function expression, which lacks return-type annotation, implicitly has an 'any' return type.
+implicitAnyGenericTypeInference.ts(16,4): error TS7025: Generator implicitly has yield type 'any'. Consider supplying a return type annotation.
+implicitAnyGenericTypeInference.ts(19,4): error TS7011: Function expression, which lacks return-type annotation, implicitly has an 'any' return type.
+implicitAnyGenericTypeInference.ts(22,4): error TS7025: Generator implicitly has yield type 'any'. Consider supplying a return type annotation.
+implicitAnyGenericTypeInference.ts(25,4): error TS7011: Function expression, which lacks return-type annotation, implicitly has an 'any' return type.
+implicitAnyGenericTypeInference.ts(28,25): error TS7011: Function expression, which lacks return-type annotation, implicitly has an 'any' return type.
+implicitAnyGenericTypeInference.ts(29,24): error TS7011: Function expression, which lacks return-type annotation, implicitly has an 'any' return type.
+
+
+==== implicitAnyGenericTypeInference.ts (8 errors) ====
+    interface Comparer<T> {
+        compareTo<U>(x: T, y: U): U;
+    }
+
+    var c: Comparer<any>;
+    c = { compareTo: (x, y) => { return y; } };
+    var r = c.compareTo(1, '');
+
+    declare function f1<T>(cb: () => T): void;
+    f1(() => null);
+       ~~~~~~~~~~
+!!! error TS7011: Function expression, which lacks return-type annotation, implicitly has an 'any' return type.
+
+    declare function f2<T>(cb: () => PromiseLike<T>): void;
+    f2(async () => null);
+       ~~~~~~~~~~~~~~~~
+!!! error TS7011: Function expression, which lacks return-type annotation, implicitly has an 'any' return type.
+
+    declare function f3<T>(cb: () => Generator<T>): void;
+    f3(function* () { yield null; });
+       ~~~~~~~~
+!!! error TS7025: Generator implicitly has yield type 'any'. Consider supplying a return type annotation.
+
+    declare function f4<T>(cb: () => Generator<unknown, T>): void;
+    f4(function* () { return null; });
+       ~~~~~~~~
+!!! error TS7011: Function expression, which lacks return-type annotation, implicitly has an 'any' return type.
+
+    declare function f5<T>(cb: () => AsyncGenerator<T>): void;
+    f5(async function* () { yield null; });
+       ~~~~~
+!!! error TS7025: Generator implicitly has yield type 'any'. Consider supplying a return type annotation.
+
+    declare function f6<T>(cb: () => AsyncGenerator<unknown, T>): void;
+    f6(async function* () { return null; });
+       ~~~~~
+!!! error TS7011: Function expression, which lacks return-type annotation, implicitly has an 'any' return type.
+
+    // https://github.com/microsoft/TypeScript/issues/44913
+    Promise.resolve().catch(e => null);
+                            ~~~~~~~~~
+!!! error TS7011: Function expression, which lacks return-type annotation, implicitly has an 'any' return type.
+    Promise.resolve().then(v => null);
+                           ~~~~~~~~~
+!!! error TS7011: Function expression, which lacks return-type annotation, implicitly has an 'any' return type.

tests/baselines/reference/implicitAnyGenericTypeInference.js

@@ -7,9 +7,40 @@ interface Comparer<T> {
 
 var c: Comparer<any>;
 c = { compareTo: (x, y) => { return y; } };
-var r = c.compareTo(1, '');
+var r = c.compareTo(1, '');
+
+declare function f1<T>(cb: () => T): void;
+f1(() => null);
+
+declare function f2<T>(cb: () => PromiseLike<T>): void;
+f2(async () => null);
+
+declare function f3<T>(cb: () => Generator<T>): void;
+f3(function* () { yield null; });
+
+declare function f4<T>(cb: () => Generator<unknown, T>): void;
+f4(function* () { return null; });
+
+declare function f5<T>(cb: () => AsyncGenerator<T>): void;
+f5(async function* () { yield null; });
+
+declare function f6<T>(cb: () => AsyncGenerator<unknown, T>): void;
+f6(async function* () { return null; });
+
+// https://github.com/microsoft/TypeScript/issues/44913
+Promise.resolve().catch(e => null);
+Promise.resolve().then(v => null);
 
 //// [implicitAnyGenericTypeInference.js]
 var c;
-c = { compareTo: function (x, y) { return y; } };
+c = { compareTo: (x, y) => { return y; } };
 var r = c.compareTo(1, '');
+f1(() => null);
+f2(async () => null);
+f3(function* () { yield null; });
+f4(function* () { return null; });
+f5(async function* () { yield null; });
+f6(async function* () { return null; });
+// https://github.com/microsoft/TypeScript/issues/44913
+Promise.resolve().catch(e => null);
+Promise.resolve().then(v => null);

tests/baselines/reference/implicitAnyGenericTypeInference.symbols

@@ -32,3 +32,79 @@ var r = c.compareTo(1, '');
 >c : Symbol(c, Decl(implicitAnyGenericTypeInference.ts, 4, 3))
 >compareTo : Symbol(Comparer.compareTo, Decl(implicitAnyGenericTypeInference.ts, 0, 23))
 
+declare function f1<T>(cb: () => T): void;
+>f1 : Symbol(f1, Decl(implicitAnyGenericTypeInference.ts, 6, 27))
+>T : Symbol(T, Decl(implicitAnyGenericTypeInference.ts, 8, 20))
+>cb : Symbol(cb, Decl(implicitAnyGenericTypeInference.ts, 8, 23))
+>T : Symbol(T, Decl(implicitAnyGenericTypeInference.ts, 8, 20))
+
+f1(() => null);
+>f1 : Symbol(f1, Decl(implicitAnyGenericTypeInference.ts, 6, 27))
+
+declare function f2<T>(cb: () => PromiseLike<T>): void;
+>f2 : Symbol(f2, Decl(implicitAnyGenericTypeInference.ts, 9, 15))
+>T : Symbol(T, Decl(implicitAnyGenericTypeInference.ts, 11, 20))
+>cb : Symbol(cb, Decl(implicitAnyGenericTypeInference.ts, 11, 23))
+>PromiseLike : Symbol(PromiseLike, Decl(lib.es5.d.ts, --, --))
+>T : Symbol(T, Decl(implicitAnyGenericTypeInference.ts, 11, 20))
+
+f2(async () => null);
+>f2 : Symbol(f2, Decl(implicitAnyGenericTypeInference.ts, 9, 15))
+
+declare function f3<T>(cb: () => Generator<T>): void;
+>f3 : Symbol(f3, Decl(implicitAnyGenericTypeInference.ts, 12, 21))
+>T : Symbol(T, Decl(implicitAnyGenericTypeInference.ts, 14, 20))
+>cb : Symbol(cb, Decl(implicitAnyGenericTypeInference.ts, 14, 23))
+>Generator : Symbol(Generator, Decl(lib.es2015.generator.d.ts, --, --))
+>T : Symbol(T, Decl(implicitAnyGenericTypeInference.ts, 14, 20))
+
+f3(function* () { yield null; });
+>f3 : Symbol(f3, Decl(implicitAnyGenericTypeInference.ts, 12, 21))
+
+declare function f4<T>(cb: () => Generator<unknown, T>): void;
+>f4 : Symbol(f4, Decl(implicitAnyGenericTypeInference.ts, 15, 33))
+>T : Symbol(T, Decl(implicitAnyGenericTypeInference.ts, 17, 20))
+>cb : Symbol(cb, Decl(implicitAnyGenericTypeInference.ts, 17, 23))
+>Generator : Symbol(Generator, Decl(lib.es2015.generator.d.ts, --, --))
+>T : Symbol(T, Decl(implicitAnyGenericTypeInference.ts, 17, 20))
+
+f4(function* () { return null; });
+>f4 : Symbol(f4, Decl(implicitAnyGenericTypeInference.ts, 15, 33))
+
+declare function f5<T>(cb: () => AsyncGenerator<T>): void;
+>f5 : Symbol(f5, Decl(implicitAnyGenericTypeInference.ts, 18, 34))
+>T : Symbol(T, Decl(implicitAnyGenericTypeInference.ts, 20, 20))
+>cb : Symbol(cb, Decl(implicitAnyGenericTypeInference.ts, 20, 23))
+>AsyncGenerator : Symbol(AsyncGenerator, Decl(lib.es2018.asyncgenerator.d.ts, --, --))
+>T : Symbol(T, Decl(implicitAnyGenericTypeInference.ts, 20, 20))
+
+f5(async function* () { yield null; });
+>f5 : Symbol(f5, Decl(implicitAnyGenericTypeInference.ts, 18, 34))
+
+declare function f6<T>(cb: () => AsyncGenerator<unknown, T>): void;
+>f6 : Symbol(f6, Decl(implicitAnyGenericTypeInference.ts, 21, 39))
+>T : Symbol(T, Decl(implicitAnyGenericTypeInference.ts, 23, 20))
+>cb : Symbol(cb, Decl(implicitAnyGenericTypeInference.ts, 23, 23))
+>AsyncGenerator : Symbol(AsyncGenerator, Decl(lib.es2018.asyncgenerator.d.ts, --, --))
+>T : Symbol(T, Decl(implicitAnyGenericTypeInference.ts, 23, 20))
+
+f6(async function* () { return null; });
+>f6 : Symbol(f6, Decl(implicitAnyGenericTypeInference.ts, 21, 39))
+
+// https://github.com/microsoft/TypeScript/issues/44913
+Promise.resolve().catch(e => null);
+>Promise.resolve().catch : Symbol(Promise.catch, Decl(lib.es5.d.ts, --, --))
+>Promise.resolve : Symbol(PromiseConstructor.resolve, Decl(lib.es2015.promise.d.ts, --, --), Decl(lib.es2015.promise.d.ts, --, --), Decl(lib.es2015.promise.d.ts, --, --))
+>Promise : Symbol(Promise, Decl(lib.es5.d.ts, --, --), Decl(lib.es2015.iterable.d.ts, --, --), Decl(lib.es2015.promise.d.ts, --, --), Decl(lib.es2015.symbol.wellknown.d.ts, --, --), Decl(lib.es2018.promise.d.ts, --, --))
+>resolve : Symbol(PromiseConstructor.resolve, Decl(lib.es2015.promise.d.ts, --, --), Decl(lib.es2015.promise.d.ts, --, --), Decl(lib.es2015.promise.d.ts, --, --))
+>catch : Symbol(Promise.catch, Decl(lib.es5.d.ts, --, --))
+>e : Symbol(e, Decl(implicitAnyGenericTypeInference.ts, 27, 24))
+
+Promise.resolve().then(v => null);
+>Promise.resolve().then : Symbol(Promise.then, Decl(lib.es5.d.ts, --, --))
+>Promise.resolve : Symbol(PromiseConstructor.resolve, Decl(lib.es2015.promise.d.ts, --, --), Decl(lib.es2015.promise.d.ts, --, --), Decl(lib.es2015.promise.d.ts, --, --))
+>Promise : Symbol(Promise, Decl(lib.es5.d.ts, --, --), Decl(lib.es2015.iterable.d.ts, --, --), Decl(lib.es2015.promise.d.ts, --, --), Decl(lib.es2015.symbol.wellknown.d.ts, --, --), Decl(lib.es2018.promise.d.ts, --, --))
+>resolve : Symbol(PromiseConstructor.resolve, Decl(lib.es2015.promise.d.ts, --, --), Decl(lib.es2015.promise.d.ts, --, --), Decl(lib.es2015.promise.d.ts, --, --))
+>then : Symbol(Promise.then, Decl(lib.es5.d.ts, --, --))
+>v : Symbol(v, Decl(implicitAnyGenericTypeInference.ts, 28, 23))
+