Merge pull request microsoft#30856 from Microsoft/nonInferrableType

Add a proper non-inferrable type

Author: ahejlsberg

src/compiler/checker.ts

@@ -403,10 +403,10 @@ namespace ts {
         const wildcardType = createIntrinsicType(TypeFlags.Any, "any");
         const errorType = createIntrinsicType(TypeFlags.Any, "error");
         const unknownType = createIntrinsicType(TypeFlags.Unknown, "unknown");
-        const undefinedType = createNullableType(TypeFlags.Undefined, "undefined", 0);
-        const undefinedWideningType = strictNullChecks ? undefinedType : createNullableType(TypeFlags.Undefined, "undefined", ObjectFlags.ContainsWideningType);
-        const nullType = createNullableType(TypeFlags.Null, "null", 0);
-        const nullWideningType = strictNullChecks ? nullType : createNullableType(TypeFlags.Null, "null", ObjectFlags.ContainsWideningType);
+        const undefinedType = createIntrinsicType(TypeFlags.Undefined, "undefined");
+        const undefinedWideningType = strictNullChecks ? undefinedType : createIntrinsicType(TypeFlags.Undefined, "undefined", ObjectFlags.ContainsWideningType);
+        const nullType = createIntrinsicType(TypeFlags.Null, "null");
+        const nullWideningType = strictNullChecks ? nullType : createIntrinsicType(TypeFlags.Null, "null", ObjectFlags.ContainsWideningType);
         const stringType = createIntrinsicType(TypeFlags.String, "string");
         const numberType = createIntrinsicType(TypeFlags.Number, "number");
         const bigintType = createIntrinsicType(TypeFlags.BigInt, "bigint");
@@ -432,6 +432,7 @@ namespace ts {
         const voidType = createIntrinsicType(TypeFlags.Void, "void");
         const neverType = createIntrinsicType(TypeFlags.Never, "never");
         const silentNeverType = createIntrinsicType(TypeFlags.Never, "never");
+        const nonInferrableType = createIntrinsicType(TypeFlags.Never, "never", ObjectFlags.NonInferrableType);
         const implicitNeverType = createIntrinsicType(TypeFlags.Never, "never");
         const nonPrimitiveType = createIntrinsicType(TypeFlags.NonPrimitive, "object");
         const stringNumberSymbolType = getUnionType([stringType, numberType, esSymbolType]);
@@ -452,7 +453,7 @@ namespace ts {
         const anyFunctionType = createAnonymousType(undefined, emptySymbols, emptyArray, emptyArray, undefined, undefined);
         // The anyFunctionType contains the anyFunctionType by definition. The flag is further propagated
         // in getPropagatingFlagsOfTypes, and it is checked in inferFromTypes.
-        anyFunctionType.objectFlags |= ObjectFlags.ContainsAnyFunctionType;
+        anyFunctionType.objectFlags |= ObjectFlags.NonInferrableType;
 
         const noConstraintType = createAnonymousType(undefined, emptySymbols, emptyArray, emptyArray, undefined, undefined);
         const circularConstraintType = createAnonymousType(undefined, emptySymbols, emptyArray, emptyArray, undefined, undefined);
@@ -2753,14 +2754,9 @@ namespace ts {
             return result;
         }
 
-        function createIntrinsicType(kind: TypeFlags, intrinsicName: string): IntrinsicType {
+        function createIntrinsicType(kind: TypeFlags, intrinsicName: string, objectFlags: ObjectFlags = 0): IntrinsicType {
             const type = <IntrinsicType>createType(kind);
             type.intrinsicName = intrinsicName;
-            return type;
-        }
-
-        function createNullableType(kind: TypeFlags, intrinsicName: string, objectFlags: ObjectFlags): NullableType {
-            const type = createIntrinsicType(kind, intrinsicName);
             type.objectFlags = objectFlags;
             return type;
         }
@@ -14455,16 +14451,10 @@ namespace ts {
         }
 
         function createReverseMappedType(source: Type, target: MappedType, constraint: IndexType) {
-            const properties = getPropertiesOfType(source);
-            if (properties.length === 0 && !getIndexInfoOfType(source, IndexKind.String)) {
-                return undefined;
-            }
             // If any property contains context sensitive functions that have been skipped, the source type
             // is incomplete and we can't infer a meaningful input type.
-            for (const prop of properties) {
-                if (getObjectFlags(getTypeOfSymbol(prop)) & ObjectFlags.ContainsAnyFunctionType) {
-                    return undefined;
-                }
+            if (getObjectFlags(source) & ObjectFlags.NonInferrableType || getPropertiesOfType(source).length === 0 && !getIndexInfoOfType(source, IndexKind.String)) {
+                return undefined;
             }
             // For arrays and tuples we infer new arrays and tuples where the reverse mapping has been
             // applied to the element type(s).
@@ -14619,7 +14609,7 @@ namespace ts {
                     // not contain anyFunctionType when we come back to this argument for its second round
                     // of inference. Also, we exclude inferences for silentNeverType (which is used as a wildcard
                     // when constructing types from type parameters that had no inference candidates).
-                    if (getObjectFlags(source) & ObjectFlags.ContainsAnyFunctionType || source === silentNeverType || (priority & InferencePriority.ReturnType && (source === autoType || source === autoArrayType))) {
+                    if (getObjectFlags(source) & ObjectFlags.NonInferrableType || source === silentNeverType || (priority & InferencePriority.ReturnType && (source === autoType || source === autoArrayType))) {
                         return;
                     }
                     const inference = getInferenceInfoForType(target);
@@ -14932,7 +14922,7 @@ namespace ts {
                 const sourceLen = sourceSignatures.length;
                 const targetLen = targetSignatures.length;
                 const len = sourceLen < targetLen ? sourceLen : targetLen;
-                const skipParameters = !!(getObjectFlags(source) & ObjectFlags.ContainsAnyFunctionType);
+                const skipParameters = !!(getObjectFlags(source) & ObjectFlags.NonInferrableType);
                 for (let i = 0; i < len; i++) {
                     inferFromSignature(getBaseSignature(sourceSignatures[sourceLen - len + i]), getBaseSignature(targetSignatures[targetLen - len + i]), skipParameters);
                 }
@@ -21052,7 +21042,7 @@ namespace ts {
             // returns a function type, we choose to defer processing. This narrowly permits function composition
             // operators to flow inferences through return types, but otherwise processes calls right away. We
             // use the resolvingSignature singleton to indicate that we deferred processing. This result will be
-            // propagated out and eventually turned into silentNeverType (a type that is assignable to anything and
+            // propagated out and eventually turned into nonInferrableType (a type that is assignable to anything and
             // from which we never make inferences).
             if (checkMode & CheckMode.SkipGenericFunctions && !node.typeArguments && callSignatures.some(isGenericFunctionReturningFunction)) {
                 skippedGenericFunction(node, checkMode);
@@ -21535,8 +21525,8 @@ namespace ts {
             const signature = getResolvedSignature(node, /*candidatesOutArray*/ undefined, checkMode);
             if (signature === resolvingSignature) {
                 // CheckMode.SkipGenericFunctions is enabled and this is a call to a generic function that
-                // returns a function type. We defer checking and return anyFunctionType.
-                return silentNeverType;
+                // returns a function type. We defer checking and return nonInferrableType.
+                return nonInferrableType;
             }
 
             if (node.expression.kind === SyntaxKind.SuperKeyword) {
@@ -22343,7 +22333,7 @@ namespace ts {
                     const returnType = getReturnTypeFromBody(node, checkMode);
                     const returnOnlySignature = createSignature(undefined, undefined, undefined, emptyArray, returnType, /*resolvedTypePredicate*/ undefined, 0, /*hasRestParameter*/ false, /*hasLiteralTypes*/ false);
                     const returnOnlyType = createAnonymousType(node.symbol, emptySymbols, [returnOnlySignature], emptyArray, undefined, undefined);
-                    returnOnlyType.objectFlags |= ObjectFlags.ContainsAnyFunctionType;
+                    returnOnlyType.objectFlags |= ObjectFlags.NonInferrableType;
                     return links.contextFreeType = returnOnlyType;
                 }
                 return anyFunctionType;

src/compiler/types.ts

@@ -3944,7 +3944,7 @@ namespace ts {
         Instantiable = InstantiableNonPrimitive | InstantiablePrimitive,
         StructuredOrInstantiable = StructuredType | Instantiable,
         /* @internal */
-        ObjectFlagsType = Nullable | Object | Union | Intersection,
+        ObjectFlagsType = Nullable | Never | Object | Union | Intersection,
         // 'Narrowable' types are types where narrowing actually narrows.
         // This *should* be every type other than null, undefined, void, and never
         Narrowable = Any | Unknown | StructuredOrInstantiable | StringLike | NumberLike | BigIntLike | BooleanLike | ESSymbol | UniqueESSymbol | NonPrimitive,
@@ -4064,12 +4064,12 @@ namespace ts {
         /* @internal */
         ContainsObjectLiteral = 1 << 18, // Type is or contains object literal type
         /* @internal */
-        ContainsAnyFunctionType = 1 << 19, // Type is or contains the anyFunctionType
+        NonInferrableType = 1 << 19, // Type is or contains anyFunctionType or silentNeverType
         ClassOrInterface = Class | Interface,
         /* @internal */
         RequiresWidening = ContainsWideningType | ContainsObjectLiteral,
         /* @internal */
-        PropagatingFlags = ContainsWideningType | ContainsObjectLiteral | ContainsAnyFunctionType
+        PropagatingFlags = ContainsWideningType | ContainsObjectLiteral | NonInferrableType
     }
 
     /* @internal */

tests/baselines/reference/genericFunctionInference2.js

@@ -0,0 +1,26 @@
+//// [genericFunctionInference2.ts]
+// Repro from #30685
+
+type Reducer<S> = (state: S) => S;
+declare function combineReducers<S>(reducers: { [K in keyof S]: Reducer<S[K]> }): Reducer<S>;
+
+type MyState = { combined: { foo: number } };
+declare const foo: Reducer<MyState['combined']['foo']>;
+
+const myReducer1: Reducer<MyState> = combineReducers({
+    combined: combineReducers({ foo }),
+});
+
+const myReducer2 = combineReducers({
+    combined: combineReducers({ foo }),
+});
+
+
+//// [genericFunctionInference2.js]
+// Repro from #30685
+var myReducer1 = combineReducers({
+    combined: combineReducers({ foo: foo })
+});
+var myReducer2 = combineReducers({
+    combined: combineReducers({ foo: foo })
+});

tests/baselines/reference/genericFunctionInference2.symbols

@@ -0,0 +1,56 @@
+=== tests/cases/compiler/genericFunctionInference2.ts ===
+// Repro from #30685
+
+type Reducer<S> = (state: S) => S;
+>Reducer : Symbol(Reducer, Decl(genericFunctionInference2.ts, 0, 0))
+>S : Symbol(S, Decl(genericFunctionInference2.ts, 2, 13))
+>state : Symbol(state, Decl(genericFunctionInference2.ts, 2, 19))
+>S : Symbol(S, Decl(genericFunctionInference2.ts, 2, 13))
+>S : Symbol(S, Decl(genericFunctionInference2.ts, 2, 13))
+
+declare function combineReducers<S>(reducers: { [K in keyof S]: Reducer<S[K]> }): Reducer<S>;
+>combineReducers : Symbol(combineReducers, Decl(genericFunctionInference2.ts, 2, 34))
+>S : Symbol(S, Decl(genericFunctionInference2.ts, 3, 33))
+>reducers : Symbol(reducers, Decl(genericFunctionInference2.ts, 3, 36))
+>K : Symbol(K, Decl(genericFunctionInference2.ts, 3, 49))
+>S : Symbol(S, Decl(genericFunctionInference2.ts, 3, 33))
+>Reducer : Symbol(Reducer, Decl(genericFunctionInference2.ts, 0, 0))
+>S : Symbol(S, Decl(genericFunctionInference2.ts, 3, 33))
+>K : Symbol(K, Decl(genericFunctionInference2.ts, 3, 49))
+>Reducer : Symbol(Reducer, Decl(genericFunctionInference2.ts, 0, 0))
+>S : Symbol(S, Decl(genericFunctionInference2.ts, 3, 33))
+
+type MyState = { combined: { foo: number } };
+>MyState : Symbol(MyState, Decl(genericFunctionInference2.ts, 3, 93))
+>combined : Symbol(combined, Decl(genericFunctionInference2.ts, 5, 16))
+>foo : Symbol(foo, Decl(genericFunctionInference2.ts, 5, 28))
+
+declare const foo: Reducer<MyState['combined']['foo']>;
+>foo : Symbol(foo, Decl(genericFunctionInference2.ts, 6, 13))
+>Reducer : Symbol(Reducer, Decl(genericFunctionInference2.ts, 0, 0))
+>MyState : Symbol(MyState, Decl(genericFunctionInference2.ts, 3, 93))
+
+const myReducer1: Reducer<MyState> = combineReducers({
+>myReducer1 : Symbol(myReducer1, Decl(genericFunctionInference2.ts, 8, 5))
+>Reducer : Symbol(Reducer, Decl(genericFunctionInference2.ts, 0, 0))
+>MyState : Symbol(MyState, Decl(genericFunctionInference2.ts, 3, 93))
+>combineReducers : Symbol(combineReducers, Decl(genericFunctionInference2.ts, 2, 34))
+
+    combined: combineReducers({ foo }),
+>combined : Symbol(combined, Decl(genericFunctionInference2.ts, 8, 54))
+>combineReducers : Symbol(combineReducers, Decl(genericFunctionInference2.ts, 2, 34))
+>foo : Symbol(foo, Decl(genericFunctionInference2.ts, 9, 31))
+
+});
+
+const myReducer2 = combineReducers({
+>myReducer2 : Symbol(myReducer2, Decl(genericFunctionInference2.ts, 12, 5))
+>combineReducers : Symbol(combineReducers, Decl(genericFunctionInference2.ts, 2, 34))
+
+    combined: combineReducers({ foo }),
+>combined : Symbol(combined, Decl(genericFunctionInference2.ts, 12, 36))
+>combineReducers : Symbol(combineReducers, Decl(genericFunctionInference2.ts, 2, 34))
+>foo : Symbol(foo, Decl(genericFunctionInference2.ts, 13, 31))
+
+});
+

tests/baselines/reference/genericFunctionInference2.types

@@ -0,0 +1,49 @@
+=== tests/cases/compiler/genericFunctionInference2.ts ===
+// Repro from #30685
+
+type Reducer<S> = (state: S) => S;
+>Reducer : Reducer<S>
+>state : S
+
+declare function combineReducers<S>(reducers: { [K in keyof S]: Reducer<S[K]> }): Reducer<S>;
+>combineReducers : <S>(reducers: { [K in keyof S]: Reducer<S[K]>; }) => Reducer<S>
+>reducers : { [K in keyof S]: Reducer<S[K]>; }
+
+type MyState = { combined: { foo: number } };
+>MyState : MyState
+>combined : { foo: number; }
+>foo : number
+
+declare const foo: Reducer<MyState['combined']['foo']>;
+>foo : Reducer<number>
+
+const myReducer1: Reducer<MyState> = combineReducers({
+>myReducer1 : Reducer<MyState>
+>combineReducers({    combined: combineReducers({ foo }),}) : Reducer<{ combined: { foo: any; }; }>
+>combineReducers : <S>(reducers: { [K in keyof S]: Reducer<S[K]>; }) => Reducer<S>
+>{    combined: combineReducers({ foo }),} : { combined: Reducer<{ foo: number; }>; }
+
+    combined: combineReducers({ foo }),
+>combined : Reducer<{ foo: number; }>
+>combineReducers({ foo }) : Reducer<{ foo: number; }>
+>combineReducers : <S>(reducers: { [K in keyof S]: Reducer<S[K]>; }) => Reducer<S>
+>{ foo } : { foo: Reducer<number>; }
+>foo : Reducer<number>
+
+});
+
+const myReducer2 = combineReducers({
+>myReducer2 : Reducer<{ combined: { foo: any; }; }>
+>combineReducers({    combined: combineReducers({ foo }),}) : Reducer<{ combined: { foo: any; }; }>
+>combineReducers : <S>(reducers: { [K in keyof S]: Reducer<S[K]>; }) => Reducer<S>
+>{    combined: combineReducers({ foo }),} : { combined: Reducer<{ foo: number; }>; }
+
+    combined: combineReducers({ foo }),
+>combined : Reducer<{ foo: number; }>
+>combineReducers({ foo }) : Reducer<{ foo: number; }>
+>combineReducers : <S>(reducers: { [K in keyof S]: Reducer<S[K]>; }) => Reducer<S>
+>{ foo } : { foo: Reducer<number>; }
+>foo : Reducer<number>
+
+});
+

tests/cases/compiler/genericFunctionInference2.ts

@@ -0,0 +1,15 @@
+// Repro from #30685
+
+type Reducer<S> = (state: S) => S;
+declare function combineReducers<S>(reducers: { [K in keyof S]: Reducer<S[K]> }): Reducer<S>;
+
+type MyState = { combined: { foo: number } };
+declare const foo: Reducer<MyState['combined']['foo']>;
+
+const myReducer1: Reducer<MyState> = combineReducers({
+    combined: combineReducers({ foo }),
+});
+
+const myReducer2 = combineReducers({
+    combined: combineReducers({ foo }),
+});