Track recursive homomorphic mapped types by the symbol of their target (

#55638)
microsoft · Sep 11, 2023 · 4f899a1 · 4f899a1
1 parent eb2d1f9
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diff --git a/src/compiler/checker.ts b/src/compiler/checker.ts
@@ -23484,10 +23484,18 @@ export function createTypeChecker(host: TypeCheckerHost): TypeChecker {
                 // unique AST node.
                 return (type as TypeReference).node!;
             }
-            if (type.symbol && !(getObjectFlags(type) & ObjectFlags.Anonymous && type.symbol.flags & SymbolFlags.Class)) {
-                // We track all object types that have an associated symbol (representing the origin of the type), but
-                // exclude the static side of classes from this check since it shares its symbol with the instance side.
-                return type.symbol;
+            if (type.symbol) {
+                // We track object types that have a symbol by that symbol (representing the origin of the type).
+                if (getObjectFlags(type) & ObjectFlags.Mapped) {
+                    // When a homomorphic mapped type is applied to a type with a symbol, we use the symbol of that
+                    // type as the recursion identity. This is a better strategy than using the symbol of the mapped
+                    // type, which doesn't work well for recursive mapped types.
+                    type = getMappedTargetWithSymbol(type);
+                }
+                if (!(getObjectFlags(type) & ObjectFlags.Anonymous && type.symbol.flags & SymbolFlags.Class)) {
+                    // We exclude the static side of a class since it shares its symbol with the instance side.
+                    return type.symbol;
+                }
             }
             if (isTupleType(type)) {
                 return type.target;
@@ -23511,6 +23519,14 @@ export function createTypeChecker(host: TypeCheckerHost): TypeChecker {
         return type;
     }
 
+    function getMappedTargetWithSymbol(type: Type) {
+        let target = type;
+        while ((getObjectFlags(target) & ObjectFlags.InstantiatedMapped) === ObjectFlags.InstantiatedMapped && isMappedTypeWithKeyofConstraintDeclaration(target as MappedType)) {
+            target = getModifiersTypeFromMappedType(target as MappedType);
+        }
+        return target.symbol ? target : type;
+    }
+
     function isPropertyIdenticalTo(sourceProp: Symbol, targetProp: Symbol): boolean {
         return compareProperties(sourceProp, targetProp, compareTypesIdentical) !== Ternary.False;
     }

diff --git a/src/compiler/types.ts b/src/compiler/types.ts
@@ -6204,6 +6204,8 @@ export const enum ObjectFlags {
     RequiresWidening = ContainsWideningType | ContainsObjectOrArrayLiteral,
     /** @internal */
     PropagatingFlags = ContainsWideningType | ContainsObjectOrArrayLiteral | NonInferrableType,
+    /** @internal */
+    InstantiatedMapped = Mapped | Instantiated,
     // Object flags that uniquely identify the kind of ObjectType
     /** @internal */
     ObjectTypeKindMask = ClassOrInterface | Reference | Tuple | Anonymous | Mapped | ReverseMapped | EvolvingArray,

diff --git a/tests/baselines/reference/deeplyNestedMappedTypes.errors.txt b/tests/baselines/reference/deeplyNestedMappedTypes.errors.txt
@@ -0,0 +1,63 @@
+deeplyNestedMappedTypes.ts(9,7): error TS2322: Type 'Id<{ x: { y: { z: { a: { b: { c: number; }; }; }; }; }; }>' is not assignable to type 'Id<{ x: { y: { z: { a: { b: { c: string; }; }; }; }; }; }>'.
+  The types of 'x.y.z.a.b.c' are incompatible between these types.
+    Type 'number' is not assignable to type 'string'.
+deeplyNestedMappedTypes.ts(17,7): error TS2322: Type 'Id2<{ x: { y: { z: { a: { b: { c: number; }; }; }; }; }; }>' is not assignable to type 'Id2<{ x: { y: { z: { a: { b: { c: string; }; }; }; }; }; }>'.
+  The types of 'x.y.z.a.b.c' are incompatible between these types.
+    Type 'number' is not assignable to type 'string'.
+
+
+==== deeplyNestedMappedTypes.ts (2 errors) ====
+    // Simplified repro from #55535
+
+    type Id<T> = { [K in keyof T]: Id<T[K]> };
+
+    type Foo1 = Id<{ x: { y: { z: { a: { b: { c: number } } } } } }>;
+    type Foo2 = Id<{ x: { y: { z: { a: { b: { c: string } } } } } }>;
+
+    declare const foo1: Foo1;
+    const foo2: Foo2 = foo1;  // Error expected
+          ~~~~
+!!! error TS2322: Type 'Id<{ x: { y: { z: { a: { b: { c: number; }; }; }; }; }; }>' is not assignable to type 'Id<{ x: { y: { z: { a: { b: { c: string; }; }; }; }; }; }>'.
+!!! error TS2322:   The types of 'x.y.z.a.b.c' are incompatible between these types.
+!!! error TS2322:     Type 'number' is not assignable to type 'string'.
+
+    type Id2<T> = { [K in keyof T]: Id2<Id2<T[K]>> };
+
+    type Foo3 = Id2<{ x: { y: { z: { a: { b: { c: number } } } } } }>;
+    type Foo4 = Id2<{ x: { y: { z: { a: { b: { c: string } } } } } }>;
+
+    declare const foo3: Foo3;
+    const foo4: Foo4 = foo3;  // Error expected
+          ~~~~
+!!! error TS2322: Type 'Id2<{ x: { y: { z: { a: { b: { c: number; }; }; }; }; }; }>' is not assignable to type 'Id2<{ x: { y: { z: { a: { b: { c: string; }; }; }; }; }; }>'.
+!!! error TS2322:   The types of 'x.y.z.a.b.c' are incompatible between these types.
+!!! error TS2322:     Type 'number' is not assignable to type 'string'.
+
+    // Repro from issue linked in #55535
+
+    type RequiredDeep<T> = { [K in keyof T]-?: RequiredDeep<T[K]> };
+
+    type A = { a?: { b: { c: 1 | { d: 2000 } }}}
+    type B = { a?: { b: { c: { d: { e: { f: { g: 2 }}}}, x: 1000 }}}
+
+    type C = RequiredDeep<A>;
+    type D = RequiredDeep<B>;
+
+    type Test1 = [C, D] extends [D, C] ? true : false;  // false
+    type Test2 = C extends D ? true : false;  // false
+    type Test3 = D extends C ? true : false;  // false
+
+    // Simplified repro from #54246
+
+    // Except for the final non-recursive Record<K, V>, object types produced by NestedRecord all have the same symbol
+    // and thus are considered deeply nested after three levels of nesting. Ideally we'd detect that recursion in this
+    // type always terminates, but we're unaware of a general algorithm that accomplishes this.
+
+    type NestedRecord<K extends string, V> = K extends `${infer K0}.${infer KR}` ? { [P in K0]: NestedRecord<KR, V> } : Record<K, V>;
+
+    type Bar1 = NestedRecord<"x.y.z.a.b.c", number>;
+    type Bar2 = NestedRecord<"x.y.z.a.b.c", string>;
+
+    declare const bar1: Bar1;
+    const bar2: Bar2 = bar1;  // Error expected
+
diff --git a/tests/baselines/reference/deeplyNestedMappedTypes.symbols b/tests/baselines/reference/deeplyNestedMappedTypes.symbols
@@ -0,0 +1,177 @@
+//// [tests/cases/compiler/deeplyNestedMappedTypes.ts] ////
+
+=== deeplyNestedMappedTypes.ts ===
+// Simplified repro from #55535
+
+type Id<T> = { [K in keyof T]: Id<T[K]> };
+>Id : Symbol(Id, Decl(deeplyNestedMappedTypes.ts, 0, 0))
+>T : Symbol(T, Decl(deeplyNestedMappedTypes.ts, 2, 8))
+>K : Symbol(K, Decl(deeplyNestedMappedTypes.ts, 2, 16))
+>T : Symbol(T, Decl(deeplyNestedMappedTypes.ts, 2, 8))
+>Id : Symbol(Id, Decl(deeplyNestedMappedTypes.ts, 0, 0))
+>T : Symbol(T, Decl(deeplyNestedMappedTypes.ts, 2, 8))
+>K : Symbol(K, Decl(deeplyNestedMappedTypes.ts, 2, 16))
+
+type Foo1 = Id<{ x: { y: { z: { a: { b: { c: number } } } } } }>;
+>Foo1 : Symbol(Foo1, Decl(deeplyNestedMappedTypes.ts, 2, 42))
+>Id : Symbol(Id, Decl(deeplyNestedMappedTypes.ts, 0, 0))
+>x : Symbol(x, Decl(deeplyNestedMappedTypes.ts, 4, 16))
+>y : Symbol(y, Decl(deeplyNestedMappedTypes.ts, 4, 21))
+>z : Symbol(z, Decl(deeplyNestedMappedTypes.ts, 4, 26))
+>a : Symbol(a, Decl(deeplyNestedMappedTypes.ts, 4, 31))
+>b : Symbol(b, Decl(deeplyNestedMappedTypes.ts, 4, 36))
+>c : Symbol(c, Decl(deeplyNestedMappedTypes.ts, 4, 41))
+
+type Foo2 = Id<{ x: { y: { z: { a: { b: { c: string } } } } } }>;
+>Foo2 : Symbol(Foo2, Decl(deeplyNestedMappedTypes.ts, 4, 65))
+>Id : Symbol(Id, Decl(deeplyNestedMappedTypes.ts, 0, 0))
+>x : Symbol(x, Decl(deeplyNestedMappedTypes.ts, 5, 16))
+>y : Symbol(y, Decl(deeplyNestedMappedTypes.ts, 5, 21))
+>z : Symbol(z, Decl(deeplyNestedMappedTypes.ts, 5, 26))
+>a : Symbol(a, Decl(deeplyNestedMappedTypes.ts, 5, 31))
+>b : Symbol(b, Decl(deeplyNestedMappedTypes.ts, 5, 36))
+>c : Symbol(c, Decl(deeplyNestedMappedTypes.ts, 5, 41))
+
+declare const foo1: Foo1;
+>foo1 : Symbol(foo1, Decl(deeplyNestedMappedTypes.ts, 7, 13))
+>Foo1 : Symbol(Foo1, Decl(deeplyNestedMappedTypes.ts, 2, 42))
+
+const foo2: Foo2 = foo1;  // Error expected
+>foo2 : Symbol(foo2, Decl(deeplyNestedMappedTypes.ts, 8, 5))
+>Foo2 : Symbol(Foo2, Decl(deeplyNestedMappedTypes.ts, 4, 65))
+>foo1 : Symbol(foo1, Decl(deeplyNestedMappedTypes.ts, 7, 13))
+
+type Id2<T> = { [K in keyof T]: Id2<Id2<T[K]>> };
+>Id2 : Symbol(Id2, Decl(deeplyNestedMappedTypes.ts, 8, 24))
+>T : Symbol(T, Decl(deeplyNestedMappedTypes.ts, 10, 9))
+>K : Symbol(K, Decl(deeplyNestedMappedTypes.ts, 10, 17))
+>T : Symbol(T, Decl(deeplyNestedMappedTypes.ts, 10, 9))
+>Id2 : Symbol(Id2, Decl(deeplyNestedMappedTypes.ts, 8, 24))
+>Id2 : Symbol(Id2, Decl(deeplyNestedMappedTypes.ts, 8, 24))
+>T : Symbol(T, Decl(deeplyNestedMappedTypes.ts, 10, 9))
+>K : Symbol(K, Decl(deeplyNestedMappedTypes.ts, 10, 17))
+
+type Foo3 = Id2<{ x: { y: { z: { a: { b: { c: number } } } } } }>;
+>Foo3 : Symbol(Foo3, Decl(deeplyNestedMappedTypes.ts, 10, 49))
+>Id2 : Symbol(Id2, Decl(deeplyNestedMappedTypes.ts, 8, 24))
+>x : Symbol(x, Decl(deeplyNestedMappedTypes.ts, 12, 17))
+>y : Symbol(y, Decl(deeplyNestedMappedTypes.ts, 12, 22))
+>z : Symbol(z, Decl(deeplyNestedMappedTypes.ts, 12, 27))
+>a : Symbol(a, Decl(deeplyNestedMappedTypes.ts, 12, 32))
+>b : Symbol(b, Decl(deeplyNestedMappedTypes.ts, 12, 37))
+>c : Symbol(c, Decl(deeplyNestedMappedTypes.ts, 12, 42))
+
+type Foo4 = Id2<{ x: { y: { z: { a: { b: { c: string } } } } } }>;
+>Foo4 : Symbol(Foo4, Decl(deeplyNestedMappedTypes.ts, 12, 66))
+>Id2 : Symbol(Id2, Decl(deeplyNestedMappedTypes.ts, 8, 24))
+>x : Symbol(x, Decl(deeplyNestedMappedTypes.ts, 13, 17))
+>y : Symbol(y, Decl(deeplyNestedMappedTypes.ts, 13, 22))
+>z : Symbol(z, Decl(deeplyNestedMappedTypes.ts, 13, 27))
+>a : Symbol(a, Decl(deeplyNestedMappedTypes.ts, 13, 32))
+>b : Symbol(b, Decl(deeplyNestedMappedTypes.ts, 13, 37))
+>c : Symbol(c, Decl(deeplyNestedMappedTypes.ts, 13, 42))
+
+declare const foo3: Foo3;
+>foo3 : Symbol(foo3, Decl(deeplyNestedMappedTypes.ts, 15, 13))
+>Foo3 : Symbol(Foo3, Decl(deeplyNestedMappedTypes.ts, 10, 49))
+
+const foo4: Foo4 = foo3;  // Error expected
+>foo4 : Symbol(foo4, Decl(deeplyNestedMappedTypes.ts, 16, 5))
+>Foo4 : Symbol(Foo4, Decl(deeplyNestedMappedTypes.ts, 12, 66))
+>foo3 : Symbol(foo3, Decl(deeplyNestedMappedTypes.ts, 15, 13))
+
+// Repro from issue linked in #55535
+
+type RequiredDeep<T> = { [K in keyof T]-?: RequiredDeep<T[K]> };
+>RequiredDeep : Symbol(RequiredDeep, Decl(deeplyNestedMappedTypes.ts, 16, 24))
+>T : Symbol(T, Decl(deeplyNestedMappedTypes.ts, 20, 18))
+>K : Symbol(K, Decl(deeplyNestedMappedTypes.ts, 20, 26))
+>T : Symbol(T, Decl(deeplyNestedMappedTypes.ts, 20, 18))
+>RequiredDeep : Symbol(RequiredDeep, Decl(deeplyNestedMappedTypes.ts, 16, 24))
+>T : Symbol(T, Decl(deeplyNestedMappedTypes.ts, 20, 18))
+>K : Symbol(K, Decl(deeplyNestedMappedTypes.ts, 20, 26))
+
+type A = { a?: { b: { c: 1 | { d: 2000 } }}}
+>A : Symbol(A, Decl(deeplyNestedMappedTypes.ts, 20, 64))
+>a : Symbol(a, Decl(deeplyNestedMappedTypes.ts, 22, 10))
+>b : Symbol(b, Decl(deeplyNestedMappedTypes.ts, 22, 16))
+>c : Symbol(c, Decl(deeplyNestedMappedTypes.ts, 22, 21))
+>d : Symbol(d, Decl(deeplyNestedMappedTypes.ts, 22, 30))
+
+type B = { a?: { b: { c: { d: { e: { f: { g: 2 }}}}, x: 1000 }}}
+>B : Symbol(B, Decl(deeplyNestedMappedTypes.ts, 22, 44))
+>a : Symbol(a, Decl(deeplyNestedMappedTypes.ts, 23, 10))
+>b : Symbol(b, Decl(deeplyNestedMappedTypes.ts, 23, 16))
+>c : Symbol(c, Decl(deeplyNestedMappedTypes.ts, 23, 21))
+>d : Symbol(d, Decl(deeplyNestedMappedTypes.ts, 23, 26))
+>e : Symbol(e, Decl(deeplyNestedMappedTypes.ts, 23, 31))
+>f : Symbol(f, Decl(deeplyNestedMappedTypes.ts, 23, 36))
+>g : Symbol(g, Decl(deeplyNestedMappedTypes.ts, 23, 41))
+>x : Symbol(x, Decl(deeplyNestedMappedTypes.ts, 23, 52))
+
+type C = RequiredDeep<A>;
+>C : Symbol(C, Decl(deeplyNestedMappedTypes.ts, 23, 64))
+>RequiredDeep : Symbol(RequiredDeep, Decl(deeplyNestedMappedTypes.ts, 16, 24))
+>A : Symbol(A, Decl(deeplyNestedMappedTypes.ts, 20, 64))
+
+type D = RequiredDeep<B>;
+>D : Symbol(D, Decl(deeplyNestedMappedTypes.ts, 25, 25))
+>RequiredDeep : Symbol(RequiredDeep, Decl(deeplyNestedMappedTypes.ts, 16, 24))
+>B : Symbol(B, Decl(deeplyNestedMappedTypes.ts, 22, 44))
+
+type Test1 = [C, D] extends [D, C] ? true : false;  // false
+>Test1 : Symbol(Test1, Decl(deeplyNestedMappedTypes.ts, 26, 25))
+>C : Symbol(C, Decl(deeplyNestedMappedTypes.ts, 23, 64))
+>D : Symbol(D, Decl(deeplyNestedMappedTypes.ts, 25, 25))
+>D : Symbol(D, Decl(deeplyNestedMappedTypes.ts, 25, 25))
+>C : Symbol(C, Decl(deeplyNestedMappedTypes.ts, 23, 64))
+
+type Test2 = C extends D ? true : false;  // false
+>Test2 : Symbol(Test2, Decl(deeplyNestedMappedTypes.ts, 28, 50))
+>C : Symbol(C, Decl(deeplyNestedMappedTypes.ts, 23, 64))
+>D : Symbol(D, Decl(deeplyNestedMappedTypes.ts, 25, 25))
+
+type Test3 = D extends C ? true : false;  // false
+>Test3 : Symbol(Test3, Decl(deeplyNestedMappedTypes.ts, 29, 40))
+>D : Symbol(D, Decl(deeplyNestedMappedTypes.ts, 25, 25))
+>C : Symbol(C, Decl(deeplyNestedMappedTypes.ts, 23, 64))
+
+// Simplified repro from #54246
+
+// Except for the final non-recursive Record<K, V>, object types produced by NestedRecord all have the same symbol
+// and thus are considered deeply nested after three levels of nesting. Ideally we'd detect that recursion in this
+// type always terminates, but we're unaware of a general algorithm that accomplishes this.
+
+type NestedRecord<K extends string, V> = K extends `${infer K0}.${infer KR}` ? { [P in K0]: NestedRecord<KR, V> } : Record<K, V>;
+>NestedRecord : Symbol(NestedRecord, Decl(deeplyNestedMappedTypes.ts, 30, 40))
+>K : Symbol(K, Decl(deeplyNestedMappedTypes.ts, 38, 18))
+>V : Symbol(V, Decl(deeplyNestedMappedTypes.ts, 38, 35))
+>K : Symbol(K, Decl(deeplyNestedMappedTypes.ts, 38, 18))
+>K0 : Symbol(K0, Decl(deeplyNestedMappedTypes.ts, 38, 59))
+>KR : Symbol(KR, Decl(deeplyNestedMappedTypes.ts, 38, 71))
+>P : Symbol(P, Decl(deeplyNestedMappedTypes.ts, 38, 82))
+>K0 : Symbol(K0, Decl(deeplyNestedMappedTypes.ts, 38, 59))
+>NestedRecord : Symbol(NestedRecord, Decl(deeplyNestedMappedTypes.ts, 30, 40))
+>KR : Symbol(KR, Decl(deeplyNestedMappedTypes.ts, 38, 71))
+>V : Symbol(V, Decl(deeplyNestedMappedTypes.ts, 38, 35))
+>Record : Symbol(Record, Decl(lib.es5.d.ts, --, --))
+>K : Symbol(K, Decl(deeplyNestedMappedTypes.ts, 38, 18))
+>V : Symbol(V, Decl(deeplyNestedMappedTypes.ts, 38, 35))
+
+type Bar1 = NestedRecord<"x.y.z.a.b.c", number>;
+>Bar1 : Symbol(Bar1, Decl(deeplyNestedMappedTypes.ts, 38, 129))
+>NestedRecord : Symbol(NestedRecord, Decl(deeplyNestedMappedTypes.ts, 30, 40))
+
+type Bar2 = NestedRecord<"x.y.z.a.b.c", string>;
+>Bar2 : Symbol(Bar2, Decl(deeplyNestedMappedTypes.ts, 40, 48))
+>NestedRecord : Symbol(NestedRecord, Decl(deeplyNestedMappedTypes.ts, 30, 40))
+
+declare const bar1: Bar1;
+>bar1 : Symbol(bar1, Decl(deeplyNestedMappedTypes.ts, 43, 13))
+>Bar1 : Symbol(Bar1, Decl(deeplyNestedMappedTypes.ts, 38, 129))
+
+const bar2: Bar2 = bar1;  // Error expected
+>bar2 : Symbol(bar2, Decl(deeplyNestedMappedTypes.ts, 44, 5))
+>Bar2 : Symbol(Bar2, Decl(deeplyNestedMappedTypes.ts, 40, 48))
+>bar1 : Symbol(bar1, Decl(deeplyNestedMappedTypes.ts, 43, 13))
+