Port missing keyof simplification for generic mapped types with name types

tsc/internal/checker/checker.go

@@ -8427,16 +8427,9 @@ func (c *Checker) checkIndexedAccessIndexType(t *Type, accessNode *ast.Node) *Ty
 	// Check if the index type is assignable to 'keyof T' for the object type.
 	objectType := t.AsIndexedAccessType().objectType
 	indexType := t.AsIndexedAccessType().indexType
-	// skip index type deferral on remapping mapped types
-	var objectIndexType *Type
-	if c.isGenericMappedType(objectType) && c.getMappedTypeNameTypeKind(objectType) == MappedTypeNameTypeKindRemapping {
-		objectIndexType = c.getIndexTypeForMappedType(objectType, IndexFlagsNone)
-	} else {
-		objectIndexType = c.getIndexTypeEx(objectType, IndexFlagsNone)
-	}
 	hasNumberIndexInfo := c.getIndexInfoOfType(objectType, c.numberType) != nil
 	if everyType(indexType, func(t *Type) bool {
-		return c.isTypeAssignableTo(t, objectIndexType) || hasNumberIndexInfo && c.isApplicableIndexType(t, c.numberType)
+		return c.isTypeAssignableTo(t, c.getIndexTypeEx(objectType, IndexFlagsNone)) || hasNumberIndexInfo && c.isApplicableIndexType(t, c.numberType)
 	}) {
 		if accessNode.Kind == ast.KindElementAccessExpression && ast.IsAssignmentTarget(accessNode) && objectType.objectFlags&ObjectFlagsMapped != 0 && getMappedTypeModifiers(objectType)&MappedTypeModifiersIncludeReadonly != 0 {
 			c.error(accessNode, diagnostics.Index_signature_in_type_0_only_permits_reading, c.TypeToString(objectType))
@@ -28444,6 +28437,16 @@ func (c *Checker) getSimplifiedType(t *Type, writing bool) *Type {
 		return c.getSimplifiedIndexedAccessType(t, writing)
 	case t.flags&TypeFlagsConditional != 0:
 		return c.getSimplifiedConditionalType(t, writing)
+	case t.flags&TypeFlagsIndex != 0:
+		return c.getSimplifiedIndexType(t)
+	}
+	return t
+}
+
+func (c *Checker) getSimplifiedIndexType(t *Type) *Type {
+	target := t.AsIndexType().target
+	if c.isGenericMappedType(target) && c.getNameTypeFromMappedType(target) != nil && !c.isMappedTypeWithKeyofConstraintDeclaration(target) {
+		return c.getIndexTypeForMappedType(target, IndexFlagsNone)
 	}
 	return t
 }

tsc/testdata/baselines/reference/compiler/mappedTypeAsClauseIntersectionConstraintIndexedAccess.symbols

@@ -0,0 +1,71 @@
+//// [tests/cases/compiler/mappedTypeAsClauseIntersectionConstraintIndexedAccess.ts] ////
+
+=== mappedTypeAsClauseIntersectionConstraintIndexedAccess.ts ===
+type ChildPaths<T> = [PathTuples<T>] extends [never] ? [] : PathTuples<T>;
+>ChildPaths : Symbol(ChildPaths, Decl(mappedTypeAsClauseIntersectionConstraintIndexedAccess.ts, 0, 0))
+>T : Symbol(T, Decl(mappedTypeAsClauseIntersectionConstraintIndexedAccess.ts, 0, 16))
+>PathTuples : Symbol(PathTuples, Decl(mappedTypeAsClauseIntersectionConstraintIndexedAccess.ts, 0, 74))
+>T : Symbol(T, Decl(mappedTypeAsClauseIntersectionConstraintIndexedAccess.ts, 0, 16))
+>PathTuples : Symbol(PathTuples, Decl(mappedTypeAsClauseIntersectionConstraintIndexedAccess.ts, 0, 74))
+>T : Symbol(T, Decl(mappedTypeAsClauseIntersectionConstraintIndexedAccess.ts, 0, 16))
+
+type PathTuples<T> = T extends object
+>PathTuples : Symbol(PathTuples, Decl(mappedTypeAsClauseIntersectionConstraintIndexedAccess.ts, 0, 74))
+>T : Symbol(T, Decl(mappedTypeAsClauseIntersectionConstraintIndexedAccess.ts, 1, 16))
+>T : Symbol(T, Decl(mappedTypeAsClauseIntersectionConstraintIndexedAccess.ts, 1, 16))
+
+  ? {
+      [K in keyof T & string as K extends '_key' ? never : K]: [PathTuples<T[K]>] extends [never]
+>K : Symbol(K, Decl(mappedTypeAsClauseIntersectionConstraintIndexedAccess.ts, 3, 7))
+>T : Symbol(T, Decl(mappedTypeAsClauseIntersectionConstraintIndexedAccess.ts, 1, 16))
+>K : Symbol(K, Decl(mappedTypeAsClauseIntersectionConstraintIndexedAccess.ts, 3, 7))
+>K : Symbol(K, Decl(mappedTypeAsClauseIntersectionConstraintIndexedAccess.ts, 3, 7))
+>PathTuples : Symbol(PathTuples, Decl(mappedTypeAsClauseIntersectionConstraintIndexedAccess.ts, 0, 74))
+>T : Symbol(T, Decl(mappedTypeAsClauseIntersectionConstraintIndexedAccess.ts, 1, 16))
+>K : Symbol(K, Decl(mappedTypeAsClauseIntersectionConstraintIndexedAccess.ts, 3, 7))
+
+        ? never
+        : readonly [K, ...ChildPaths<T[K]>];
+>K : Symbol(K, Decl(mappedTypeAsClauseIntersectionConstraintIndexedAccess.ts, 3, 7))
+>ChildPaths : Symbol(ChildPaths, Decl(mappedTypeAsClauseIntersectionConstraintIndexedAccess.ts, 0, 0))
+>T : Symbol(T, Decl(mappedTypeAsClauseIntersectionConstraintIndexedAccess.ts, 1, 16))
+>K : Symbol(K, Decl(mappedTypeAsClauseIntersectionConstraintIndexedAccess.ts, 3, 7))
+
+    }[Exclude<keyof T & string, '_key'>]
+>Exclude : Symbol(Exclude, Decl(lib.es5.d.ts, --, --))
+>T : Symbol(T, Decl(mappedTypeAsClauseIntersectionConstraintIndexedAccess.ts, 1, 16))
+
+  : [];
+
+type T1 = PathTuples<{ a: string; _key: string; b: { c: number } }>;
+>T1 : Symbol(T1, Decl(mappedTypeAsClauseIntersectionConstraintIndexedAccess.ts, 7, 7))
+>PathTuples : Symbol(PathTuples, Decl(mappedTypeAsClauseIntersectionConstraintIndexedAccess.ts, 0, 74))
+>a : Symbol(a, Decl(mappedTypeAsClauseIntersectionConstraintIndexedAccess.ts, 9, 22))
+>_key : Symbol(_key, Decl(mappedTypeAsClauseIntersectionConstraintIndexedAccess.ts, 9, 33))
+>b : Symbol(b, Decl(mappedTypeAsClauseIntersectionConstraintIndexedAccess.ts, 9, 47))
+>c : Symbol(c, Decl(mappedTypeAsClauseIntersectionConstraintIndexedAccess.ts, 9, 52))
+
+const t1: T1 = ['b', 'c'];
+>t1 : Symbol(t1, Decl(mappedTypeAsClauseIntersectionConstraintIndexedAccess.ts, 10, 5))
+>T1 : Symbol(T1, Decl(mappedTypeAsClauseIntersectionConstraintIndexedAccess.ts, 7, 7))
+
+type S1<T> = { [K in keyof T & string as K extends '_key' ? never : K]: 1 }[Exclude<keyof T & string, '_key'>];
+>S1 : Symbol(S1, Decl(mappedTypeAsClauseIntersectionConstraintIndexedAccess.ts, 10, 26))
+>T : Symbol(T, Decl(mappedTypeAsClauseIntersectionConstraintIndexedAccess.ts, 12, 8))
+>K : Symbol(K, Decl(mappedTypeAsClauseIntersectionConstraintIndexedAccess.ts, 12, 16))
+>T : Symbol(T, Decl(mappedTypeAsClauseIntersectionConstraintIndexedAccess.ts, 12, 8))
+>K : Symbol(K, Decl(mappedTypeAsClauseIntersectionConstraintIndexedAccess.ts, 12, 16))
+>K : Symbol(K, Decl(mappedTypeAsClauseIntersectionConstraintIndexedAccess.ts, 12, 16))
+>Exclude : Symbol(Exclude, Decl(lib.es5.d.ts, --, --))
+>T : Symbol(T, Decl(mappedTypeAsClauseIntersectionConstraintIndexedAccess.ts, 12, 8))
+
+type S2<T> = { [K in string & keyof T as K extends '_key' ? never : K]: 1 }[Exclude<string & keyof T, '_key'>];
+>S2 : Symbol(S2, Decl(mappedTypeAsClauseIntersectionConstraintIndexedAccess.ts, 12, 111))
+>T : Symbol(T, Decl(mappedTypeAsClauseIntersectionConstraintIndexedAccess.ts, 13, 8))
+>K : Symbol(K, Decl(mappedTypeAsClauseIntersectionConstraintIndexedAccess.ts, 13, 16))
+>T : Symbol(T, Decl(mappedTypeAsClauseIntersectionConstraintIndexedAccess.ts, 13, 8))
+>K : Symbol(K, Decl(mappedTypeAsClauseIntersectionConstraintIndexedAccess.ts, 13, 16))
+>K : Symbol(K, Decl(mappedTypeAsClauseIntersectionConstraintIndexedAccess.ts, 13, 16))
+>Exclude : Symbol(Exclude, Decl(lib.es5.d.ts, --, --))
+>T : Symbol(T, Decl(mappedTypeAsClauseIntersectionConstraintIndexedAccess.ts, 13, 8))
+

tsc/testdata/baselines/reference/compiler/mappedTypeAsClauseIntersectionConstraintIndexedAccess.types

@@ -0,0 +1,35 @@
+//// [tests/cases/compiler/mappedTypeAsClauseIntersectionConstraintIndexedAccess.ts] ////
+
+=== mappedTypeAsClauseIntersectionConstraintIndexedAccess.ts ===
+type ChildPaths<T> = [PathTuples<T>] extends [never] ? [] : PathTuples<T>;
+>ChildPaths : ChildPaths<T>
+
+type PathTuples<T> = T extends object
+>PathTuples : PathTuples<T>
+
+  ? {
+      [K in keyof T & string as K extends '_key' ? never : K]: [PathTuples<T[K]>] extends [never]
+        ? never
+        : readonly [K, ...ChildPaths<T[K]>];
+    }[Exclude<keyof T & string, '_key'>]
+  : [];
+
+type T1 = PathTuples<{ a: string; _key: string; b: { c: number } }>;
+>T1 : readonly ["a"] | readonly ["b", "c"]
+>a : string
+>_key : string
+>b : { c: number; }
+>c : number
+
+const t1: T1 = ['b', 'c'];
+>t1 : readonly ["a"] | readonly ["b", "c"]
+>['b', 'c'] : ["b", "c"]
+>'b' : "b"
+>'c' : "c"
+
+type S1<T> = { [K in keyof T & string as K extends '_key' ? never : K]: 1 }[Exclude<keyof T & string, '_key'>];
+>S1 : S1<T>
+
+type S2<T> = { [K in string & keyof T as K extends '_key' ? never : K]: 1 }[Exclude<string & keyof T, '_key'>];
+>S2 : S2<T>
+

tsc/testdata/baselines/reference/conformance/mappedTypeConstraints2.errors.txt

@@ -4,7 +4,8 @@ mappedTypeConstraints2.ts(16,11): error TS2322: Type 'Mapped3<K>[Uppercase<K>]'
   Type 'Mapped3<K>[Uppercase<string>]' is not assignable to type '{ a: K; }'.
     Type 'Mapped3<K>[string]' is not assignable to type '{ a: K; }'.
 mappedTypeConstraints2.ts(42,7): error TS2322: Type 'Mapped6<K>[keyof Mapped6<K>]' is not assignable to type '`_${string}`'.
-  Type 'Mapped6<K>[`_${string}`]' is not assignable to type '`_${string}`'.
+  Type 'Mapped6<K>[`_${K}`]' is not assignable to type '`_${string}`'.
+    Type 'Mapped6<K>[`_${string}`]' is not assignable to type '`_${string}`'.
 mappedTypeConstraints2.ts(59,57): error TS2322: Type 'Foo<T>[`get${T}`]' is not assignable to type 'T'.
   'T' could be instantiated with an arbitrary type which could be unrelated to 'Foo<T>[`get${T}`]'.
 mappedTypeConstraints2.ts(90,9): error TS2322: Type 'ObjectWithUnderscoredKeys<K>[`_${K}`]' is not assignable to type 'true'.
@@ -63,7 +64,8 @@ mappedTypeConstraints2.ts(90,9): error TS2322: Type 'ObjectWithUnderscoredKeys<K
       let s: `_${string}` = obj[key]; // Error
           ~
 !!! error TS2322: Type 'Mapped6<K>[keyof Mapped6<K>]' is not assignable to type '`_${string}`'.
-!!! error TS2322:   Type 'Mapped6<K>[`_${string}`]' is not assignable to type '`_${string}`'.
+!!! error TS2322:   Type 'Mapped6<K>[`_${K}`]' is not assignable to type '`_${string}`'.
+!!! error TS2322:     Type 'Mapped6<K>[`_${string}`]' is not assignable to type '`_${string}`'.
     }
 
     type Mapped7<K extends string> = {
@@ -119,4 +121,8 @@ mappedTypeConstraints2.ts(90,9): error TS2322: Type 'ObjectWithUnderscoredKeys<K
 !!! error TS2322: Type 'ObjectWithUnderscoredKeys<K>[`_${K}`]' is not assignable to type 'true'.
 !!! error TS2322:   Type 'ObjectWithUnderscoredKeys<K>[`_${string}`]' is not assignable to type 'true'.
     }
+
+    type M2<T> = { [K in keyof T & string as [K] extends ['a'] ? 'x' : 'y']: 1 };
+    function bare<T>(k: keyof M2<T>): 'x' | 'y' { return k; }
+    function inTemplate<T>(k: `p${keyof M2<T>}`): 'px' | 'py' { return k; }
 

tsc/testdata/baselines/reference/conformance/mappedTypeConstraints2.js

@@ -92,6 +92,10 @@ type ObjectWithUnderscoredKeys<K extends string> = {
 function genericTest<K extends string>(objectWithUnderscoredKeys: ObjectWithUnderscoredKeys<K>, key: K) {
   const shouldBeTrue: true = objectWithUnderscoredKeys[`_${key}`]; // assignability fails here, but ideally should not
 }
+
+type M2<T> = { [K in keyof T & string as [K] extends ['a'] ? 'x' : 'y']: 1 };
+function bare<T>(k: keyof M2<T>): 'x' | 'y' { return k; }
+function inTemplate<T>(k: `p${keyof M2<T>}`): 'px' | 'py' { return k; }
 
 
 //// [mappedTypeConstraints2.js]
@@ -132,6 +136,8 @@ function validate(obj, bounds) {
 function genericTest(objectWithUnderscoredKeys, key) {
     const shouldBeTrue = objectWithUnderscoredKeys[`_${key}`]; // assignability fails here, but ideally should not
 }
+function bare(k) { return k; }
+function inTemplate(k) { return k; }
 
 
 //// [mappedTypeConstraints2.d.ts]
@@ -185,3 +191,8 @@ type ObjectWithUnderscoredKeys<K extends string> = {
     [k in K as `_${k}`]: true;
 };
 declare function genericTest<K extends string>(objectWithUnderscoredKeys: ObjectWithUnderscoredKeys<K>, key: K): void;
+type M2<T> = {
+    [K in keyof T & string as [K] extends ['a'] ? 'x' : 'y']: 1;
+};
+declare function bare<T>(k: keyof M2<T>): 'x' | 'y';
+declare function inTemplate<T>(k: `p${keyof M2<T>}`): 'px' | 'py';

tsc/testdata/baselines/reference/conformance/mappedTypeConstraints2.symbols

@@ -316,3 +316,26 @@ function genericTest<K extends string>(objectWithUnderscoredKeys: ObjectWithUnde
 >key : Symbol(key, Decl(mappedTypeConstraints2.ts, 88, 95))
 }
 
+type M2<T> = { [K in keyof T & string as [K] extends ['a'] ? 'x' : 'y']: 1 };
+>M2 : Symbol(M2, Decl(mappedTypeConstraints2.ts, 90, 1))
+>T : Symbol(T, Decl(mappedTypeConstraints2.ts, 92, 8))
+>K : Symbol(K, Decl(mappedTypeConstraints2.ts, 92, 16))
+>T : Symbol(T, Decl(mappedTypeConstraints2.ts, 92, 8))
+>K : Symbol(K, Decl(mappedTypeConstraints2.ts, 92, 16))
+
+function bare<T>(k: keyof M2<T>): 'x' | 'y' { return k; }
+>bare : Symbol(bare, Decl(mappedTypeConstraints2.ts, 92, 77))
+>T : Symbol(T, Decl(mappedTypeConstraints2.ts, 93, 14))
+>k : Symbol(k, Decl(mappedTypeConstraints2.ts, 93, 17))
+>M2 : Symbol(M2, Decl(mappedTypeConstraints2.ts, 90, 1))
+>T : Symbol(T, Decl(mappedTypeConstraints2.ts, 93, 14))
+>k : Symbol(k, Decl(mappedTypeConstraints2.ts, 93, 17))
+
+function inTemplate<T>(k: `p${keyof M2<T>}`): 'px' | 'py' { return k; }
+>inTemplate : Symbol(inTemplate, Decl(mappedTypeConstraints2.ts, 93, 57))
+>T : Symbol(T, Decl(mappedTypeConstraints2.ts, 94, 20))
+>k : Symbol(k, Decl(mappedTypeConstraints2.ts, 94, 23))
+>M2 : Symbol(M2, Decl(mappedTypeConstraints2.ts, 90, 1))
+>T : Symbol(T, Decl(mappedTypeConstraints2.ts, 94, 20))
+>k : Symbol(k, Decl(mappedTypeConstraints2.ts, 94, 23))
+

tsc/testdata/baselines/reference/conformance/mappedTypeConstraints2.types

@@ -228,3 +228,16 @@ function genericTest<K extends string>(objectWithUnderscoredKeys: ObjectWithUnde
 >key : K
 }
 
+type M2<T> = { [K in keyof T & string as [K] extends ['a'] ? 'x' : 'y']: 1 };
+>M2 : M2<T>
+
+function bare<T>(k: keyof M2<T>): 'x' | 'y' { return k; }
+>bare : <T>(k: keyof M2<T>) => 'x' | 'y'
+>k : keyof M2<T>
+>k : "x" | "y"
+
+function inTemplate<T>(k: `p${keyof M2<T>}`): 'px' | 'py' { return k; }
+>inTemplate : <T>(k: `p${keyof M2<T>}`) => 'px' | 'py'
+>k : `p${keyof M2<T>}`
+>k : "px" | "py"
+

tsc/testdata/tests/cases/compiler/mappedTypeAsClauseIntersectionConstraintIndexedAccess.ts

@@ -0,0 +1,17 @@
+// @strict: true
+// @noEmit: true
+
+type ChildPaths<T> = [PathTuples<T>] extends [never] ? [] : PathTuples<T>;
+type PathTuples<T> = T extends object
+  ? {
+      [K in keyof T & string as K extends '_key' ? never : K]: [PathTuples<T[K]>] extends [never]
+        ? never
+        : readonly [K, ...ChildPaths<T[K]>];
+    }[Exclude<keyof T & string, '_key'>]
+  : [];
+
+type T1 = PathTuples<{ a: string; _key: string; b: { c: number } }>;
+const t1: T1 = ['b', 'c'];
+
+type S1<T> = { [K in keyof T & string as K extends '_key' ? never : K]: 1 }[Exclude<keyof T & string, '_key'>];
+type S2<T> = { [K in string & keyof T as K extends '_key' ? never : K]: 1 }[Exclude<string & keyof T, '_key'>];

tsc/testdata/tests/cases/conformance/types/mapped/mappedTypeConstraints2.ts

@@ -93,3 +93,7 @@ type ObjectWithUnderscoredKeys<K extends string> = {
 function genericTest<K extends string>(objectWithUnderscoredKeys: ObjectWithUnderscoredKeys<K>, key: K) {
   const shouldBeTrue: true = objectWithUnderscoredKeys[`_${key}`]; // assignability fails here, but ideally should not
 }
+
+type M2<T> = { [K in keyof T & string as [K] extends ['a'] ? 'x' : 'y']: 1 };
+function bare<T>(k: keyof M2<T>): 'x' | 'y' { return k; }
+function inTemplate<T>(k: `p${keyof M2<T>}`): 'px' | 'py' { return k; }