Fixed contextual types within generic tuple mapped types

src/compiler/checker.ts

@@ -28943,7 +28943,7 @@ export function createTypeChecker(host: TypeCheckerHost): TypeChecker {
         return !!(getCheckFlags(symbol) & CheckFlags.Mapped && !(symbol as MappedSymbol).links.type && findResolutionCycleStartIndex(symbol, TypeSystemPropertyName.Type) >= 0);
     }
 
-    function getTypeOfPropertyOfContextualType(type: Type, name: __String, nameType?: Type) {
+    function getTypeOfPropertyOfContextualType(type: Type, name: __String, nameType?: Type): Type | undefined {
         return mapType(type, t => {
             if (isGenericMappedType(t) && !t.declaration.nameType) {
                 const constraint = getConstraintTypeFromMappedType(t);
@@ -28959,6 +28959,15 @@ export function createTypeChecker(host: TypeCheckerHost): TypeChecker {
                     return isCircularMappedProperty(prop) ? undefined : getTypeOfSymbol(prop);
                 }
                 if (isTupleType(t) && isNumericLiteralName(name) && +name >= 0) {
+                    if (t.target.hasRestElement) {
+                        const restElement = getTypeArguments(t)[t.target.fixedLength];
+                        if (restElement !== type) {
+                            const propType = getTypeOfPropertyOfContextualType(restElement, name);
+                            if (propType) {
+                                return propType;
+                            }
+                        }
+                    }
                     const restType = getElementTypeOfSliceOfTupleType(t, t.target.fixedLength, /*endSkipCount*/ 0, /*writing*/ false, /*noReductions*/ true);
                     if (restType) {
                         return restType;

tests/baselines/reference/contextuallyTypedElementsOfGenericZippingTuples.symbols

@@ -0,0 +1,92 @@
+=== tests/cases/compiler/contextuallyTypedElementsOfGenericZippingTuples.ts ===
+declare function test<T extends unknown[], T2 extends unknown[]>(
+>test : Symbol(test, Decl(contextuallyTypedElementsOfGenericZippingTuples.ts, 0, 0))
+>T : Symbol(T, Decl(contextuallyTypedElementsOfGenericZippingTuples.ts, 0, 22))
+>T2 : Symbol(T2, Decl(contextuallyTypedElementsOfGenericZippingTuples.ts, 0, 42))
+
+  a: [
+>a : Symbol(a, Decl(contextuallyTypedElementsOfGenericZippingTuples.ts, 0, 65))
+
+    ...{
+      [K in keyof T]: {
+>K : Symbol(K, Decl(contextuallyTypedElementsOfGenericZippingTuples.ts, 3, 7))
+>T : Symbol(T, Decl(contextuallyTypedElementsOfGenericZippingTuples.ts, 0, 22))
+
+        produce: (seed: string) => T[K];
+>produce : Symbol(produce, Decl(contextuallyTypedElementsOfGenericZippingTuples.ts, 3, 23))
+>seed : Symbol(seed, Decl(contextuallyTypedElementsOfGenericZippingTuples.ts, 4, 18))
+>T : Symbol(T, Decl(contextuallyTypedElementsOfGenericZippingTuples.ts, 0, 22))
+>K : Symbol(K, Decl(contextuallyTypedElementsOfGenericZippingTuples.ts, 3, 7))
+
+      };
+    }
+  ],
+  b: [
+>b : Symbol(b, Decl(contextuallyTypedElementsOfGenericZippingTuples.ts, 7, 4))
+
+    ...{
+      [K in keyof T2]: {
+>K : Symbol(K, Decl(contextuallyTypedElementsOfGenericZippingTuples.ts, 10, 7))
+>T2 : Symbol(T2, Decl(contextuallyTypedElementsOfGenericZippingTuples.ts, 0, 42))
+
+        consume: (arg: T[K & keyof T]) => T2[K];
+>consume : Symbol(consume, Decl(contextuallyTypedElementsOfGenericZippingTuples.ts, 10, 24))
+>arg : Symbol(arg, Decl(contextuallyTypedElementsOfGenericZippingTuples.ts, 11, 18))
+>T : Symbol(T, Decl(contextuallyTypedElementsOfGenericZippingTuples.ts, 0, 22))
+>K : Symbol(K, Decl(contextuallyTypedElementsOfGenericZippingTuples.ts, 10, 7))
+>T : Symbol(T, Decl(contextuallyTypedElementsOfGenericZippingTuples.ts, 0, 22))
+>T2 : Symbol(T2, Decl(contextuallyTypedElementsOfGenericZippingTuples.ts, 0, 42))
+>K : Symbol(K, Decl(contextuallyTypedElementsOfGenericZippingTuples.ts, 10, 7))
+
+      };
+    }
+  ]
+): void;
+
+test(
+>test : Symbol(test, Decl(contextuallyTypedElementsOfGenericZippingTuples.ts, 0, 0))
+
+  [
+    {
+      produce: () => "",
+>produce : Symbol(produce, Decl(contextuallyTypedElementsOfGenericZippingTuples.ts, 19, 5))
+
+    },
+    {
+      produce: () => 42,
+>produce : Symbol(produce, Decl(contextuallyTypedElementsOfGenericZippingTuples.ts, 22, 5))
+
+    },
+  ],
+  [
+    {
+      consume: (arg) => {
+>consume : Symbol(consume, Decl(contextuallyTypedElementsOfGenericZippingTuples.ts, 27, 5))
+>arg : Symbol(arg, Decl(contextuallyTypedElementsOfGenericZippingTuples.ts, 28, 16))
+
+        const received: string = arg;
+>received : Symbol(received, Decl(contextuallyTypedElementsOfGenericZippingTuples.ts, 29, 13))
+>arg : Symbol(arg, Decl(contextuallyTypedElementsOfGenericZippingTuples.ts, 28, 16))
+
+        return received;
+>received : Symbol(received, Decl(contextuallyTypedElementsOfGenericZippingTuples.ts, 29, 13))
+
+      },
+    },
+    {
+      consume: (arg) => {
+>consume : Symbol(consume, Decl(contextuallyTypedElementsOfGenericZippingTuples.ts, 33, 5))
+>arg : Symbol(arg, Decl(contextuallyTypedElementsOfGenericZippingTuples.ts, 34, 16))
+
+        const received: number = arg;
+>received : Symbol(received, Decl(contextuallyTypedElementsOfGenericZippingTuples.ts, 35, 13))
+>arg : Symbol(arg, Decl(contextuallyTypedElementsOfGenericZippingTuples.ts, 34, 16))
+
+        return received;
+>received : Symbol(received, Decl(contextuallyTypedElementsOfGenericZippingTuples.ts, 35, 13))
+
+      },
+    },
+  ]
+);
+

tests/baselines/reference/contextuallyTypedElementsOfGenericZippingTuples.types

@@ -0,0 +1,94 @@
+=== tests/cases/compiler/contextuallyTypedElementsOfGenericZippingTuples.ts ===
+declare function test<T extends unknown[], T2 extends unknown[]>(
+>test : <T extends unknown[], T2 extends unknown[]>(a: [...{ [K in keyof T]: { produce: (seed: string) => T[K]; }; }], b: [...{ [K in keyof T2]: { consume: (arg: T[K & keyof T]) => T2[K]; }; }]) => void
+
+  a: [
+>a : [...{ [K in keyof T]: { produce: (seed: string) => T[K]; }; }]
+
+    ...{
+      [K in keyof T]: {
+        produce: (seed: string) => T[K];
+>produce : (seed: string) => T[K]
+>seed : string
+
+      };
+    }
+  ],
+  b: [
+>b : [...{ [K in keyof T2]: { consume: (arg: T[K & keyof T]) => T2[K]; }; }]
+
+    ...{
+      [K in keyof T2]: {
+        consume: (arg: T[K & keyof T]) => T2[K];
+>consume : (arg: T[K & keyof T]) => T2[K]
+>arg : T[K & keyof T]
+
+      };
+    }
+  ]
+): void;
+
+test(
+>test(  [    {      produce: () => "",    },    {      produce: () => 42,    },  ],  [    {      consume: (arg) => {        const received: string = arg;        return received;      },    },    {      consume: (arg) => {        const received: number = arg;        return received;      },    },  ]) : void
+>test : <T extends unknown[], T2 extends unknown[]>(a: [...{ [K in keyof T]: { produce: (seed: string) => T[K]; }; }], b: [...{ [K in keyof T2]: { consume: (arg: T[K & keyof T]) => T2[K]; }; }]) => void
+
+  [
+>[    {      produce: () => "",    },    {      produce: () => 42,    },  ] : [{ produce: () => string; }, { produce: () => number; }]
+    {
+>{      produce: () => "",    } : { produce: () => string; }
+
+      produce: () => "",
+>produce : () => string
+>() => "" : () => string
+>"" : ""
+
+    },
+    {
+>{      produce: () => 42,    } : { produce: () => number; }
+
+      produce: () => 42,
+>produce : () => number
+>() => 42 : () => number
+>42 : 42
+
+    },
+  ],
+  [
+>[    {      consume: (arg) => {        const received: string = arg;        return received;      },    },    {      consume: (arg) => {        const received: number = arg;        return received;      },    },  ] : [{ consume: (arg: string) => string; }, { consume: (arg: number) => number; }]
+    {
+>{      consume: (arg) => {        const received: string = arg;        return received;      },    } : { consume: (arg: string) => string; }
+
+      consume: (arg) => {
+>consume : (arg: string) => string
+>(arg) => {        const received: string = arg;        return received;      } : (arg: string) => string
+>arg : string
+
+        const received: string = arg;
+>received : string
+>arg : string
+
+        return received;
+>received : string
+
+      },
+    },
+    {
+>{      consume: (arg) => {        const received: number = arg;        return received;      },    } : { consume: (arg: number) => number; }
+
+      consume: (arg) => {
+>consume : (arg: number) => number
+>(arg) => {        const received: number = arg;        return received;      } : (arg: number) => number
+>arg : number
+
+        const received: number = arg;
+>received : number
+>arg : number
+
+        return received;
+>received : number
+
+      },
+    },
+  ]
+);
+

tests/cases/compiler/contextuallyTypedElementsOfGenericZippingTuples.ts

@@ -0,0 +1,44 @@
+// @strict: true
+// @noEmit: true
+
+declare function test<T extends unknown[], T2 extends unknown[]>(
+  a: [
+    ...{
+      [K in keyof T]: {
+        produce: (seed: string) => T[K];
+      };
+    }
+  ],
+  b: [
+    ...{
+      [K in keyof T2]: {
+        consume: (arg: T[K & keyof T]) => T2[K];
+      };
+    }
+  ]
+): void;
+
+test(
+  [
+    {
+      produce: () => "",
+    },
+    {
+      produce: () => 42,
+    },
+  ],
+  [
+    {
+      consume: (arg) => {
+        const received: string = arg;
+        return received;
+      },
+    },
+    {
+      consume: (arg) => {
+        const received: number = arg;
+        return received;
+      },
+    },
+  ]
+);