Fixed issues with inference from nested tuple types of the same shape (#49226)

src/compiler/checker.ts

@@ -22888,8 +22888,7 @@ export function createTypeChecker(host: TypeCheckerHost): TypeChecker {
                 return type.symbol;
             }
             if (isTupleType(type)) {
-                // Tuple types are tracked through their target type
-                return type.target;
+                return type;
             }
         }
         if (type.flags & TypeFlags.TypeParameter) {

tests/baselines/reference/inferFromNestedSameShapeTuple.symbols

@@ -0,0 +1,86 @@
+=== tests/cases/compiler/inferFromNestedSameShapeTuple.ts ===
+// repro #48524
+
+type Magic<X> = X extends [[infer Y, ...infer _], ...infer __] ? Y : never;
+>Magic : Symbol(Magic, Decl(inferFromNestedSameShapeTuple.ts, 0, 0))
+>X : Symbol(X, Decl(inferFromNestedSameShapeTuple.ts, 2, 11))
+>X : Symbol(X, Decl(inferFromNestedSameShapeTuple.ts, 2, 11))
+>Y : Symbol(Y, Decl(inferFromNestedSameShapeTuple.ts, 2, 33))
+>_ : Symbol(_, Decl(inferFromNestedSameShapeTuple.ts, 2, 45))
+>__ : Symbol(__, Decl(inferFromNestedSameShapeTuple.ts, 2, 58))
+>Y : Symbol(Y, Decl(inferFromNestedSameShapeTuple.ts, 2, 33))
+
+type R = Magic<[[number]]>
+>R : Symbol(R, Decl(inferFromNestedSameShapeTuple.ts, 2, 75))
+>Magic : Symbol(Magic, Decl(inferFromNestedSameShapeTuple.ts, 0, 0))
+
+// repro #52722
+
+type Recursive<Id> = {
+>Recursive : Symbol(Recursive, Decl(inferFromNestedSameShapeTuple.ts, 4, 26))
+>Id : Symbol(Id, Decl(inferFromNestedSameShapeTuple.ts, 8, 15))
+
+    id: Id
+>id : Symbol(id, Decl(inferFromNestedSameShapeTuple.ts, 8, 22))
+>Id : Symbol(Id, Decl(inferFromNestedSameShapeTuple.ts, 8, 15))
+
+    children: readonly Recursive<Id>[]
+>children : Symbol(children, Decl(inferFromNestedSameShapeTuple.ts, 9, 10))
+>Recursive : Symbol(Recursive, Decl(inferFromNestedSameShapeTuple.ts, 4, 26))
+>Id : Symbol(Id, Decl(inferFromNestedSameShapeTuple.ts, 8, 15))
+}
+
+declare function getIds<Id>(items: readonly Recursive<Id>[]): Id[];
+>getIds : Symbol(getIds, Decl(inferFromNestedSameShapeTuple.ts, 11, 1))
+>Id : Symbol(Id, Decl(inferFromNestedSameShapeTuple.ts, 13, 24))
+>items : Symbol(items, Decl(inferFromNestedSameShapeTuple.ts, 13, 28))
+>Recursive : Symbol(Recursive, Decl(inferFromNestedSameShapeTuple.ts, 4, 26))
+>Id : Symbol(Id, Decl(inferFromNestedSameShapeTuple.ts, 13, 24))
+>Id : Symbol(Id, Decl(inferFromNestedSameShapeTuple.ts, 13, 24))
+
+const items = [{
+>items : Symbol(items, Decl(inferFromNestedSameShapeTuple.ts, 15, 5))
+
+    id: 'a',
+>id : Symbol(id, Decl(inferFromNestedSameShapeTuple.ts, 15, 16))
+
+    children: [{
+>children : Symbol(children, Decl(inferFromNestedSameShapeTuple.ts, 16, 12))
+
+        id: 'b',
+>id : Symbol(id, Decl(inferFromNestedSameShapeTuple.ts, 17, 16))
+
+        children: []
+>children : Symbol(children, Decl(inferFromNestedSameShapeTuple.ts, 18, 16))
+
+    }]
+}] as const satisfies readonly Recursive<string>[]
+>const : Symbol(const)
+>Recursive : Symbol(Recursive, Decl(inferFromNestedSameShapeTuple.ts, 4, 26))
+
+const foo = getIds(items)
+>foo : Symbol(foo, Decl(inferFromNestedSameShapeTuple.ts, 23, 5))
+>getIds : Symbol(getIds, Decl(inferFromNestedSameShapeTuple.ts, 11, 1))
+>items : Symbol(items, Decl(inferFromNestedSameShapeTuple.ts, 15, 5))
+
+// variant with a fresh argument
+const foo2 = getIds([{
+>foo2 : Symbol(foo2, Decl(inferFromNestedSameShapeTuple.ts, 26, 5))
+>getIds : Symbol(getIds, Decl(inferFromNestedSameShapeTuple.ts, 11, 1))
+
+    id: 'a',
+>id : Symbol(id, Decl(inferFromNestedSameShapeTuple.ts, 26, 22))
+
+    children: [{
+>children : Symbol(children, Decl(inferFromNestedSameShapeTuple.ts, 27, 12))
+
+        id: 'b',
+>id : Symbol(id, Decl(inferFromNestedSameShapeTuple.ts, 28, 16))
+
+        children: []
+>children : Symbol(children, Decl(inferFromNestedSameShapeTuple.ts, 29, 16))
+
+    }]
+}] as const)
+>const : Symbol(const)
+

tests/baselines/reference/inferFromNestedSameShapeTuple.types

@@ -0,0 +1,86 @@
+=== tests/cases/compiler/inferFromNestedSameShapeTuple.ts ===
+// repro #48524
+
+type Magic<X> = X extends [[infer Y, ...infer _], ...infer __] ? Y : never;
+>Magic : Magic<X>
+
+type R = Magic<[[number]]>
+>R : number
+
+// repro #52722
+
+type Recursive<Id> = {
+>Recursive : Recursive<Id>
+
+    id: Id
+>id : Id
+
+    children: readonly Recursive<Id>[]
+>children : readonly Recursive<Id>[]
+}
+
+declare function getIds<Id>(items: readonly Recursive<Id>[]): Id[];
+>getIds : <Id>(items: readonly Recursive<Id>[]) => Id[]
+>items : readonly Recursive<Id>[]
+
+const items = [{
+>items : readonly [{ readonly id: "a"; readonly children: readonly [{ readonly id: "b"; readonly children: readonly []; }]; }]
+>[{    id: 'a',    children: [{        id: 'b',        children: []    }]}] as const satisfies readonly Recursive<string>[] : readonly [{ readonly id: "a"; readonly children: readonly [{ readonly id: "b"; readonly children: readonly []; }]; }]
+>[{    id: 'a',    children: [{        id: 'b',        children: []    }]}] as const : readonly [{ readonly id: "a"; readonly children: readonly [{ readonly id: "b"; readonly children: readonly []; }]; }]
+>[{    id: 'a',    children: [{        id: 'b',        children: []    }]}] : readonly [{ readonly id: "a"; readonly children: readonly [{ readonly id: "b"; readonly children: readonly []; }]; }]
+>{    id: 'a',    children: [{        id: 'b',        children: []    }]} : { readonly id: "a"; readonly children: readonly [{ readonly id: "b"; readonly children: readonly []; }]; }
+
+    id: 'a',
+>id : "a"
+>'a' : "a"
+
+    children: [{
+>children : readonly [{ readonly id: "b"; readonly children: readonly []; }]
+>[{        id: 'b',        children: []    }] : readonly [{ readonly id: "b"; readonly children: readonly []; }]
+>{        id: 'b',        children: []    } : { readonly id: "b"; readonly children: readonly []; }
+
+        id: 'b',
+>id : "b"
+>'b' : "b"
+
+        children: []
+>children : readonly []
+>[] : readonly []
+
+    }]
+}] as const satisfies readonly Recursive<string>[]
+
+const foo = getIds(items)
+>foo : ("a" | "b")[]
+>getIds(items) : ("a" | "b")[]
+>getIds : <Id>(items: readonly Recursive<Id>[]) => Id[]
+>items : readonly [{ readonly id: "a"; readonly children: readonly [{ readonly id: "b"; readonly children: readonly []; }]; }]
+
+// variant with a fresh argument
+const foo2 = getIds([{
+>foo2 : ("a" | "b")[]
+>getIds([{    id: 'a',    children: [{        id: 'b',        children: []    }]}] as const) : ("a" | "b")[]
+>getIds : <Id>(items: readonly Recursive<Id>[]) => Id[]
+>[{    id: 'a',    children: [{        id: 'b',        children: []    }]}] as const : readonly [{ readonly id: "a"; readonly children: readonly [{ readonly id: "b"; readonly children: readonly []; }]; }]
+>[{    id: 'a',    children: [{        id: 'b',        children: []    }]}] : readonly [{ readonly id: "a"; readonly children: readonly [{ readonly id: "b"; readonly children: readonly []; }]; }]
+>{    id: 'a',    children: [{        id: 'b',        children: []    }]} : { readonly id: "a"; readonly children: readonly [{ readonly id: "b"; readonly children: readonly []; }]; }
+
+    id: 'a',
+>id : "a"
+>'a' : "a"
+
+    children: [{
+>children : readonly [{ readonly id: "b"; readonly children: readonly []; }]
+>[{        id: 'b',        children: []    }] : readonly [{ readonly id: "b"; readonly children: readonly []; }]
+>{        id: 'b',        children: []    } : { readonly id: "b"; readonly children: readonly []; }
+
+        id: 'b',
+>id : "b"
+>'b' : "b"
+
+        children: []
+>children : readonly []
+>[] : readonly []
+
+    }]
+}] as const)

tests/cases/compiler/inferFromNestedSameShapeTuple.ts

@@ -0,0 +1,36 @@
+// @strict: true
+// @noEmit: true
+
+// repro #48524
+
+type Magic<X> = X extends [[infer Y, ...infer _], ...infer __] ? Y : never;
+
+type R = Magic<[[number]]>
+
+// repro #52722
+
+type Recursive<Id> = {
+    id: Id
+    children: readonly Recursive<Id>[]
+}
+
+declare function getIds<Id>(items: readonly Recursive<Id>[]): Id[];
+
+const items = [{
+    id: 'a',
+    children: [{
+        id: 'b',
+        children: []
+    }]
+}] as const satisfies readonly Recursive<string>[]
+
+const foo = getIds(items)
+
+// variant with a fresh argument
+const foo2 = getIds([{
+    id: 'a',
+    children: [{
+        id: 'b',
+        children: []
+    }]
+}] as const)