Exclude identity relation from mapped type relation check (#46632)

* Exclude identity relation from mapped type relation check

* Add regression test

Author: ahejlsberg

src/compiler/checker.ts

@@ -19046,7 +19046,7 @@ namespace ts {
                         originalErrorInfo = undefined;
                     }
                 }
-                else if (isGenericMappedType(target)) {
+                else if (isGenericMappedType(target) && relation !== identityRelation) {
                     // Check if source type `S` is related to target type `{ [P in Q]: T }` or `{ [P in Q as R]: T}`.
                     const keysRemapped = !!target.declaration.nameType;
                     const templateType = getTemplateTypeFromMappedType(target);

tests/baselines/reference/noExcessiveStackDepthError.errors.txt

@@ -0,0 +1,22 @@
+tests/cases/compiler/noExcessiveStackDepthError.ts(13,9): error TS2403: Subsequent variable declarations must have the same type.  Variable 'x' must be of type 'FindConditions<any>', but here has type 'FindConditions<Entity>'.
+
+
+==== tests/cases/compiler/noExcessiveStackDepthError.ts (1 errors) ====
+    // Repro from #46631
+    
+    interface FindOperator<T> {
+        foo: T;
+    }
+    
+    type FindConditions<T> = {
+        [P in keyof T]?: FindConditions<T[P]> | FindOperator<FindConditions<T[P]>>;
+    };
+    
+    function foo<Entity>() {
+        var x: FindConditions<any>;
+        var x: FindConditions<Entity>;  // Excessive stack depth error not expected here
+            ~
+!!! error TS2403: Subsequent variable declarations must have the same type.  Variable 'x' must be of type 'FindConditions<any>', but here has type 'FindConditions<Entity>'.
+!!! related TS6203 tests/cases/compiler/noExcessiveStackDepthError.ts:12:9: 'x' was also declared here.
+    }
+    

tests/baselines/reference/noExcessiveStackDepthError.js

@@ -0,0 +1,34 @@
+//// [noExcessiveStackDepthError.ts]
+// Repro from #46631
+
+interface FindOperator<T> {
+    foo: T;
+}
+
+type FindConditions<T> = {
+    [P in keyof T]?: FindConditions<T[P]> | FindOperator<FindConditions<T[P]>>;
+};
+
+function foo<Entity>() {
+    var x: FindConditions<any>;
+    var x: FindConditions<Entity>;  // Excessive stack depth error not expected here
+}
+
+
+//// [noExcessiveStackDepthError.js]
+"use strict";
+// Repro from #46631
+function foo() {
+    var x;
+    var x; // Excessive stack depth error not expected here
+}
+
+
+//// [noExcessiveStackDepthError.d.ts]
+interface FindOperator<T> {
+    foo: T;
+}
+declare type FindConditions<T> = {
+    [P in keyof T]?: FindConditions<T[P]> | FindOperator<FindConditions<T[P]>>;
+};
+declare function foo<Entity>(): void;

tests/baselines/reference/noExcessiveStackDepthError.symbols

@@ -0,0 +1,43 @@
+=== tests/cases/compiler/noExcessiveStackDepthError.ts ===
+// Repro from #46631
+
+interface FindOperator<T> {
+>FindOperator : Symbol(FindOperator, Decl(noExcessiveStackDepthError.ts, 0, 0))
+>T : Symbol(T, Decl(noExcessiveStackDepthError.ts, 2, 23))
+
+    foo: T;
+>foo : Symbol(FindOperator.foo, Decl(noExcessiveStackDepthError.ts, 2, 27))
+>T : Symbol(T, Decl(noExcessiveStackDepthError.ts, 2, 23))
+}
+
+type FindConditions<T> = {
+>FindConditions : Symbol(FindConditions, Decl(noExcessiveStackDepthError.ts, 4, 1))
+>T : Symbol(T, Decl(noExcessiveStackDepthError.ts, 6, 20))
+
+    [P in keyof T]?: FindConditions<T[P]> | FindOperator<FindConditions<T[P]>>;
+>P : Symbol(P, Decl(noExcessiveStackDepthError.ts, 7, 5))
+>T : Symbol(T, Decl(noExcessiveStackDepthError.ts, 6, 20))
+>FindConditions : Symbol(FindConditions, Decl(noExcessiveStackDepthError.ts, 4, 1))
+>T : Symbol(T, Decl(noExcessiveStackDepthError.ts, 6, 20))
+>P : Symbol(P, Decl(noExcessiveStackDepthError.ts, 7, 5))
+>FindOperator : Symbol(FindOperator, Decl(noExcessiveStackDepthError.ts, 0, 0))
+>FindConditions : Symbol(FindConditions, Decl(noExcessiveStackDepthError.ts, 4, 1))
+>T : Symbol(T, Decl(noExcessiveStackDepthError.ts, 6, 20))
+>P : Symbol(P, Decl(noExcessiveStackDepthError.ts, 7, 5))
+
+};
+
+function foo<Entity>() {
+>foo : Symbol(foo, Decl(noExcessiveStackDepthError.ts, 8, 2))
+>Entity : Symbol(Entity, Decl(noExcessiveStackDepthError.ts, 10, 13))
+
+    var x: FindConditions<any>;
+>x : Symbol(x, Decl(noExcessiveStackDepthError.ts, 11, 7), Decl(noExcessiveStackDepthError.ts, 12, 7))
+>FindConditions : Symbol(FindConditions, Decl(noExcessiveStackDepthError.ts, 4, 1))
+
+    var x: FindConditions<Entity>;  // Excessive stack depth error not expected here
+>x : Symbol(x, Decl(noExcessiveStackDepthError.ts, 11, 7), Decl(noExcessiveStackDepthError.ts, 12, 7))
+>FindConditions : Symbol(FindConditions, Decl(noExcessiveStackDepthError.ts, 4, 1))
+>Entity : Symbol(Entity, Decl(noExcessiveStackDepthError.ts, 10, 13))
+}
+

tests/baselines/reference/noExcessiveStackDepthError.types

@@ -0,0 +1,24 @@
+=== tests/cases/compiler/noExcessiveStackDepthError.ts ===
+// Repro from #46631
+
+interface FindOperator<T> {
+    foo: T;
+>foo : T
+}
+
+type FindConditions<T> = {
+>FindConditions : FindConditions<T>
+
+    [P in keyof T]?: FindConditions<T[P]> | FindOperator<FindConditions<T[P]>>;
+};
+
+function foo<Entity>() {
+>foo : <Entity>() => void
+
+    var x: FindConditions<any>;
+>x : FindConditions<any>
+
+    var x: FindConditions<Entity>;  // Excessive stack depth error not expected here
+>x : FindConditions<any>
+}
+

tests/cases/compiler/noExcessiveStackDepthError.ts

@@ -0,0 +1,17 @@
+// @strict: true
+// @declaration: true
+
+// Repro from #46631
+
+interface FindOperator<T> {
+    foo: T;
+}
+
+type FindConditions<T> = {
+    [P in keyof T]?: FindConditions<T[P]> | FindOperator<FindConditions<T[P]>>;
+};
+
+function foo<Entity>() {
+    var x: FindConditions<any>;
+    var x: FindConditions<Entity>;  // Excessive stack depth error not expected here
+}