typescript-eslint · JoshuaKGoldberg · Jan 16, 2024 · Jan 11, 2024 · Jan 13, 2024
diff --git a/packages/eslint-plugin/tests/rules/no-unsafe-argument.test.ts b/packages/eslint-plugin/tests/rules/no-unsafe-argument.test.ts
@@ -92,6 +92,19 @@ toHaveBeenCalledWith(1 as any);
 declare function acceptsMap(arg: Map<string, string>): void;
 acceptsMap(new Map());
     `,
+    `
+type T = [number, T[]];
+declare function foo(t: T): void;
+declare const t: T;
+
+foo(t);
+    `,
+    `
+type T = Array<T>;
+declare function foo<T>(t: T): T;
+const t: T = [];
+foo(t);
+    `,
   ],
   invalid: [
     {
@@ -352,5 +365,25 @@ foo('a', 1 as any, 'a' as any, 1 as any);
         },
       ],
     },
+    {
+      code: `
+type T = [number, T[]];
+declare function foo(t: T): void;
+declare const t: T;
+foo(t as any);
+      `,
+      errors: [
+        {
+          messageId: 'unsafeArgument',
+          line: 5,
+          column: 5,
+          endColumn: 13,
+          data: {
+            sender: 'any',
+            receiver: 'T',
+          },
+        },
+      ],
+    },
   ],
 });
diff --git a/packages/eslint-plugin/tests/rules/no-unsafe-assignment.test.ts b/packages/eslint-plugin/tests/rules/no-unsafe-assignment.test.ts
@@ -114,6 +114,10 @@ class Foo {
     'const x: { y: number } = { y: 1 };',
     'const x = [...[1, 2, 3]];',
     'const [{ [`x${1}`]: x }] = [{ [`x`]: 1 }] as [{ [`x`]: any }];',
+    `
+type T = [string, T[]];
+const test: T = ['string', []] as T;
+    `,
     {
       code: `
 type Props = { a: string };
@@ -371,5 +375,19 @@ function foo() {
         },
       ],
     },
+    {
+      code: `
+type T = [string, T[]];
+const test: T = ['string', []] as any;
+      `,
+      errors: [
+        {
+          messageId: 'anyAssignment',
+          line: 3,
+          column: 7,
+          endColumn: 38,
+        },
+      ],
+    },
   ],
 });
diff --git a/packages/type-utils/src/isUnsafeAssignment.ts b/packages/type-utils/src/isUnsafeAssignment.ts
@@ -20,6 +20,22 @@ export function isUnsafeAssignment(
   receiver: ts.Type,
   checker: ts.TypeChecker,
   senderNode: TSESTree.Node | null,
+): false | { sender: ts.Type; receiver: ts.Type } {
+  return isUnsafeAssignmentWorker(
+    type,
+    receiver,
+    checker,
+    senderNode,
+    new Map(),
+  );
+}
+
+function isUnsafeAssignmentWorker(
+  type: ts.Type,
+  receiver: ts.Type,
+  checker: ts.TypeChecker,
+  senderNode: TSESTree.Node | null,
+  visited: Map<ts.Type, Set<ts.Type>>,
 ): false | { sender: ts.Type; receiver: ts.Type } {
   if (isTypeAnyType(type)) {
     // Allow assignment of any ==> unknown.
@@ -32,6 +48,17 @@ export function isUnsafeAssignment(
     }
   }
 
+  const typeAlreadyVisited = visited.get(type);
+
+  if (typeAlreadyVisited) {
+    if (typeAlreadyVisited.has(receiver)) {
+      return false;
+    }
+    typeAlreadyVisited.add(receiver);
+  } else {
+    visited.set(type, new Set([receiver]));
+  }
+
   if (tsutils.isTypeReference(type) && tsutils.isTypeReference(receiver)) {
     // TODO - figure out how to handle cases like this,
     // where the types are assignable, but not the same type
@@ -72,7 +99,13 @@ export function isUnsafeAssignment(
       const arg = typeArguments[i];
       const receiverArg = receiverTypeArguments[i];
 
-      const unsafe = isUnsafeAssignment(arg, receiverArg, checker, senderNode);
+      const unsafe = isUnsafeAssignmentWorker(
+        arg,
+        receiverArg,
+        checker,
+        senderNode,
+        visited,
+      );
       if (unsafe) {
         return { sender: type, receiver };
       }

diff --git a/packages/type-utils/tests/isUnsafeAssignment.test.ts b/packages/type-utils/tests/isUnsafeAssignment.test.ts
@@ -9,7 +9,10 @@ import { expectToHaveParserServices } from './test-utils/expectToHaveParserServi
 describe('isUnsafeAssignment', () => {
   const rootDir = path.join(__dirname, 'fixtures');
 
-  function getTypes(code: string): {
+  function getTypes(
+    code: string,
+    declarationIndex = 0,
+  ): {
     sender: ts.Type;
     senderNode: TSESTree.Node;
     receiver: ts.Type;
@@ -23,7 +26,9 @@ describe('isUnsafeAssignment', () => {
     expectToHaveParserServices(services);
     const checker = services.program.getTypeChecker();
 
-    const declaration = ast.body[0] as TSESTree.VariableDeclaration;
+    const declaration = ast.body[
+      declarationIndex
+    ] as TSESTree.VariableDeclaration;
     const declarator = declaration.declarations[0];
     return {
       receiver: services.getTypeAtLocation(declarator.id),
@@ -111,6 +116,21 @@ describe('isUnsafeAssignment', () => {
         'Set<Set<Set<string>>>',
       );
     });
+
+    it('circular reference', () => {
+      const { sender, senderNode, receiver, checker } = getTypes(
+        `type T = [string, T[]];
+        const test: T = ["string", []] as any;`,
+        1,
+      );
+
+      expectTypesAre(
+        isUnsafeAssignment(sender, receiver, checker, senderNode),
+        checker,
+        'any',
+        'T',
+      );
+    });
   });
 
   describe('safe', () => {
@@ -202,5 +222,17 @@ describe('isUnsafeAssignment', () => {
         isUnsafeAssignment(sender, receiver, checker, senderNode),
       ).toBeFalsy();
     });
+
+    it('circular reference', () => {
+      const { sender, senderNode, receiver, checker } = getTypes(
+        `type T = [string, T[]];
+        const test: T = ["string", []] as T;`,
+        1,
+      );
+
+      expect(
+        isUnsafeAssignment(sender, receiver, checker, senderNode),
+      ).toBeFalsy();
+    });
   });
 });