fix: Disallow type recursion during type declaration

src/diagnosticMessages.json

@@ -158,6 +158,7 @@
   "Variable '{0}' used before its declaration.": 2448,
   "Cannot redeclare block-scoped variable '{0}'" : 2451,
   "The type argument for type parameter '{0}' cannot be inferred from the usage. Consider specifying the type arguments explicitly.": 2453,
+  "Type alias '{0}' circularly references itself.": 2456,
   "Type '{0}' has no property '{1}'.": 2460,
   "The '{0}' operator cannot be applied to type '{1}'.": 2469,
   "In 'const' enum declarations member initializer must be constant expression.": 2474,

src/parser.ts

@@ -3478,6 +3478,40 @@ export class Parser extends DiagnosticEmitter {
     return null;
   }
 
+  private getRecursiveDepthForTypeDeclaration(
+    identifierName: string,
+    type: TypeNode,
+    depth: i32 = 0
+  ): i32 {
+    switch (type.kind) {
+      case NodeKind.NAMEDTYPE: {
+        let typeArguments = (<NamedTypeNode>type).typeArguments;
+        if (typeArguments) {
+          for (let i = 0, k = typeArguments.length; i < k; i++) {
+            let res = this.getRecursiveDepthForTypeDeclaration(identifierName, typeArguments[i], depth + 1);
+            if (res != -1) return res;
+          }
+        }
+        if ((<NamedTypeNode>type).name.identifier.text == identifierName) {
+          return depth;
+        }
+        break;
+      }
+      case NodeKind.FUNCTIONTYPE: {
+        let fnType = <FunctionTypeNode>type;
+        let res = this.getRecursiveDepthForTypeDeclaration(identifierName, fnType.returnType, depth + 1);
+        if (res != -1) return res;
+        let params = fnType.parameters;
+        for (let i = 0, k = params.length; i < k; i++) {
+          res = this.getRecursiveDepthForTypeDeclaration(identifierName, params[i].type, depth + 1);
+          if (res != -1) return res;
+        }
+        break;
+      }
+    }
+    return -1;
+  }
+
   parseTypeDeclaration(
     tn: Tokenizer,
     flags: CommonFlags,
@@ -3499,6 +3533,21 @@ export class Parser extends DiagnosticEmitter {
         tn.skip(Token.BAR);
         let type = this.parseType(tn);
         if (!type) return null;
+        let depth = this.getRecursiveDepthForTypeDeclaration(name.text, type);
+        if (depth >= 0) {
+          if (depth == 0) {
+            this.error(
+              DiagnosticCode.Type_alias_0_circularly_references_itself,
+              tn.range(), name.text
+            );
+          } else {
+            this.error(
+              DiagnosticCode.Not_implemented_0,
+              tn.range(), "Recursion in type aliases"
+            );
+          }
+          return null;
+        }
         let ret = Node.createTypeDeclaration(
           name,
           decorators,

tests/parser/type.ts

@@ -6,3 +6,13 @@ export type uint64_t = u64;
 export type T1 = | int32_t;
 export type T2 =
   | int32_t;
+
+// disallow type recursion
+export type T3 = T3 | null;
+export type T4 = (x: T4) => i32;
+export type T5 = () => T5;
+export type T6<T> = () => T6<T>;
+export type T7 = Array<T7>;
+export type T8 = Map<string, Array<T8>>;
+export type T9 = Array<() => T9>;
+export type T10 = T6<T10>;

tests/parser/type.ts.fixture.ts

@@ -3,3 +3,11 @@ type int32_t = i32;
 export type uint64_t = u64;
 export type T1 = int32_t;
 export type T2 = int32_t;
+// ERROR 2456: "Type alias 'T3' circularly references itself." in type.ts(11,23+4)
+// ERROR 100: "Not implemented: Recursion in type aliases" in type.ts(12,29+3)
+// ERROR 100: "Not implemented: Recursion in type aliases" in type.ts(13,24+2)
+// ERROR 100: "Not implemented: Recursion in type aliases" in type.ts(14,31+1)
+// ERROR 100: "Not implemented: Recursion in type aliases" in type.ts(15,26+1)
+// ERROR 100: "Not implemented: Recursion in type aliases" in type.ts(16,39+1)
+// ERROR 100: "Not implemented: Recursion in type aliases" in type.ts(17,32+1)
+// ERROR 100: "Not implemented: Recursion in type aliases" in type.ts(18,25+1)