Make removeSubtypes resilient to reentry

src/compiler/checker.ts

@@ -3572,7 +3572,18 @@ module ts {
             return false;
         }
 
+        // Since removeSubtypes checks the subtype relation, and the subtype relation on a union
+        // may attempt to reduce a union, it is possible that removeSubtypes could be called
+        // recursively on the same set of types.
+        let removeSubtypesStack: string[] = [];
         function removeSubtypes(types: Type[]) {
+            let typeListId = getTypeListId(types);
+            if (removeSubtypesStack.lastIndexOf(typeListId) >= 0) {
+                return;
+            }
+
+            removeSubtypesStack.push(typeListId);
+
             let i = types.length;
             while (i > 0) {
                 i--;
@@ -3580,6 +3591,8 @@ module ts {
                     types.splice(i, 1);
                 }
             }
+
+            removeSubtypesStack.pop();
         }
 
         function containsAnyType(types: Type[]) {

tests/baselines/reference/unionTypeWithRecursiveSubtypeReduction.js

@@ -0,0 +1,43 @@
+//// [unionTypeWithRecursiveSubtypeReduction.ts]
+class Module {
+    public members: Class[];
+}
+
+class Namespace {
+    public members: (Class | Property)[];
+}
+
+class Class {
+    public parent: Namespace;
+}
+
+class Property {
+    public parent: Module | Class;
+}
+
+var t: Class | Property;
+t.parent;
+
+//// [unionTypeWithRecursiveSubtypeReduction.js]
+var Module = (function () {
+    function Module() {
+    }
+    return Module;
+})();
+var Namespace = (function () {
+    function Namespace() {
+    }
+    return Namespace;
+})();
+var Class = (function () {
+    function Class() {
+    }
+    return Class;
+})();
+var Property = (function () {
+    function Property() {
+    }
+    return Property;
+})();
+var t;
+t.parent;

tests/baselines/reference/unionTypeWithRecursiveSubtypeReduction.symbols

@@ -0,0 +1,45 @@
+=== tests/cases/compiler/unionTypeWithRecursiveSubtypeReduction.ts ===
+class Module {
+>Module : Symbol(Module, Decl(unionTypeWithRecursiveSubtypeReduction.ts, 0, 0))
+
+    public members: Class[];
+>members : Symbol(members, Decl(unionTypeWithRecursiveSubtypeReduction.ts, 0, 14))
+>Class : Symbol(Class, Decl(unionTypeWithRecursiveSubtypeReduction.ts, 6, 1))
+}
+
+class Namespace {
+>Namespace : Symbol(Namespace, Decl(unionTypeWithRecursiveSubtypeReduction.ts, 2, 1))
+
+    public members: (Class | Property)[];
+>members : Symbol(members, Decl(unionTypeWithRecursiveSubtypeReduction.ts, 4, 17))
+>Class : Symbol(Class, Decl(unionTypeWithRecursiveSubtypeReduction.ts, 6, 1))
+>Property : Symbol(Property, Decl(unionTypeWithRecursiveSubtypeReduction.ts, 10, 1))
+}
+
+class Class {
+>Class : Symbol(Class, Decl(unionTypeWithRecursiveSubtypeReduction.ts, 6, 1))
+
+    public parent: Namespace;
+>parent : Symbol(parent, Decl(unionTypeWithRecursiveSubtypeReduction.ts, 8, 13))
+>Namespace : Symbol(Namespace, Decl(unionTypeWithRecursiveSubtypeReduction.ts, 2, 1))
+}
+
+class Property {
+>Property : Symbol(Property, Decl(unionTypeWithRecursiveSubtypeReduction.ts, 10, 1))
+
+    public parent: Module | Class;
+>parent : Symbol(parent, Decl(unionTypeWithRecursiveSubtypeReduction.ts, 12, 16))
+>Module : Symbol(Module, Decl(unionTypeWithRecursiveSubtypeReduction.ts, 0, 0))
+>Class : Symbol(Class, Decl(unionTypeWithRecursiveSubtypeReduction.ts, 6, 1))
+}
+
+var t: Class | Property;
+>t : Symbol(t, Decl(unionTypeWithRecursiveSubtypeReduction.ts, 16, 3))
+>Class : Symbol(Class, Decl(unionTypeWithRecursiveSubtypeReduction.ts, 6, 1))
+>Property : Symbol(Property, Decl(unionTypeWithRecursiveSubtypeReduction.ts, 10, 1))
+
+t.parent;
+>t.parent : Symbol(parent, Decl(unionTypeWithRecursiveSubtypeReduction.ts, 8, 13), Decl(unionTypeWithRecursiveSubtypeReduction.ts, 12, 16))
+>t : Symbol(t, Decl(unionTypeWithRecursiveSubtypeReduction.ts, 16, 3))
+>parent : Symbol(parent, Decl(unionTypeWithRecursiveSubtypeReduction.ts, 8, 13), Decl(unionTypeWithRecursiveSubtypeReduction.ts, 12, 16))
+

tests/baselines/reference/unionTypeWithRecursiveSubtypeReduction.types

@@ -0,0 +1,45 @@
+=== tests/cases/compiler/unionTypeWithRecursiveSubtypeReduction.ts ===
+class Module {
+>Module : Module
+
+    public members: Class[];
+>members : Class[]
+>Class : Class
+}
+
+class Namespace {
+>Namespace : Namespace
+
+    public members: (Class | Property)[];
+>members : (Class | Property)[]
+>Class : Class
+>Property : Property
+}
+
+class Class {
+>Class : Class
+
+    public parent: Namespace;
+>parent : Namespace
+>Namespace : Namespace
+}
+
+class Property {
+>Property : Property
+
+    public parent: Module | Class;
+>parent : Module | Class
+>Module : Module
+>Class : Class
+}
+
+var t: Class | Property;
+>t : Class | Property
+>Class : Class
+>Property : Property
+
+t.parent;
+>t.parent : Class | Namespace
+>t : Class | Property
+>parent : Class | Namespace
+

tests/cases/compiler/unionTypeWithRecursiveSubtypeReduction.ts

@@ -0,0 +1,18 @@
+class Module {
+    public members: Class[];
+}
+
+class Namespace {
+    public members: (Class | Property)[];
+}
+
+class Class {
+    public parent: Namespace;
+}
+
+class Property {
+    public parent: Module | Class;
+}
+
+var t: Class | Property;
+t.parent;