Merge pull request microsoft#3157 from Microsoft/fixUnionReduction

Fix infinite recursion in union type reduction

Author: ahejlsberg

src/compiler/checker.ts

@@ -88,6 +88,7 @@ module ts {
  let undefinedType = createIntrinsicType(TypeFlags.Undefined | TypeFlags.ContainsUndefinedOrNull, "undefined");
  let nullType = createIntrinsicType(TypeFlags.Null | TypeFlags.ContainsUndefinedOrNull, "null");
  let unknownType = createIntrinsicType(TypeFlags.Any, "unknown");
+ let circularType = createIntrinsicType(TypeFlags.Any, "__circular__");
 
  let emptyObjectType = createAnonymousType(undefined, emptySymbols, emptyArray, emptyArray, undefined, undefined);
  let anyFunctionType = createAnonymousType(undefined, emptySymbols, emptyArray, emptyArray, undefined, undefined);
@@ -3575,28 +3576,14 @@ 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. The removeSubtypesStack is used to track which
- // sets of types are currently undergoing subtype reduction.
- 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--;
  if (isSubtypeOfAny(types[i], types)) {
  types.splice(i, 1);
  }
  }
-
- removeSubtypesStack.pop();
  }
 
  function containsAnyType(types: Type[]) {
@@ -3651,10 +3638,20 @@ module ts {
  return type;
  }
 
+ // Subtype reduction is basically an optimization we do to avoid excessively large union types, which take longer
+ // to process and look strange in quick info and error messages. Semantically there is no difference between the
+ // reduced type and the type itself. So, when we detect a circularity we simply say that the reduced type is the
+ // type itself.
  function getReducedTypeOfUnionType(type: UnionType): Type {
- // If union type was created without subtype reduction, perform the deferred reduction now
  if (!type.reducedType) {
- type.reducedType = getUnionType(type.types, /*noSubtypeReduction*/ false);
+ type.reducedType = circularType;
+ let reducedType = getUnionType(type.types, /*noSubtypeReduction*/ false);
+ if (type.reducedType === circularType) {
+ type.reducedType = reducedType;
+ }
+ }
+ else if (type.reducedType === circularType) {
+ type.reducedType = type;
  }
  return type.reducedType;
  }

tests/baselines/reference/unionTypeWithRecursiveSubtypeReduction.js renamed to tests/baselines/reference/unionTypeWithRecursiveSubtypeReduction1.js

@@ -1,4 +1,4 @@
-//// [unionTypeWithRecursiveSubtypeReduction.ts]
+//// [unionTypeWithRecursiveSubtypeReduction1.ts]
 class Module {
  public members: Class[];
 }
@@ -16,9 +16,10 @@ class Property {
 }
 
 var t: Class | Property;
-t.parent;
+t.parent;
+
 
-//// [unionTypeWithRecursiveSubtypeReduction.js]
+//// [unionTypeWithRecursiveSubtypeReduction1.js]
 var Module = (function () {
  function Module() {
  }

tests/baselines/reference/unionTypeWithRecursiveSubtypeReduction.symbols renamed to tests/baselines/reference/unionTypeWithRecursiveSubtypeReduction1.symbols

@@ -1,45 +1,45 @@
-=== tests/cases/compiler/unionTypeWithRecursiveSubtypeReduction.ts ===
+=== tests/cases/compiler/unionTypeWithRecursiveSubtypeReduction1.ts ===
 class Module {
->Module : Symbol(Module, Decl(unionTypeWithRecursiveSubtypeReduction.ts, 0, 0))
+>Module : Symbol(Module, Decl(unionTypeWithRecursiveSubtypeReduction1.ts, 0, 0))
 
  public members: Class[];
->members : Symbol(members, Decl(unionTypeWithRecursiveSubtypeReduction.ts, 0, 14))
->Class : Symbol(Class, Decl(unionTypeWithRecursiveSubtypeReduction.ts, 6, 1))
+>members : Symbol(members, Decl(unionTypeWithRecursiveSubtypeReduction1.ts, 0, 14))
+>Class : Symbol(Class, Decl(unionTypeWithRecursiveSubtypeReduction1.ts, 6, 1))
 }
 
 class Namespace {
->Namespace : Symbol(Namespace, Decl(unionTypeWithRecursiveSubtypeReduction.ts, 2, 1))
+>Namespace : Symbol(Namespace, Decl(unionTypeWithRecursiveSubtypeReduction1.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))
+>members : Symbol(members, Decl(unionTypeWithRecursiveSubtypeReduction1.ts, 4, 17))
+>Class : Symbol(Class, Decl(unionTypeWithRecursiveSubtypeReduction1.ts, 6, 1))
+>Property : Symbol(Property, Decl(unionTypeWithRecursiveSubtypeReduction1.ts, 10, 1))
 }
 
 class Class {
->Class : Symbol(Class, Decl(unionTypeWithRecursiveSubtypeReduction.ts, 6, 1))
+>Class : Symbol(Class, Decl(unionTypeWithRecursiveSubtypeReduction1.ts, 6, 1))
 
  public parent: Namespace;
->parent : Symbol(parent, Decl(unionTypeWithRecursiveSubtypeReduction.ts, 8, 13))
->Namespace : Symbol(Namespace, Decl(unionTypeWithRecursiveSubtypeReduction.ts, 2, 1))
+>parent : Symbol(parent, Decl(unionTypeWithRecursiveSubtypeReduction1.ts, 8, 13))
+>Namespace : Symbol(Namespace, Decl(unionTypeWithRecursiveSubtypeReduction1.ts, 2, 1))
 }
 
 class Property {
->Property : Symbol(Property, Decl(unionTypeWithRecursiveSubtypeReduction.ts, 10, 1))
+>Property : Symbol(Property, Decl(unionTypeWithRecursiveSubtypeReduction1.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))
+>parent : Symbol(parent, Decl(unionTypeWithRecursiveSubtypeReduction1.ts, 12, 16))
+>Module : Symbol(Module, Decl(unionTypeWithRecursiveSubtypeReduction1.ts, 0, 0))
+>Class : Symbol(Class, Decl(unionTypeWithRecursiveSubtypeReduction1.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 : Symbol(t, Decl(unionTypeWithRecursiveSubtypeReduction1.ts, 16, 3))
+>Class : Symbol(Class, Decl(unionTypeWithRecursiveSubtypeReduction1.ts, 6, 1))
+>Property : Symbol(Property, Decl(unionTypeWithRecursiveSubtypeReduction1.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))
+>t.parent : Symbol(parent, Decl(unionTypeWithRecursiveSubtypeReduction1.ts, 8, 13), Decl(unionTypeWithRecursiveSubtypeReduction1.ts, 12, 16))
+>t : Symbol(t, Decl(unionTypeWithRecursiveSubtypeReduction1.ts, 16, 3))
+>parent : Symbol(parent, Decl(unionTypeWithRecursiveSubtypeReduction1.ts, 8, 13), Decl(unionTypeWithRecursiveSubtypeReduction1.ts, 12, 16))
 

tests/baselines/reference/unionTypeWithRecursiveSubtypeReduction.types renamed to tests/baselines/reference/unionTypeWithRecursiveSubtypeReduction1.types

@@ -1,4 +1,4 @@
-=== tests/cases/compiler/unionTypeWithRecursiveSubtypeReduction.ts ===
+=== tests/cases/compiler/unionTypeWithRecursiveSubtypeReduction1.ts ===
 class Module {
 >Module : Module
 

tests/baselines/reference/unionTypeWithRecursiveSubtypeReduction2.errors.txt

@@ -42,4 +42,5 @@ tests/cases/compiler/unionTypeWithRecursiveSubtypeReduction2.ts(20,1): error TS2
 !!! error TS2322: Types of property 'parent' are incompatible.
 !!! error TS2322: Type 'Namespace' is not assignable to type 'Module | Class'.
 !!! error TS2322: Type 'Namespace' is not assignable to type 'Class'.
-!!! error TS2322: Property 'parent' is missing in type 'Namespace'.
+!!! error TS2322: Property 'parent' is missing in type 'Namespace'.
+ 

tests/baselines/reference/unionTypeWithRecursiveSubtypeReduction2.js

@@ -18,7 +18,8 @@ class Property {
 var c: Class;
 var p: Property;
 c = p;
-p = c;
+p = c;
+
 
 //// [unionTypeWithRecursiveSubtypeReduction2.js]
 var Module = (function () {

tests/baselines/reference/unionTypeWithRecursiveSubtypeReduction3.errors.txt

@@ -0,0 +1,14 @@
+tests/cases/compiler/unionTypeWithRecursiveSubtypeReduction3.ts(5,5): error TS2322: Type '{ prop: number; } | { prop: { prop: number; } | any; }' is not assignable to type 'string'.
+ Type '{ prop: number; }' is not assignable to type 'string'.
+
+
+==== tests/cases/compiler/unionTypeWithRecursiveSubtypeReduction3.ts (1 errors) ====
+ var a27: { prop: number } | { prop: T27 };
+ type T27 = typeof a27;
+ 
+ var b: T27;
+ var s: string = b;
+ ~
+!!! error TS2322: Type '{ prop: number; } | { prop: { prop: number; } | any; }' is not assignable to type 'string'.
+!!! error TS2322: Type '{ prop: number; }' is not assignable to type 'string'.
+ 

tests/baselines/reference/unionTypeWithRecursiveSubtypeReduction3.js

@@ -0,0 +1,12 @@
+//// [unionTypeWithRecursiveSubtypeReduction3.ts]
+var a27: { prop: number } | { prop: T27 };
+type T27 = typeof a27;
+
+var b: T27;
+var s: string = b;
+
+
+//// [unionTypeWithRecursiveSubtypeReduction3.js]
+var a27;
+var b;
+var s = b;

tests/cases/compiler/unionTypeWithRecursiveSubtypeReduction.ts renamed to tests/cases/compiler/unionTypeWithRecursiveSubtypeReduction1.ts

@@ -15,4 +15,4 @@ class Property {
 }
 
 var t: Class | Property;
-t.parent;
+t.parent;

tests/cases/compiler/unionTypeWithRecursiveSubtypeReduction2.ts

@@ -17,4 +17,4 @@ class Property {
 var c: Class;
 var p: Property;
 c = p;
-p = c;
+p = c;