Change sentinels to unknown

Author: jack-williams

src/compiler/checker.ts

@@ -692,9 +692,9 @@ namespace ts {
         // in getPropagatingFlagsOfTypes, and it is checked in inferFromTypes.
         anyFunctionType.objectFlags |= ObjectFlags.NonInferrableType;
 
-        const noConstraintType = createAnonymousType(undefined, emptySymbols, emptyArray, emptyArray, undefined, undefined);
-        const circularConstraintType = createAnonymousType(undefined, emptySymbols, emptyArray, emptyArray, undefined, undefined);
-        const resolvingDefaultType = createAnonymousType(undefined, emptySymbols, emptyArray, emptyArray, undefined, undefined);
+        const noConstraintType = createIntrinsicType(TypeFlags.Unknown, "unknown");
+        const circularConstraintType = createIntrinsicType(TypeFlags.Unknown, "unknown");
+        const resolvingDefaultType = createIntrinsicType(TypeFlags.Unknown, "unknown");
 
         const markerSuperType = createTypeParameter();
         const markerSubType = createTypeParameter();
@@ -12735,12 +12735,13 @@ namespace ts {
             function reportRelationError(message: DiagnosticMessage | undefined, source: Type, target: Type) {
                 const [sourceType, targetType] = getTypeNamesForErrorDisplay(source, target);
 
-                if (target.flags & TypeFlags.TypeParameter && target.immediateBaseConstraint !== undefined && isTypeAssignableTo(source, target.immediateBaseConstraint)) {
+                let constraint: Type | undefined;
+                if (target.flags & TypeFlags.TypeParameter && (constraint = getBaseConstraintOfType(target)) && isTypeAssignableTo(source, constraint)) {
                     reportError(
                         Diagnostics._0_is_assignable_to_the_constraint_of_type_1_but_1_could_be_instantiated_with_a_different_subtype_of_constraint_2,
                         sourceType,
                         targetType,
-                        typeToString(target.immediateBaseConstraint),
+                        typeToString(constraint),
                     );
                 }
 

tests/baselines/reference/assignmentCompatWithCallSignatures3.errors.txt

@@ -14,7 +14,6 @@ tests/cases/conformance/types/typeRelationships/assignmentCompatibility/assignme
   Types of parameters 'x' and 'x' are incompatible.
     Types of parameters 'arg' and 'arg' are incompatible.
       Type 'string' is not assignable to type 'T'.
-        'string' is assignable to the constraint of type 'T', but 'T' could be instantiated with a different subtype of constraint '{}'.
 tests/cases/conformance/types/typeRelationships/assignmentCompatibility/assignmentCompatWithCallSignatures3.ts(62,1): error TS2322: Type '(x: (arg: Base) => Derived) => Base' is not assignable to type '<T extends Base, U extends Derived>(x: (arg: T) => U) => T'.
   Types of parameters 'x' and 'x' are incompatible.
     Types of parameters 'arg' and 'arg' are incompatible.
@@ -143,7 +142,6 @@ tests/cases/conformance/types/typeRelationships/assignmentCompatibility/assignme
 !!! error TS2322:   Types of parameters 'x' and 'x' are incompatible.
 !!! error TS2322:     Types of parameters 'arg' and 'arg' are incompatible.
 !!! error TS2322:       Type 'string' is not assignable to type 'T'.
-!!! error TS2322:         'string' is assignable to the constraint of type 'T', but 'T' could be instantiated with a different subtype of constraint '{}'.
     var b6: <T extends Base, U extends Derived>(x: (arg: T) => U) => T; 
     a6 = b6; // ok
     b6 = a6; // ok

tests/baselines/reference/assignmentCompatWithCallSignatures4.errors.txt

@@ -47,7 +47,6 @@ tests/cases/conformance/types/typeRelationships/assignmentCompatibility/assignme
 tests/cases/conformance/types/typeRelationships/assignmentCompatibility/assignmentCompatWithCallSignatures4.ts(89,9): error TS2322: Type '<T>(x: T) => string[]' is not assignable to type '<T>(x: T) => T[]'.
   Type 'string[]' is not assignable to type 'T[]'.
     Type 'string' is not assignable to type 'T'.
-      'string' is assignable to the constraint of type 'T', but 'T' could be instantiated with a different subtype of constraint '{}'.
 tests/cases/conformance/types/typeRelationships/assignmentCompatibility/assignmentCompatWithCallSignatures4.ts(90,9): error TS2322: Type '<T>(x: T) => T[]' is not assignable to type '<T>(x: T) => string[]'.
   Type 'T[]' is not assignable to type 'string[]'.
     Type 'T' is not assignable to type 'string'.
@@ -57,7 +56,6 @@ tests/cases/conformance/types/typeRelationships/assignmentCompatibility/assignme
 tests/cases/conformance/types/typeRelationships/assignmentCompatibility/assignmentCompatWithCallSignatures4.ts(96,9): error TS2322: Type '<T>(x: T) => string[]' is not assignable to type '<T>(x: T) => T[]'.
   Type 'string[]' is not assignable to type 'T[]'.
     Type 'string' is not assignable to type 'T'.
-      'string' is assignable to the constraint of type 'T', but 'T' could be instantiated with a different subtype of constraint '{}'.
 
 
 ==== tests/cases/conformance/types/typeRelationships/assignmentCompatibility/assignmentCompatWithCallSignatures4.ts (15 errors) ====
@@ -211,7 +209,6 @@ tests/cases/conformance/types/typeRelationships/assignmentCompatibility/assignme
 !!! error TS2322: Type '<T>(x: T) => string[]' is not assignable to type '<T>(x: T) => T[]'.
 !!! error TS2322:   Type 'string[]' is not assignable to type 'T[]'.
 !!! error TS2322:     Type 'string' is not assignable to type 'T'.
-!!! error TS2322:       'string' is assignable to the constraint of type 'T', but 'T' could be instantiated with a different subtype of constraint '{}'.
             b2 = a2;
             ~~
 !!! error TS2322: Type '<T>(x: T) => T[]' is not assignable to type '<T>(x: T) => string[]'.
@@ -231,6 +228,5 @@ tests/cases/conformance/types/typeRelationships/assignmentCompatibility/assignme
 !!! error TS2322: Type '<T>(x: T) => string[]' is not assignable to type '<T>(x: T) => T[]'.
 !!! error TS2322:   Type 'string[]' is not assignable to type 'T[]'.
 !!! error TS2322:     Type 'string' is not assignable to type 'T'.
-!!! error TS2322:       'string' is assignable to the constraint of type 'T', but 'T' could be instantiated with a different subtype of constraint '{}'.
         }
     }

tests/baselines/reference/assignmentCompatWithCallSignatures5.errors.txt

@@ -5,13 +5,11 @@ tests/cases/conformance/types/typeRelationships/assignmentCompatibility/assignme
     Type '{ foo: U; bar: U; }' is not assignable to type '{ foo: T; bar: T; }'.
       Types of property 'foo' are incompatible.
         Type 'U' is not assignable to type 'T'.
-          'U' is assignable to the constraint of type 'T', but 'T' could be instantiated with a different subtype of constraint '{}'.
 tests/cases/conformance/types/typeRelationships/assignmentCompatibility/assignmentCompatWithCallSignatures5.ts(55,1): error TS2322: Type '<T>(x: { a: T; b: T; }) => T[]' is not assignable to type '<U, V>(x: { a: U; b: V; }) => U[]'.
   Types of parameters 'x' and 'x' are incompatible.
     Type '{ a: U; b: V; }' is not assignable to type '{ a: U; b: U; }'.
       Types of property 'b' are incompatible.
         Type 'V' is not assignable to type 'U'.
-          'V' is assignable to the constraint of type 'U', but 'U' could be instantiated with a different subtype of constraint '{}'.
 tests/cases/conformance/types/typeRelationships/assignmentCompatibility/assignmentCompatWithCallSignatures5.ts(58,1): error TS2322: Type '<T extends Base>(x: { a: T; b: T; }) => T[]' is not assignable to type '<U, V>(x: { a: U; b: V; }) => U[]'.
   Types of parameters 'x' and 'x' are incompatible.
     Type '{ a: U; b: V; }' is not assignable to type '{ a: Base; b: Base; }'.
@@ -81,7 +79,6 @@ tests/cases/conformance/types/typeRelationships/assignmentCompatibility/assignme
 !!! error TS2322:     Type '{ foo: U; bar: U; }' is not assignable to type '{ foo: T; bar: T; }'.
 !!! error TS2322:       Types of property 'foo' are incompatible.
 !!! error TS2322:         Type 'U' is not assignable to type 'T'.
-!!! error TS2322:           'U' is assignable to the constraint of type 'T', but 'T' could be instantiated with a different subtype of constraint '{}'.
     var b15: <U, V>(x: { a: U; b: V; }) => U[]; 
     a15 = b15; // ok, T = U, T = V
     b15 = a15; // ok
@@ -91,7 +88,6 @@ tests/cases/conformance/types/typeRelationships/assignmentCompatibility/assignme
 !!! error TS2322:     Type '{ a: U; b: V; }' is not assignable to type '{ a: U; b: U; }'.
 !!! error TS2322:       Types of property 'b' are incompatible.
 !!! error TS2322:         Type 'V' is not assignable to type 'U'.
-!!! error TS2322:           'V' is assignable to the constraint of type 'U', but 'U' could be instantiated with a different subtype of constraint '{}'.
     var b16: <T>(x: { a: T; b: T }) => T[]; 
     a15 = b16; // ok
     b15 = a16; // ok

tests/baselines/reference/assignmentCompatWithCallSignatures6.errors.txt

@@ -5,7 +5,6 @@ tests/cases/conformance/types/typeRelationships/assignmentCompatibility/assignme
     Type '{ foo: U; bar: U; }' is not assignable to type '{ foo: T; bar: T; }'.
       Types of property 'foo' are incompatible.
         Type 'U' is not assignable to type 'T'.
-          'U' is assignable to the constraint of type 'T', but 'T' could be instantiated with a different subtype of constraint '{}'.
 tests/cases/conformance/types/typeRelationships/assignmentCompatibility/assignmentCompatWithCallSignatures6.ts(42,1): error TS2322: Type '<T extends Base>(x: { a: T; b: T; }) => T[]' is not assignable to type '<T>(x: { a: T; b: T; }) => T[]'.
   Types of parameters 'x' and 'x' are incompatible.
     Type '{ a: T; b: T; }' is not assignable to type '{ a: Base; b: Base; }'.
@@ -62,7 +61,6 @@ tests/cases/conformance/types/typeRelationships/assignmentCompatibility/assignme
 !!! error TS2322:     Type '{ foo: U; bar: U; }' is not assignable to type '{ foo: T; bar: T; }'.
 !!! error TS2322:       Types of property 'foo' are incompatible.
 !!! error TS2322:         Type 'U' is not assignable to type 'T'.
-!!! error TS2322:           'U' is assignable to the constraint of type 'T', but 'T' could be instantiated with a different subtype of constraint '{}'.
     var b16: <T>(x: { a: T; b: T }) => T[]; 
     x.a16 = b16;
     b16 = x.a16;

tests/baselines/reference/assignmentCompatWithConstructSignatures3.errors.txt

@@ -14,7 +14,6 @@ tests/cases/conformance/types/typeRelationships/assignmentCompatibility/assignme
   Types of parameters 'x' and 'x' are incompatible.
     Types of parameters 'arg' and 'arg' are incompatible.
       Type 'string' is not assignable to type 'T'.
-        'string' is assignable to the constraint of type 'T', but 'T' could be instantiated with a different subtype of constraint '{}'.
 tests/cases/conformance/types/typeRelationships/assignmentCompatibility/assignmentCompatWithConstructSignatures3.ts(62,1): error TS2322: Type 'new (x: (arg: Base) => Derived) => Base' is not assignable to type 'new <T extends Base, U extends Derived>(x: (arg: T) => U) => T'.
   Types of parameters 'x' and 'x' are incompatible.
     Types of parameters 'arg' and 'arg' are incompatible.
@@ -143,7 +142,6 @@ tests/cases/conformance/types/typeRelationships/assignmentCompatibility/assignme
 !!! error TS2322:   Types of parameters 'x' and 'x' are incompatible.
 !!! error TS2322:     Types of parameters 'arg' and 'arg' are incompatible.
 !!! error TS2322:       Type 'string' is not assignable to type 'T'.
-!!! error TS2322:         'string' is assignable to the constraint of type 'T', but 'T' could be instantiated with a different subtype of constraint '{}'.
     var b6: new <T extends Base, U extends Derived>(x: (arg: T) => U) => T; 
     a6 = b6; // ok
     b6 = a6; // ok

tests/baselines/reference/assignmentCompatWithConstructSignatures4.errors.txt

@@ -63,7 +63,6 @@ tests/cases/conformance/types/typeRelationships/assignmentCompatibility/assignme
 tests/cases/conformance/types/typeRelationships/assignmentCompatibility/assignmentCompatWithConstructSignatures4.ts(89,9): error TS2322: Type 'new <T>(x: T) => string[]' is not assignable to type 'new <T>(x: T) => T[]'.
   Type 'string[]' is not assignable to type 'T[]'.
     Type 'string' is not assignable to type 'T'.
-      'string' is assignable to the constraint of type 'T', but 'T' could be instantiated with a different subtype of constraint '{}'.
 tests/cases/conformance/types/typeRelationships/assignmentCompatibility/assignmentCompatWithConstructSignatures4.ts(90,9): error TS2322: Type 'new <T>(x: T) => T[]' is not assignable to type 'new <T>(x: T) => string[]'.
   Type 'T[]' is not assignable to type 'string[]'.
     Type 'T' is not assignable to type 'string'.
@@ -73,7 +72,6 @@ tests/cases/conformance/types/typeRelationships/assignmentCompatibility/assignme
 tests/cases/conformance/types/typeRelationships/assignmentCompatibility/assignmentCompatWithConstructSignatures4.ts(96,9): error TS2322: Type 'new <T>(x: T) => string[]' is not assignable to type 'new <T>(x: T) => T[]'.
   Type 'string[]' is not assignable to type 'T[]'.
     Type 'string' is not assignable to type 'T'.
-      'string' is assignable to the constraint of type 'T', but 'T' could be instantiated with a different subtype of constraint '{}'.
 
 
 ==== tests/cases/conformance/types/typeRelationships/assignmentCompatibility/assignmentCompatWithConstructSignatures4.ts (19 errors) ====
@@ -247,7 +245,6 @@ tests/cases/conformance/types/typeRelationships/assignmentCompatibility/assignme
 !!! error TS2322: Type 'new <T>(x: T) => string[]' is not assignable to type 'new <T>(x: T) => T[]'.
 !!! error TS2322:   Type 'string[]' is not assignable to type 'T[]'.
 !!! error TS2322:     Type 'string' is not assignable to type 'T'.
-!!! error TS2322:       'string' is assignable to the constraint of type 'T', but 'T' could be instantiated with a different subtype of constraint '{}'.
             b2 = a2; // ok
             ~~
 !!! error TS2322: Type 'new <T>(x: T) => T[]' is not assignable to type 'new <T>(x: T) => string[]'.
@@ -267,6 +264,5 @@ tests/cases/conformance/types/typeRelationships/assignmentCompatibility/assignme
 !!! error TS2322: Type 'new <T>(x: T) => string[]' is not assignable to type 'new <T>(x: T) => T[]'.
 !!! error TS2322:   Type 'string[]' is not assignable to type 'T[]'.
 !!! error TS2322:     Type 'string' is not assignable to type 'T'.
-!!! error TS2322:       'string' is assignable to the constraint of type 'T', but 'T' could be instantiated with a different subtype of constraint '{}'.
         }
     }

tests/baselines/reference/assignmentCompatWithConstructSignatures5.errors.txt

@@ -5,13 +5,11 @@ tests/cases/conformance/types/typeRelationships/assignmentCompatibility/assignme
     Type '{ foo: U; bar: U; }' is not assignable to type '{ foo: T; bar: T; }'.
       Types of property 'foo' are incompatible.
         Type 'U' is not assignable to type 'T'.
-          'U' is assignable to the constraint of type 'T', but 'T' could be instantiated with a different subtype of constraint '{}'.
 tests/cases/conformance/types/typeRelationships/assignmentCompatibility/assignmentCompatWithConstructSignatures5.ts(55,1): error TS2322: Type 'new <T>(x: { a: T; b: T; }) => T[]' is not assignable to type 'new <U, V>(x: { a: U; b: V; }) => U[]'.
   Types of parameters 'x' and 'x' are incompatible.
     Type '{ a: U; b: V; }' is not assignable to type '{ a: U; b: U; }'.
       Types of property 'b' are incompatible.
         Type 'V' is not assignable to type 'U'.
-          'V' is assignable to the constraint of type 'U', but 'U' could be instantiated with a different subtype of constraint '{}'.
 tests/cases/conformance/types/typeRelationships/assignmentCompatibility/assignmentCompatWithConstructSignatures5.ts(58,1): error TS2322: Type 'new <T extends Base>(x: { a: T; b: T; }) => T[]' is not assignable to type 'new <U, V>(x: { a: U; b: V; }) => U[]'.
   Types of parameters 'x' and 'x' are incompatible.
     Type '{ a: U; b: V; }' is not assignable to type '{ a: Base; b: Base; }'.
@@ -81,7 +79,6 @@ tests/cases/conformance/types/typeRelationships/assignmentCompatibility/assignme
 !!! error TS2322:     Type '{ foo: U; bar: U; }' is not assignable to type '{ foo: T; bar: T; }'.
 !!! error TS2322:       Types of property 'foo' are incompatible.
 !!! error TS2322:         Type 'U' is not assignable to type 'T'.
-!!! error TS2322:           'U' is assignable to the constraint of type 'T', but 'T' could be instantiated with a different subtype of constraint '{}'.
     var b15: new <U, V>(x: { a: U; b: V; }) => U[]; 
     a15 = b15; // ok
     b15 = a15; // ok
@@ -91,7 +88,6 @@ tests/cases/conformance/types/typeRelationships/assignmentCompatibility/assignme
 !!! error TS2322:     Type '{ a: U; b: V; }' is not assignable to type '{ a: U; b: U; }'.
 !!! error TS2322:       Types of property 'b' are incompatible.
 !!! error TS2322:         Type 'V' is not assignable to type 'U'.
-!!! error TS2322:           'V' is assignable to the constraint of type 'U', but 'U' could be instantiated with a different subtype of constraint '{}'.
     var b16: new <T>(x: { a: T; b: T }) => T[]; 
     a15 = b16; // ok
     b15 = a16; // ok

tests/baselines/reference/assignmentCompatWithConstructSignatures6.errors.txt

@@ -5,7 +5,6 @@ tests/cases/conformance/types/typeRelationships/assignmentCompatibility/assignme
     Type '{ foo: U; bar: U; }' is not assignable to type '{ foo: T; bar: T; }'.
       Types of property 'foo' are incompatible.
         Type 'U' is not assignable to type 'T'.
-          'U' is assignable to the constraint of type 'T', but 'T' could be instantiated with a different subtype of constraint '{}'.
 tests/cases/conformance/types/typeRelationships/assignmentCompatibility/assignmentCompatWithConstructSignatures6.ts(42,1): error TS2322: Type 'new <T extends Base>(x: { a: T; b: T; }) => T[]' is not assignable to type 'new <T>(x: { a: T; b: T; }) => T[]'.
   Types of parameters 'x' and 'x' are incompatible.
     Type '{ a: T; b: T; }' is not assignable to type '{ a: Base; b: Base; }'.
@@ -62,7 +61,6 @@ tests/cases/conformance/types/typeRelationships/assignmentCompatibility/assignme
 !!! error TS2322:     Type '{ foo: U; bar: U; }' is not assignable to type '{ foo: T; bar: T; }'.
 !!! error TS2322:       Types of property 'foo' are incompatible.
 !!! error TS2322:         Type 'U' is not assignable to type 'T'.
-!!! error TS2322:           'U' is assignable to the constraint of type 'T', but 'T' could be instantiated with a different subtype of constraint '{}'.
     var b16: new <T>(x: { a: T; b: T }) => T[]; 
     x.a16 = b16;
     b16 = x.a16;

tests/baselines/reference/assignmentCompatWithGenericCallSignatures2.errors.txt

@@ -1,7 +1,6 @@
 tests/cases/conformance/types/typeRelationships/assignmentCompatibility/assignmentCompatWithGenericCallSignatures2.ts(15,1): error TS2322: Type 'B' is not assignable to type 'A'.
   Types of parameters 'y' and 'y' are incompatible.
     Type 'T[]' is not assignable to type 'T'.
-      'T[]' is assignable to the constraint of type 'T', but 'T' could be instantiated with a different subtype of constraint '{}'.
 tests/cases/conformance/types/typeRelationships/assignmentCompatibility/assignmentCompatWithGenericCallSignatures2.ts(16,1): error TS2322: Type 'A' is not assignable to type 'B'.
   Types of parameters 'y' and 'y' are incompatible.
     Type 'S' is not assignable to type 'S[]'.
@@ -27,7 +26,6 @@ tests/cases/conformance/types/typeRelationships/assignmentCompatibility/assignme
 !!! error TS2322: Type 'B' is not assignable to type 'A'.
 !!! error TS2322:   Types of parameters 'y' and 'y' are incompatible.
 !!! error TS2322:     Type 'T[]' is not assignable to type 'T'.
-!!! error TS2322:       'T[]' is assignable to the constraint of type 'T', but 'T' could be instantiated with a different subtype of constraint '{}'.
     b = a;
     ~
 !!! error TS2322: Type 'A' is not assignable to type 'B'.