consistently check expressions with >, >=, <, <= for unconstrained types in strictNullChecks

src/compiler/checker.ts

@@ -24887,12 +24887,17 @@ export function createTypeChecker(host: TypeCheckerHost): TypeChecker {
 
     // This like getBaseTypeOfLiteralType, but instead treats enum literals as strings/numbers instead
     // of returning their enum base type (which depends on the types of other literals in the enum).
-    function getBaseTypeOfLiteralTypeForComparison(type: Type): Type {
-        return type.flags & (TypeFlags.StringLiteral | TypeFlags.TemplateLiteral | TypeFlags.StringMapping) ? stringType :
+    // It also checks if the type used in the comparison may be undefined or null (or is unknown/unconstrained)
+    function getBaseTypeForComparison(type: Type): Type {
+        return type.flags & TypeFlags.Instantiable && strictNullChecks ? getBaseConstraintOfType(type) ?? unknownUnionType :
+            type.flags & (TypeFlags.StringLiteral | TypeFlags.TemplateLiteral | TypeFlags.StringMapping) ? stringType :
             type.flags & (TypeFlags.NumberLiteral | TypeFlags.Enum) ? numberType :
             type.flags & TypeFlags.BigIntLiteral ? bigintType :
             type.flags & TypeFlags.BooleanLiteral ? booleanType :
-            type.flags & TypeFlags.Union ? mapType(type, getBaseTypeOfLiteralTypeForComparison) :
+            type.flags & TypeFlags.Union ? mapType(type, getBaseTypeForComparison) :
+            type.flags & TypeFlags.Intersection && every((type as IntersectionType).types, t => {
+                    return getBaseTypeForComparison(t) === unknownUnionType;
+                }) ? unknownUnionType :
             type;
     }
 
@@ -39677,8 +39682,8 @@ export function createTypeChecker(host: TypeCheckerHost): TypeChecker {
             case SyntaxKind.LessThanEqualsToken:
             case SyntaxKind.GreaterThanEqualsToken:
                 if (checkForDisallowedESSymbolOperand(operator)) {
-                    leftType = getBaseTypeOfLiteralTypeForComparison(checkNonNullType(leftType, left));
-                    rightType = getBaseTypeOfLiteralTypeForComparison(checkNonNullType(rightType, right));
+                    leftType = checkNonNullType(getBaseTypeForComparison(leftType), left);
+                    rightType = checkNonNullType(getBaseTypeForComparison(rightType), right);
                     reportOperatorErrorUnless((left, right) => {
                         if (isTypeAny(left) || isTypeAny(right)) {
                             return true;

tests/baselines/reference/unconstrainedTypeComparison.errors.txt

@@ -0,0 +1,185 @@
+unconstrainedTypeComparison.ts(2,12): error TS18049: 'a' is possibly 'null' or 'undefined'.
+unconstrainedTypeComparison.ts(2,16): error TS18049: 'b' is possibly 'null' or 'undefined'.
+unconstrainedTypeComparison.ts(6,12): error TS18049: 'a' is possibly 'null' or 'undefined'.
+unconstrainedTypeComparison.ts(6,16): error TS18049: 'b' is possibly 'null' or 'undefined'.
+unconstrainedTypeComparison.ts(10,12): error TS18046: 'a' is of type 'unknown'.
+unconstrainedTypeComparison.ts(10,16): error TS18046: 'b' is of type 'unknown'.
+unconstrainedTypeComparison.ts(14,12): error TS18049: 'a' is possibly 'null' or 'undefined'.
+unconstrainedTypeComparison.ts(14,16): error TS18049: 'b' is possibly 'null' or 'undefined'.
+unconstrainedTypeComparison.ts(18,12): error TS18049: 'a' is possibly 'null' or 'undefined'.
+unconstrainedTypeComparison.ts(18,16): error TS18049: 'b' is possibly 'null' or 'undefined'.
+unconstrainedTypeComparison.ts(22,12): error TS18046: 'a' is of type 'unknown'.
+unconstrainedTypeComparison.ts(22,16): error TS18046: 'b' is of type 'unknown'.
+unconstrainedTypeComparison.ts(26,12): error TS18048: 'a' is possibly 'undefined'.
+unconstrainedTypeComparison.ts(26,16): error TS18048: 'b' is possibly 'undefined'.
+unconstrainedTypeComparison.ts(30,12): error TS18047: 'a' is possibly 'null'.
+unconstrainedTypeComparison.ts(30,16): error TS18047: 'b' is possibly 'null'.
+unconstrainedTypeComparison.ts(34,12): error TS18049: 'a' is possibly 'null' or 'undefined'.
+unconstrainedTypeComparison.ts(34,16): error TS18049: 'b' is possibly 'null' or 'undefined'.
+unconstrainedTypeComparison.ts(38,12): error TS18049: 'x' is possibly 'null' or 'undefined'.
+unconstrainedTypeComparison.ts(38,16): error TS18049: 'y' is possibly 'null' or 'undefined'.
+unconstrainedTypeComparison.ts(42,12): error TS18049: 'x' is possibly 'null' or 'undefined'.
+unconstrainedTypeComparison.ts(42,16): error TS18049: 'y' is possibly 'null' or 'undefined'.
+unconstrainedTypeComparison.ts(49,12): error TS18047: 'x' is possibly 'null'.
+unconstrainedTypeComparison.ts(49,16): error TS18049: 'y' is possibly 'null' or 'undefined'.
+unconstrainedTypeComparison.ts(56,12): error TS18047: 'x' is possibly 'null'.
+unconstrainedTypeComparison.ts(56,16): error TS18049: 'y' is possibly 'null' or 'undefined'.
+unconstrainedTypeComparison.ts(60,12): error TS18049: 'x' is possibly 'null' or 'undefined'.
+unconstrainedTypeComparison.ts(60,16): error TS18049: 'y' is possibly 'null' or 'undefined'.
+unconstrainedTypeComparison.ts(74,12): error TS18047: 'x' is possibly 'null'.
+unconstrainedTypeComparison.ts(74,16): error TS18048: 'y' is possibly 'undefined'.
+unconstrainedTypeComparison.ts(85,12): error TS18047: 'a' is possibly 'null'.
+unconstrainedTypeComparison.ts(85,16): error TS18048: 'b' is possibly 'undefined'.
+
+
+==== unconstrainedTypeComparison.ts (32 errors) ====
+    function f1<T>(a: T, b: T): boolean {
+        return a > b;
+               ~
+!!! error TS18049: 'a' is possibly 'null' or 'undefined'.
+                   ~
+!!! error TS18049: 'b' is possibly 'null' or 'undefined'.
+    }
+
+    function f2<T extends {} | undefined | null>(a: T, b: T): boolean {
+        return a > b;
+               ~
+!!! error TS18049: 'a' is possibly 'null' or 'undefined'.
+                   ~
+!!! error TS18049: 'b' is possibly 'null' or 'undefined'.
+    }
+
+    function f3<T extends unknown>(a: T, b: T): boolean {
+        return a > b;
+               ~
+!!! error TS18046: 'a' is of type 'unknown'.
+                   ~
+!!! error TS18046: 'b' is of type 'unknown'.
+    }
+
+    function f4<T, U extends T>(a: U, b: U): boolean {
+        return a > b;
+               ~
+!!! error TS18049: 'a' is possibly 'null' or 'undefined'.
+                   ~
+!!! error TS18049: 'b' is possibly 'null' or 'undefined'.
+    }
+
+    function f5<T extends {} | undefined | null, U extends T>(a: U, b: U): boolean {
+        return a > b;
+               ~
+!!! error TS18049: 'a' is possibly 'null' or 'undefined'.
+                   ~
+!!! error TS18049: 'b' is possibly 'null' or 'undefined'.
+    }
+
+    function f6<T extends unknown, U extends T>(a: U, b: U): boolean {
+        return a > b;
+               ~
+!!! error TS18046: 'a' is of type 'unknown'.
+                   ~
+!!! error TS18046: 'b' is of type 'unknown'.
+    }
+
+    function f7<T extends {} | undefined, U extends T>(a: U, b: U): boolean {
+        return a > b;
+               ~
+!!! error TS18048: 'a' is possibly 'undefined'.
+                   ~
+!!! error TS18048: 'b' is possibly 'undefined'.
+    }
+
+    function f8<T extends {} | null, U extends T>(a: U, b: U): boolean {
+        return a > b;
+               ~
+!!! error TS18047: 'a' is possibly 'null'.
+                   ~
+!!! error TS18047: 'b' is possibly 'null'.
+    }
+
+    function f9<T extends undefined | null, U extends T>(a: U, b: U): boolean {
+        return a > b;
+               ~
+!!! error TS18049: 'a' is possibly 'null' or 'undefined'.
+                   ~
+!!! error TS18049: 'b' is possibly 'null' or 'undefined'.
+    }
+
+    function f10<T, U>(x: T | U, y: T | U) {
+        return x < y;
+               ~
+!!! error TS18049: 'x' is possibly 'null' or 'undefined'.
+                   ~
+!!! error TS18049: 'y' is possibly 'null' or 'undefined'.
+    }
+
+    function f11<T, U extends T>(x: T | number, y: U | number) {
+        return x < y;
+               ~
+!!! error TS18049: 'x' is possibly 'null' or 'undefined'.
+                   ~
+!!! error TS18049: 'y' is possibly 'null' or 'undefined'.
+    }
+
+    function f12<T, U extends T>(x: T | number, y: U | number) {
+        if (x === undefined) {
+            return false;
+        }
+        return x < y;
+               ~
+!!! error TS18047: 'x' is possibly 'null'.
+                   ~
+!!! error TS18049: 'y' is possibly 'null' or 'undefined'.
+    }
+
+    function f13<T, U extends T | number>(x: U, y: U) {
+        if (x === undefined) {
+            return false;
+        }
+        return x < y;
+               ~
+!!! error TS18047: 'x' is possibly 'null'.
+                   ~
+!!! error TS18049: 'y' is possibly 'null' or 'undefined'.
+    }
+
+    function f14<T, U>(x: T & U, y: T & U) {
+        return x < y;
+               ~
+!!! error TS18049: 'x' is possibly 'null' or 'undefined'.
+                   ~
+!!! error TS18049: 'y' is possibly 'null' or 'undefined'.
+    }
+
+    function f15<T, U extends T>(x: T & number, y: U & number) {
+        return x < y;
+    }
+
+    function f16<T, U extends T>(x: T & U, y: U) {
+        if (x === undefined) {
+            return false;
+        }
+        if (y === null) {
+            return false;
+        }
+        return x < y;
+               ~
+!!! error TS18047: 'x' is possibly 'null'.
+                   ~
+!!! error TS18048: 'y' is possibly 'undefined'.
+    }
+
+
+    function compare<T>(a: T, b: T): boolean {
+        if (a === undefined) {
+            return false;
+        }
+        if (b === null) {
+            return false;
+        }
+        return a > b;
+               ~
+!!! error TS18047: 'a' is possibly 'null'.
+                   ~
+!!! error TS18048: 'b' is possibly 'undefined'.
+    }