Fixed syntactic truthy semantics for 0n

src/compiler/checker.ts

@@ -44504,9 +44504,10 @@ export function createTypeChecker(host: TypeCheckerHost): TypeChecker {
                     return PredicateSemantics.Sometimes;
                 }
                 return PredicateSemantics.Always;
+            case SyntaxKind.BigIntLiteral:
+                return (node as BigIntLiteral).text !== "0n" ? PredicateSemantics.Always : PredicateSemantics.Never;
             case SyntaxKind.ArrayLiteralExpression:
             case SyntaxKind.ArrowFunction:
-            case SyntaxKind.BigIntLiteral:
             case SyntaxKind.ClassExpression:
             case SyntaxKind.FunctionExpression:
             case SyntaxKind.JsxElement:

tests/baselines/reference/predicateSemantics.errors.txt

@@ -9,9 +9,13 @@ predicateSemantics.ts(33,8): error TS2872: This kind of expression is always tru
 predicateSemantics.ts(34,11): error TS2872: This kind of expression is always truthy.
 predicateSemantics.ts(35,8): error TS2872: This kind of expression is always truthy.
 predicateSemantics.ts(36,8): error TS2872: This kind of expression is always truthy.
+predicateSemantics.ts(47,5): error TS2873: This kind of expression is always falsy.
+predicateSemantics.ts(48,6): error TS2873: This kind of expression is always falsy.
+predicateSemantics.ts(49,5): error TS2872: This kind of expression is always truthy.
+predicateSemantics.ts(50,6): error TS2872: This kind of expression is always truthy.
 
 
-==== predicateSemantics.ts (11 errors) ====
+==== predicateSemantics.ts (15 errors) ====
     declare let cond: any;
 
     // OK: One or other operand is possibly nullish
@@ -77,4 +81,19 @@ predicateSemantics.ts(36,8): error TS2872: This kind of expression is always tru
     function foo(this: Object | undefined) {
         // Should be OK
         return this ?? 0;
-    }
+    }
+
+    // https://github.com/microsoft/TypeScript/issues/60320
+    if (0n) {}
+        ~~
+!!! error TS2873: This kind of expression is always falsy.
+    if (!0n) {}
+         ~~
+!!! error TS2873: This kind of expression is always falsy.
+    if (1n) {}
+        ~~
+!!! error TS2872: This kind of expression is always truthy.
+    if (!1n) {}
+         ~~
+!!! error TS2872: This kind of expression is always truthy.
+

tests/baselines/reference/predicateSemantics.js

@@ -44,18 +44,24 @@ console.log((cond || undefined) && 1 / cond);
 function foo(this: Object | undefined) {
     // Should be OK
     return this ?? 0;
-}
+}
+
+// https://github.com/microsoft/TypeScript/issues/60320
+if (0n) {}
+if (!0n) {}
+if (1n) {}
+if (!1n) {}
+
 
 //// [predicateSemantics.js]
-var _a, _b, _c, _d, _e, _f;
 // OK: One or other operand is possibly nullish
-var test1 = (_a = (cond ? undefined : 32)) !== null && _a !== void 0 ? _a : "possibly reached";
+const test1 = (cond ? undefined : 32) ?? "possibly reached";
 // Not OK: Both operands nullish
-var test2 = (_b = (cond ? undefined : null)) !== null && _b !== void 0 ? _b : "always reached";
+const test2 = (cond ? undefined : null) ?? "always reached";
 // Not OK: Both operands non-nullish
-var test3 = (_c = (cond ? 132 : 17)) !== null && _c !== void 0 ? _c : "unreachable";
+const test3 = (cond ? 132 : 17) ?? "unreachable";
 // Parens
-var test4 = (_d = (cond ? (undefined) : (17))) !== null && _d !== void 0 ? _d : 42;
+const test4 = (cond ? (undefined) : (17)) ?? 42;
 // Should be OK (special case)
 if (!!true) {
 }
@@ -64,19 +70,13 @@ while (0) { }
 while (1) { }
 while (true) { }
 while (false) { }
-var p5 = (_e = {}) !== null && _e !== void 0 ? _e : null;
-var p6 = (_f = 0 > 1) !== null && _f !== void 0 ? _f : null;
-var p7 = null !== null && null !== void 0 ? null : null;
-var p8 = (/** @class */ (function () {
-    function foo() {
-    }
-    return foo;
-}())) && null;
-var p9 = (/** @class */ (function () {
-    function foo() {
-    }
-    return foo;
-}())) || null;
+const p5 = {} ?? null;
+const p6 = 0 > 1 ?? null;
+const p7 = null ?? null;
+const p8 = (class foo {
+}) && null;
+const p9 = (class foo {
+}) || null;
 // Outer expression tests
 while ({}) { }
 while ({}) { }
@@ -86,5 +86,10 @@ while ((({}))) { }
 console.log((cond || undefined) && 1 / cond);
 function foo() {
     // Should be OK
-    return this !== null && this !== void 0 ? this : 0;
+    return this ?? 0;
 }
+// https://github.com/microsoft/TypeScript/issues/60320
+if (0n) { }
+if (!0n) { }
+if (1n) { }
+if (!1n) { }

tests/baselines/reference/predicateSemantics.symbols

@@ -79,3 +79,10 @@ function foo(this: Object | undefined) {
     return this ?? 0;
 >this : Symbol(this, Decl(predicateSemantics.ts, 40, 13))
 }
+
+// https://github.com/microsoft/TypeScript/issues/60320
+if (0n) {}
+if (!0n) {}
+if (1n) {}
+if (!1n) {}
+

tests/baselines/reference/predicateSemantics.types

@@ -234,3 +234,25 @@ function foo(this: Object | undefined) {
 >0 : 0
 >  : ^
 }
+
+// https://github.com/microsoft/TypeScript/issues/60320
+if (0n) {}
+>0n : 0n
+>   : ^^
+
+if (!0n) {}
+>!0n : true
+>    : ^^^^
+>0n : 0n
+>   : ^^
+
+if (1n) {}
+>1n : 1n
+>   : ^^
+
+if (!1n) {}
+>!1n : boolean
+>    : ^^^^^^^
+>1n : 1n
+>   : ^^
+

tests/cases/compiler/predicateSemantics.ts

@@ -1,3 +1,5 @@
+// @target: esnext
+
 declare let cond: any;
 
 // OK: One or other operand is possibly nullish
@@ -41,4 +43,10 @@ console.log((cond || undefined) && 1 / cond);
 function foo(this: Object | undefined) {
     // Should be OK
     return this ?? 0;
-}
+}
+
+// https://github.com/microsoft/TypeScript/issues/60320
+if (0n) {}
+if (!0n) {}
+if (1n) {}
+if (!1n) {}