Address review feedback: fix triple negation in checker.ts and add .d.ts test

Co-authored-by: RyanCavanaugh <6685088+RyanCavanaugh@users.noreply.github.com>

Author: Copilot

package-lock.json

@@ -68,7 +68,7 @@
         "fast-xml-parser": "^4.5.2",
         "glob": "^10.4.5",
         "globals": "^15.15.0",
-        "hereby": "^1.10.0",
+        "hereby": "^1.11.0",
         "jsonc-parser": "^3.3.1",
         "knip": "^5.44.4",
         "minimist": "^1.2.8",

package.json

@@ -53179,8 +53179,7 @@ export function createTypeChecker(host: TypeCheckerHost): TypeChecker {
             isPrefixUnaryExpression(node.parent) && isLiteralTypeNode(node.parent.parent);
         if (!literalType) {
             // Don't error on BigInt literals in ambient contexts
-            const inAmbientContext = !!(node.flags & NodeFlags.Ambient);
-            if (!inAmbientContext && languageVersion < ScriptTarget.ES2020) {
+            if (!(node.flags & NodeFlags.Ambient) && languageVersion < ScriptTarget.ES2020) {
                 if (grammarErrorOnNode(node, Diagnostics.BigInt_literals_are_not_available_when_targeting_lower_than_ES2020)) {
                     return true;
                 }

src/compiler/checker.ts

@@ -1,7 +1,13 @@
-bigintAmbientMinimal.ts(5,17): error TS2737: BigInt literals are not available when targeting lower than ES2020.
+/main.ts(5,17): error TS2737: BigInt literals are not available when targeting lower than ES2020.
 
 
-==== bigintAmbientMinimal.ts (1 errors) ====
+==== /ambient.d.ts (0 errors) ====
+    declare const fromDts = 789n;
+    declare namespace Lib {
+        const value = 999n;
+    }
+    
+==== /main.ts (1 errors) ====
     // Minimal repro from issue
     declare const n = 123n;
 

tests/baselines/reference/bigintAmbientMinimal.errors.txt

@@ -1,12 +1,18 @@
 //// [tests/cases/compiler/bigintAmbientMinimal.ts] ////
 
-//// [bigintAmbientMinimal.ts]
+//// [ambient.d.ts]
+declare const fromDts = 789n;
+declare namespace Lib {
+    const value = 999n;
+}
+
+//// [main.ts]
 // Minimal repro from issue
 declare const n = 123n;
 
 // Non-ambient for comparison
 const regular = 456n;
 
-//// [bigintAmbientMinimal.js]
+//// [main.js]
 // Non-ambient for comparison
 var regular = 456n;

tests/baselines/reference/bigintAmbientMinimal.js

@@ -1,11 +1,22 @@
 //// [tests/cases/compiler/bigintAmbientMinimal.ts] ////
 
-=== bigintAmbientMinimal.ts ===
+=== /ambient.d.ts ===
+declare const fromDts = 789n;
+>fromDts : Symbol(fromDts, Decl(ambient.d.ts, 0, 13))
+
+declare namespace Lib {
+>Lib : Symbol(Lib, Decl(ambient.d.ts, 0, 29))
+
+    const value = 999n;
+>value : Symbol(value, Decl(ambient.d.ts, 2, 9))
+}
+
+=== /main.ts ===
 // Minimal repro from issue
 declare const n = 123n;
->n : Symbol(n, Decl(bigintAmbientMinimal.ts, 1, 13))
+>n : Symbol(n, Decl(main.ts, 1, 13))
 
 // Non-ambient for comparison
 const regular = 456n;
->regular : Symbol(regular, Decl(bigintAmbientMinimal.ts, 4, 5))
+>regular : Symbol(regular, Decl(main.ts, 4, 5))
 

tests/baselines/reference/bigintAmbientMinimal.symbols

@@ -1,6 +1,24 @@
 //// [tests/cases/compiler/bigintAmbientMinimal.ts] ////
 
-=== bigintAmbientMinimal.ts ===
+=== /ambient.d.ts ===
+declare const fromDts = 789n;
+>fromDts : 789n
+>        : ^^^^
+>789n : 789n
+>     : ^^^^
+
+declare namespace Lib {
+>Lib : typeof Lib
+>    : ^^^^^^^^^^
+
+    const value = 999n;
+>value : 999n
+>      : ^^^^
+>999n : 999n
+>     : ^^^^
+}
+
+=== /main.ts ===
 // Minimal repro from issue
 declare const n = 123n;
 >n : 123n

tests/baselines/reference/bigintAmbientMinimal.types

@@ -1,5 +1,12 @@
 // @target: ES5
 
+// @Filename: /ambient.d.ts
+declare const fromDts = 789n;
+declare namespace Lib {
+    const value = 999n;
+}
+
+// @Filename: /main.ts
 // Minimal repro from issue
 declare const n = 123n;