fix(linter/vars-on-top): false positive with typescript declare block

crates/oxc_linter/src/rules/eslint/vars_on_top.rs

@@ -99,6 +99,12 @@ impl Rule for VarsOnTop {
         if declaration.kind != VariableDeclarationKind::Var {
             return;
         }
+
+        // Skip TypeScript ambient declarations (declare global, declare module, etc.)
+        if is_in_ambient_typescript_context(node, ctx) {
+            return;
+        }
+
         let parent = ctx.nodes().parent_node(node.id());
 
         match parent.kind() {
@@ -219,6 +225,17 @@ fn check_var_on_top_in_function_scope(
     false
 }
 
+fn is_in_ambient_typescript_context(node: &AstNode, ctx: &LintContext) -> bool {
+    ctx.nodes().ancestors(node.id()).any(|ancestor| {
+        if let AstKind::TSModuleDeclaration(module) = ancestor.kind() {
+            // Ambient if it has the `declare` keyword or is a `declare global` block
+            module.declare || module.kind.is_global()
+        } else {
+            false
+        }
+    })
+}
+
 #[test]
 fn test() {
     use crate::tester::Tester;
@@ -387,6 +404,15 @@ fn test() {
 			        let x;
 			    }
 			}", // {                "ecmaVersion": 2022            }
+        "declare global {
+			    var __CUSTOM_FLAG__: boolean | undefined;
+			}",
+        "declare module 'foo' {
+			    var x: string;
+			}",
+        "declare namespace MyNamespace {
+			    var y: number;
+			}",
     ];
 
     let fail = vec![
@@ -532,6 +558,7 @@ fn test() {
 			            var x;
 			    }
 			}", // {                "ecmaVersion": 2022            }
+        "namespace MyNamespace { const y: number = 123; var z: string; }",
     ];
 
     Tester::new(VarsOnTop::NAME, VarsOnTop::PLUGIN, pass, fail).test_and_snapshot();

crates/oxc_linter/src/snapshots/eslint_vars_on_top.snap

@@ -229,3 +229,10 @@ source: crates/oxc_linter/src/tester.rs
  5 │                 }
    ╰────
   help: Consider moving this to the top of the functions scope or using let or const to declare this variable.
+
+  ⚠ eslint(vars-on-top): All 'var' declarations must be at the top of the function scope.
+   ╭─[vars_on_top.tsx:1:48]
+ 1 │ namespace MyNamespace { const y: number = 123; var z: string; }
+   ·                                                ──────────────
+   ╰────
+  help: Consider moving this to the top of the functions scope or using let or const to declare this variable.