feat(semantic): add TS2309 error for export assignment with other exports

crates/oxc_semantic/src/checker/mod.rs

@@ -14,6 +14,7 @@ pub fn check<'a>(kind: AstKind<'a>, ctx: &SemanticBuilder<'a>) {
         AstKind::Program(program) => {
             js::check_duplicate_class_elements(ctx);
             js::check_unresolved_exports(program, ctx);
+            ts::check_ts_export_assignment_in_program(program, ctx);
         }
         AstKind::BindingIdentifier(ident) => {
             js::check_identifier(&ident.name, ident.span, ident.symbol_id.get(), ctx);

crates/oxc_semantic/src/checker/typescript.rs

@@ -157,6 +157,7 @@ fn not_allowed_namespace_declaration(span: Span) -> OxcDiagnostic {
 
 pub fn check_ts_module_declaration<'a>(decl: &TSModuleDeclaration<'a>, ctx: &SemanticBuilder<'a>) {
     check_ts_module_or_global_declaration(decl.span, ctx);
+    check_ts_export_assignment_in_module_decl(decl, ctx);
 }
 
 pub fn check_ts_global_declaration<'a>(decl: &TSGlobalDeclaration<'a>, ctx: &SemanticBuilder<'a>) {
@@ -449,3 +450,66 @@ pub fn check_jsx_expression_container(
         ctx.error(jsx_expressions_may_not_use_the_comma_operator(container.expression.span()));
     }
 }
+
+fn ts_export_assignment_cannot_be_used_with_other_exports(span: Span) -> OxcDiagnostic {
+    ts_error("2309", "An export assignment cannot be used in a module with other exported elements")
+        .with_label(span)
+        .with_help("If you want to use `export =`, remove other `export`s and put all of them to the right hand value of `export =`. If you want to use `export`s, remove `export =` statement.")
+}
+
+pub fn check_ts_export_assignment_in_program<'a>(program: &Program<'a>, ctx: &SemanticBuilder<'a>) {
+    if !ctx.source_type.is_typescript() {
+        return;
+    }
+    check_ts_export_assignment_in_statements(&program.body, ctx);
+}
+
+fn check_ts_export_assignment_in_module_decl<'a>(
+    module_decl: &TSModuleDeclaration<'a>,
+    ctx: &SemanticBuilder<'a>,
+) {
+    let Some(body) = &module_decl.body else {
+        return;
+    };
+    match body {
+        TSModuleDeclarationBody::TSModuleDeclaration(nested) => {
+            check_ts_export_assignment_in_module_decl(nested, ctx);
+        }
+        TSModuleDeclarationBody::TSModuleBlock(block) => {
+            check_ts_export_assignment_in_statements(&block.body, ctx);
+        }
+    }
+}
+
+fn check_ts_export_assignment_in_statements<'a>(
+    statements: &[Statement<'a>],
+    ctx: &SemanticBuilder<'a>,
+) {
+    let mut export_assignment_spans = vec![];
+    let mut has_other_exports = false;
+
+    for stmt in statements {
+        match stmt {
+            Statement::TSExportAssignment(export_assignment) => {
+                export_assignment_spans.push(export_assignment.span);
+            }
+            Statement::ExportNamedDeclaration(export_decl) => {
+                // ignore `export {}`
+                if export_decl.declaration.is_none() && export_decl.specifiers.is_empty() {
+                    continue;
+                }
+                has_other_exports = true;
+            }
+            Statement::ExportDefaultDeclaration(_) | Statement::ExportAllDeclaration(_) => {
+                has_other_exports = true;
+            }
+            _ => {}
+        }
+    }
+
+    if has_other_exports {
+        for span in export_assignment_spans {
+            ctx.error(ts_export_assignment_cannot_be_used_with_other_exports(span));
+        }
+    }
+}

tasks/coverage/misc/fail/export-equal-with-normal-export.ts

@@ -0,0 +1,5 @@
+export const foo = 1;
+export const bar = 2;
+
+export = 3;
+export = 4;

tasks/coverage/snapshots/parser_misc.snap

@@ -1,7 +1,7 @@
 parser_misc Summary:
 AST Parsed     : 52/52 (100.00%)
 Positive Passed: 52/52 (100.00%)
-Negative Passed: 120/120 (100.00%)
+Negative Passed: 121/121 (100.00%)
 
   × Cannot assign to 'arguments' in strict mode
    ╭─[misc/fail/arguments-eval.ts:1:10]
@@ -79,6 +79,23 @@ Negative Passed: 120/120 (100.00%)
    ╰────
   help: for octal literals use the '0o' prefix instead
 
+  × TS(2309): An export assignment cannot be used in a module with other exported elements
+   ╭─[misc/fail/export-equal-with-normal-export.ts:4:1]
+ 3 │ 
+ 4 │ export = 3;
+   · ───────────
+ 5 │ export = 4;
+   ╰────
+  help: If you want to use `export =`, remove other `export`s and put all of them to the right hand value of `export =`. If you want to use `export`s, remove `export =` statement.
+
+  × TS(2309): An export assignment cannot be used in a module with other exported elements
+   ╭─[misc/fail/export-equal-with-normal-export.ts:5:1]
+ 4 │ export = 3;
+ 5 │ export = 4;
+   · ───────────
+   ╰────
+  help: If you want to use `export =`, remove other `export`s and put all of them to the right hand value of `export =`. If you want to use `export`s, remove `export =` statement.
+
   × Expected `,` or `]` but found `const`
    ╭─[misc/fail/imbalanced-array-expr.js:2:1]
  1 │ const foo = [0, 1