fix: raise an error when the asname of import statment is defined multi-times

kclvm/sema/src/resolver/import.rs

@@ -91,6 +91,19 @@ impl<'ctx> Resolver<'ctx> {
                             {
                                 match self.ctx.import_names.get_mut(&self.ctx.filename) {
                                     Some(mapping) => {
+                                        // 'import sub as s' and 'import sub.sub as s' will raise this error.
+                                        // 'import sub' and 'import sub' will not raise this error.
+                                        if mapping.get(&import_stmt.name).is_some()
+                                            && import_stmt.asname.is_some()
+                                        {
+                                            self.handler.add_compile_error(
+                                                &format!(
+                                                    "the name '{}' is defined multiple times, '{}' must be defined only once",
+                                                    import_stmt.name, import_stmt.name
+                                                ),
+                                                stmt.get_span_pos(),
+                                            );
+                                        }
                                         mapping.insert(
                                             import_stmt.name.to_string(),
                                             import_stmt.path.to_string(),

kclvm/sema/src/resolver/test_fail_data/redefine_import/main.k

@@ -0,0 +1,5 @@
+import sub as s
+
+import sub.sub as s
+
+main = s.sub_sub

kclvm/sema/src/resolver/test_fail_data/redefine_import/sub/main.k

@@ -0,0 +1 @@
+sub = "sub"

kclvm/sema/src/resolver/test_fail_data/redefine_import/sub/sub/main.k

@@ -0,0 +1 @@
+sub_sub = "sub_sub"

kclvm/sema/src/resolver/tests.rs

@@ -107,6 +107,30 @@ fn test_resolve_program_fail() {
     }
 }
 
+#[test]
+fn test_resolve_program_redefine() {
+    let sess = Arc::new(ParseSession::default());
+    let mut program = load_program(
+        sess.clone(),
+        &["./src/resolver/test_fail_data/redefine_import/main.k"],
+        None,
+    )
+    .unwrap();
+
+    let scope = resolve_program(&mut program);
+    assert_eq!(scope.handler.diagnostics.len(), 2);
+    let diag = &scope.handler.diagnostics[0];
+    assert_eq!(
+        diag.code,
+        Some(DiagnosticId::Error(ErrorKind::CompileError))
+    );
+    assert_eq!(diag.messages.len(), 1);
+    assert_eq!(
+        diag.messages[0].message,
+        "the name 's' is defined multiple times, 's' must be defined only once"
+    );
+}
+
 #[test]
 fn test_resolve_program_mismatch_type_fail() {
     let mut program = parse_program("./src/resolver/test_fail_data/config_expr.k").unwrap();