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

kclvm/cmd/src/test_data/multi_import/main.k

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

kclvm/cmd/src/test_data/multi_import/sub/main.k

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

kclvm/cmd/src/test_data/multi_import/sub/sub/main.k

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

kclvm/cmd/src/tests.rs

@@ -596,3 +596,22 @@ fn test_error_message_fuzz_unmatched() {
         }
     }
 }
+
+#[test]
+fn test_multi_import() {
+    let test_case_path = PathBuf::from("./src/test_data/multi_import/main.k");
+    let matches = app().arg_required_else_help(true).get_matches_from(&[
+        ROOT_CMD,
+        "run",
+        &test_case_path.canonicalize().unwrap().display().to_string(),
+    ]);
+    let settings = must_build_settings(matches.subcommand_matches("run").unwrap());
+    let sess = Arc::new(ParseSession::default());
+    match exec_program(sess.clone(), &settings.try_into().unwrap()) {
+        Ok(_) => panic!("unreachable code."),
+        Err(msg) => {
+            assert!(msg
+                .contains("the name 's' is defined multiple times, 's' must be defined only once"))
+        }
+    }
+}

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(),