diff --git a/ets2panda/parser/ETSparser.cpp b/ets2panda/parser/ETSparser.cpp
index 2a7ea152f1d0c42814411b6665fbd1e30fd2b4d0..09542e5e65f4bd1247a6289e08c7f10b3aaeb614 100644
--- a/ets2panda/parser/ETSparser.cpp
+++ b/ets2panda/parser/ETSparser.cpp
@@ -1630,6 +1630,16 @@ bool ETSParser::IsFixedArrayTypeNode(ir::AstNode *node)
 
 ir::Expression *ETSParser::ParseFunctionParameter()
 {
+    switch (Lexer()->GetToken().Type()) {
+        case lexer::TokenType::KEYW_PRIVATE:
+        case lexer::TokenType::KEYW_PUBLIC:
+        case lexer::TokenType::KEYW_PROTECTED:
+            LogError(diagnostic::FIELD_IN_PARAM);
+            Lexer()->NextToken();
+        default:
+            break;
+    }
+
     if (Lexer()->GetToken().Type() == lexer::TokenType::PUNCTUATOR_AT) {
         return ParseFunctionParameterAnnotations();
     }
diff --git a/ets2panda/parser/ETSparserExpressions.cpp b/ets2panda/parser/ETSparserExpressions.cpp
index 7a0cb42540017e338534f2b12a247320c7db9296..bff2cbec61e8ca9a642255a35da2c38a699fa4e7 100644
--- a/ets2panda/parser/ETSparserExpressions.cpp
+++ b/ets2panda/parser/ETSparserExpressions.cpp
@@ -359,9 +359,13 @@ ir::Expression *ETSParser::ParsePrimaryExpression(ExpressionParseFlags flags)
         }
         case lexer::TokenType::KEYW_TYPE: {
             LogError(diagnostic::TYPE_ALIAS_ONLY_TOP_LEVEL);
-            const auto &rangeToken = Lexer()->GetToken().Loc();
             ParseTypeAliasDeclaration();  // Try to parse type alias and drop the result.
-            return AllocBrokenExpression(rangeToken);
+            return AllocBrokenExpression(Lexer()->GetToken().Loc());
+        }
+        case lexer::TokenType::KEYW_FUNCTION: {
+            LogError(diagnostic::FUNC_EXPR);
+            ParseFunctionDeclaration(true, ir::ModifierFlags::NONE);
+            return AllocBrokenExpression(Lexer()->GetToken().Loc());
         }
         case lexer::TokenType::PUNCTUATOR_FORMAT: {
             return ParseExpressionFormatPlaceholder();
diff --git a/ets2panda/test/ast/compiler/ets/invalid_two_functions.ets b/ets2panda/test/ast/compiler/ets/invalid_two_functions.ets
index 62d52f75f5cb2155a2d76209841e60a88aca9c41..f4850751e54e1f9d72894560bd436e6a932569d9 100644
--- a/ets2panda/test/ast/compiler/ets/invalid_two_functions.ets
+++ b/ets2panda/test/ast/compiler/ets/invalid_two_functions.ets
@@ -20,5 +20,6 @@ const b = a.map(function (e) {
     return e * 2;
 });
 
-/* @@? 16:2 Error SyntaxError: Unexpected token 'function'. */
-/* @@? 19:17 Error SyntaxError: Unexpected token 'function'. */
+/* @@? 16:2 Error SyntaxError: Function expressions are not supported, use arrow functions instead */
+/* @@? 19:17 Error SyntaxError: Function expressions are not supported, use arrow functions instead */
+/* @@? 19:28 Error SyntaxError: Parameter declaration should have an explicit type annotation. */
diff --git a/ets2panda/test/ast/parser/ets/decl_in_param.ets b/ets2panda/test/ast/parser/ets/decl_in_param.ets
new file mode 100644
index 0000000000000000000000000000000000000000..39e7ac9b8f22cb6f5796d6ff0e57cd8a085c4823
--- /dev/null
+++ b/ets2panda/test/ast/parser/ets/decl_in_param.ets
@@ -0,0 +1,24 @@
+/*
+ * Copyright (c) 2025 Huawei Device Co., Ltd.
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+function f(public x: number){
+}
+class C{
+    constructor(public m:number) {}
+    m(public x:number) {}
+}
+/* @@? 16:12 Error SyntaxError: Declaring fields in parameter list is not supported */
+/* @@? 19:17 Error SyntaxError: Declaring fields in parameter list is not supported */
+/* @@? 20:7 Error SyntaxError: Declaring fields in parameter list is not supported */
diff --git a/ets2panda/test/ast/parser/ets/empty_array_map_inference_fail.ets b/ets2panda/test/ast/parser/ets/empty_array_map_inference_fail.ets
index 0d648f4ea72508aa1f13ee99f58bafac51877434..e085a3efaffb4ed91f7fcca39ce993d05794b0f6 100644
--- a/ets2panda/test/ast/parser/ets/empty_array_map_inference_fail.ets
+++ b/ets2panda/test/ast/parser/ets/empty_array_map_inference_fail.ets
@@ -21,6 +21,7 @@
   return x+1; 
 });
 
-/* @@? 16:2 Error SyntaxError: Unexpected token 'function'. */
+/* @@? 16:2 Error SyntaxError: Function expressions are not supported, use arrow functions instead */
 /* @@? 20:1 Error TypeError: Can't resolve array type */
-/* @@? 20:8 Error SyntaxError: Unexpected token 'function'. */
+/* @@? 20:8 Error SyntaxError: Function expressions are not supported, use arrow functions instead */
+/* @@? 20:18 Error SyntaxError: Parameter declaration should have an explicit type annotation. */
diff --git a/ets2panda/util/diagnostic/syntax.yaml b/ets2panda/util/diagnostic/syntax.yaml
index 8a1a9bafa9cc0a3418103f5191e12558fdcde633..c576b1fe9a0dc899183473b15436d0a13946b007 100644
--- a/ets2panda/util/diagnostic/syntax.yaml
+++ b/ets2panda/util/diagnostic/syntax.yaml
@@ -1267,3 +1267,11 @@ syntax:
 - name: GENERATOR_FUNCTION
   id: 314
   message: "Generator functions are not supported, please use async/await mechanism for multitasking"
+
+- name: FIELD_IN_PARAM
+  id: 315
+  message: "Declaring fields in parameter list is not supported"
+
+- name: FUNC_EXPR
+  id: 316
+  message: "Function expressions are not supported, use arrow functions instead"