Prohibit function parameter redefinition

shivyc/tree/nodes.py

@@ -600,6 +600,8 @@ def _generate_array_ctype(self, decl, prev_ctype):
 
     def _generate_func_ctype(self, decl, prev_ctype):
         """Generate a function ctype from a given a decl_node."""
+        # save identifiers
+        identifiers = []
 
         # Prohibit storage class specifiers in parameters.
         for param in decl.args:
@@ -608,6 +610,14 @@ def _generate_func_ctype(self, decl, prev_ctype):
                 err = "storage class specified for function parameter"
                 raise CompilerError(err, decl_info.range)
 
+            if decl_info.identifier:
+                identifier = str(decl_info.identifier)
+                if identifier not in identifiers:
+                    identifiers.append(str(decl_info.identifier))
+                else:
+                    err = f"redefinition of '{identifier}'"
+                    raise CompilerError(err, decl_info.range)
+
         # Create a new scope because if we create a new struct type inside
         # the function parameters, it should be local to those parameters.
         self.symbol_table.new_scope()

tests/feature_tests/error_declaration.c

@@ -22,6 +22,9 @@ int var1;
 // error: redeclared 'var1' with different linkage
 static int var1;
 
+// error: redefinition of 'a'
+void repeat_param(int a, int a);
+
 int main() {
   // error: variable of incomplete type declared
   void a;