Additional error reports + Add POLYMOD_STRICT_SYNTAX compiler define

polymod/hscript/_internal/Expr.hx

@@ -180,6 +180,7 @@ enum Error
   EClassInvalidSuper; // Accessing "super" in a parentless class
   EScriptThrow(v:Dynamic); // Script called "throw"
   EScriptCallThrow(v:Dynamic); // Script called a function which threw
+  EInvalidAccessorCombination(accessors:Array<String>);
   // Fallback error type.
   ECustom(msg:String);
 }

polymod/hscript/_internal/Parser.hx

@@ -1663,16 +1663,29 @@ class Parser
         case "override":
           access.push(AOverride);
         case "public":
-          access.push(APublic);
+          // Throw an error if the user tries declaring a variable as public when it's already been declared private.
+          if (access.contains(APrivate))
+            error(ECustom("Conflicting access modifier public"), currentPos, currentPos);
+          else if (!access.contains(APublic))
+            access.push(APublic);
         case "private":
-          access.push(APrivate);
+          // Throw an error if the user tries declaring a variable as private when it's already been declared public.
+          if (access.contains(APublic))
+            error(ECustom("Conflicting access modifier private"), currentPos, currentPos);
+          else if (!access.contains(APrivate))
+            access.push(APrivate);
         case "inline":
           access.push(AInline);
         case "static":
           access.push(AStatic);
         case "macro":
           access.push(AMacro);
         case "function":
+          if (access.contains(AOverride) && access.contains(AStatic))
+          {
+            error(EInvalidAccessorCombination(['override', 'static']), currentPos, currentPos);
+          }
+
           var name = getIdent();
           var inf = parseFunctionDecl();
           maybe(TSemicolon);
@@ -1713,6 +1726,13 @@ class Parser
           else
             ensure(TSemicolon);
 
+          #if POLYMOD_STRICT_SYNTAX
+          if (access.contains(AInline) && !access.contains(AStatic))
+          {
+            error(ECustom('Invalid modifier: inline on non-static variable'), currentPos, currentPos);
+          }
+          #end
+
           return {
             name: name,
             meta: meta,

polymod/hscript/_internal/PolymodScriptClass.hx

@@ -181,6 +181,11 @@ class PolymodScriptClass
           Polymod.error(SCRIPT_PARSE_FAILED,
             'Error while parsing class ${path}#${errLine}: EClassUnresolvedSuperclass' + '\n' + 'Unresolved superclass "${cls}", ${reason}', SCRIPT_RUNTIME);
           return false;
+        case EInvalidAccessorCombination(accessors):
+          Polymod.error(
+            SCRIPT_PARSE_FAILED,
+            'Error while parsing function ${path}#${errLine}: EInvalidAccessorCombination' + '\n' + 'Invalid modifier combination: ${accessors.join(' + ')}', SCRIPT_RUNTIME);
+            return false;
         default:
           Polymod.error(SCRIPT_PARSE_FAILED, 'Error while parsing script ${path}#${errLine}: ' + '\n' + 'An unknown error occurred: ${err}', SCRIPT_RUNTIME);
           return false;
@@ -568,18 +573,46 @@ class PolymodScriptClass
       superClass = Type.createInstance(clsToCreate, args);
     }
 
-    // Throw an error if the script class has an instance field with the same name as one from the super class.
     for (f in _c.fields)
     {
       switch (f.kind)
       {
         case KVar(v):
           if (!f.access.contains(AStatic) && superHasField(f.name))
           {
-            throw 'Redefinition of variable "${f.name}" from superclass not allowed';
+            // Throw an error if the script class has an instance field with the same name as one from the super class.
+            throw 'Redefinition of variable "${f.name}" from superclass not allowed.';
           }
+        case KFunction(fn):
+          #if POLYMOD_STRICT_SYNTAX
+          if (f.access.contains(AOverride) && !superHasField(f.name))
+          {
+            // Throw an error if a function is declared overwritten but isn't overriding anything.
+            throw "Field " + f.name + " is declared 'override' but doesn't override any field.";
+          }
+          else if (!f.access.contains(AOverride) && superHasField(f.name))
+          {
+            var superClassPackage:String = '';
+            if (superClass is PolymodScriptClass)
+            {
+              superClassPackage = Util.getFullClassName((cast superClass : PolymodScriptClass)._c);
+            }
+            else
+            {
+              // TODO: Fetch entire package name?
+              superClassPackage = Util.getTypeNameOf(superClass);
+            }
 
-        case _:
+            // Throw an error if a function is overriden but doesn't have the override accessor.
+            throw "Field " + f.name + " should be declared with 'override' since it is inherited from superclass " + superClassPackage + '.';
+          }
+          else if (f.access.contains(AOverride) && superClass == null)
+          {
+            // Throw an error if the override accessor is used with no super class.
+            throw "Invalid modifier: override on field" + f.name + " of class that has no parent.";
+          }
+          #end
+        default:
       }
     }
   }

polymod/hscript/_internal/Printer.hx

@@ -746,6 +746,7 @@ class Printer
       // TODO: Do we need to distinguish these?
       case EScriptCallThrow(v): 'Script threw an exception:\n$v';
       case EScriptThrow(v): 'User script threw an exception:\n$v';
+      case EInvalidAccessorCombination(accessors): 'Invalid modifier combination: ${accessors.join(' + ')}';
       case ECustom(msg): msg;
     };
     #if hscriptPos