added subtype option for thrown exceptions

docs/scarpet/language/FunctionsAndControlFlow.md

@@ -295,10 +295,12 @@ Producing:
 {stack: [[<app>, inner_call, 1, 14]], locals: {_a: 0, aaa: booyah, _: 1, _y: 0, _i: 1, _x: 0, _z: 0}, token: [item_tags, 5, 23]}
 ```
 
-### `throw(value?)` `throw(type, value)`
+### `throw(value?)`, `throw(type, value)`, `throw(subtype, type, value)`
 
-Throws an exception that can be caught in a `try` block (see above). If ran without arguments, it will throw `user_exception` 
+Throws an exception that can be caught in a `try` block (see above). If ran without arguments, it will throw a `user_exception` 
 passing `null` as the value to the `catch_expr`. With two arguments you can mimic any other exception type thrown in scarpet.
+With 3 arguments, you can specify a custom exception acting as a `subtype` of a provided `type`, allowing to customize `try` 
+statements with custom exceptions.
 
 ### `if(cond, expr, cond?, expr?, ..., default?)`
 

docs/scarpet/resources/editors/idea/3.txt

@@ -4,6 +4,7 @@ _i
 _x
 _y
 _z
+_trace
 euler
 false
 null

docs/scarpet/resources/editors/npp/scarpet.xml

@@ -91,7 +91,7 @@
             </Keywords>
             <Keywords name="Keywords3">euler pi null true false</Keywords>
             <Keywords name="Keywords4">x y z p</Keywords>
-            <Keywords name="Keywords5">_ _i _a _x _y _z</Keywords>
+            <Keywords name="Keywords5">_ _i _a _x _y _z _trace</Keywords>
             <Keywords name="Keywords6">global_</Keywords>
             <Keywords name="Keywords7">
                 __command

src/main/java/carpet/script/exception/ThrowStatement.java

@@ -24,6 +24,13 @@ public class ThrowStatement extends InternalExpressionException
         this.type = type;
     }
 
+    public ThrowStatement(Value data, Throwables parent, String subtype)
+    {
+        super(subtype);
+        this.data = data;
+        this.type = new Throwables(subtype, parent);
+    }
+
     /**
      * Creates a throw exception.<br>
      * Conveniently creates a value from the {@code value} String

src/main/java/carpet/script/exception/Throwables.java

@@ -1,9 +1,7 @@
 package carpet.script.exception;
 
 import java.util.HashMap;
-import java.util.HashSet;
 import java.util.Map;
-import java.util.Set;
 
 /**
  * This class contains default Scarpet catchable types, as well as their inheritance and
@@ -14,7 +12,6 @@ public class Throwables {
     private final Throwables parent;
 
     private static final Map<String, Throwables> byId = new HashMap<>();
-    private static final Map<String, Set<Throwables>> handles = new HashMap<>();
 
     public static final Throwables THROWN_EXCEPTION_TYPE = register("exception", null);
     public static final Throwables VALUE_EXCEPTION       = register("value_exception", THROWN_EXCEPTION_TYPE);
@@ -44,14 +41,6 @@ public class Throwables {
     {
         Throwables exc = new Throwables(id, parent);
         byId.put(id, exc);
-        Set<Throwables> itHandles = new HashSet<>();
-        itHandles.add(exc);
-        while (parent!=null)
-        {
-            handles.get(parent.id).add(exc);
-            parent = parent.parent;
-        }
-        handles.put(id, itHandles);
         return exc;
     }
 
@@ -61,7 +50,7 @@ public class Throwables {
      * Use an {@link InternalExpressionException} for that
      * @param id The exception's value as a {@link String}
      */
-    protected Throwables(String id, Throwables parent)
+    public Throwables(String id, Throwables parent)
     {
         this.id = id;
         this.parent = parent;
@@ -74,7 +63,6 @@ public class Throwables {
         return properType;
     }
 
-
     /**
      * Checks whether the given filter matches an instance of this exception, by checking equality
      * with itself and possible parents.
@@ -83,9 +71,12 @@ public class Throwables {
      */
     public boolean isRelevantFor(String filter)
     {
-        Set<Throwables> relevantSet = handles.get(filter);
+        return (id.equals(filter) || (parent != null && parent.isRelevantFor(filter)));
-        if (relevantSet == null) throw new InternalExpressionException("Unknown exception type: "+filter);
+    }
-        return relevantSet.contains(this);
+
+    public boolean isUserException()
+    {
+        return this == USER_DEFINED || parent == USER_DEFINED;
     }
 
     /**

src/main/java/carpet/script/language/ControlFlow.java

@@ -61,8 +61,10 @@ public class ControlFlow {
                     throw new ThrowStatement(lv.get(0).evalValue(c), Throwables.USER_DEFINED );
                 case 2:
                     throw new ThrowStatement(lv.get(1).evalValue(c), Throwables.getTypeForException(lv.get(0).evalValue(c).getString()));
+                case 3:
+                    throw new ThrowStatement(lv.get(2).evalValue(c), Throwables.getTypeForException(lv.get(1).evalValue(c).getString()), lv.get(0).evalValue(c).getString());
                 default:
-                    throw new InternalExpressionException("throw() can't accept more than 2 parameters");
+                    throw new InternalExpressionException("throw() can't accept more than 3 parameters");
             }
         });
 
@@ -79,7 +81,7 @@ public class ControlFlow {
             {
                 if (lv.size() == 1)
                 {
-                    if (ret.thrownExceptionType != Throwables.USER_DEFINED)
+                    if (!ret.thrownExceptionType.isUserException())
                         throw ret;
                     return (c_, t_) -> Value.NULL;
                 }
@@ -101,7 +103,7 @@ public class ControlFlow {
                                 NumericValue.of(f.getToken().linepos+1)
                         )).collect(Collectors.toList())),
 
-                        StringValue.of("locals"), MapValue.wrap(ret.context.variables.entrySet().stream().collect(Collectors.toMap(
+                        StringValue.of("locals"), MapValue.wrap(ret.context.variables.entrySet().stream().filter(e -> !e.getKey().equals("_trace")).collect(Collectors.toMap(
                                 e -> StringValue.of(e.getKey()),
                                 e -> e.getValue().evalValue(ret.context)
                         ))),
@@ -114,7 +116,7 @@ public class ControlFlow {
 
                 if (lv.size() == 2)
                 {
-                    if (ret.thrownExceptionType == Throwables.USER_DEFINED)
+                    if (ret.thrownExceptionType.isUserException())
                         val = lv.get(1).evalValue(c, t);
                 }
                 else