Improved ERROR:

core/classes/tuple/tuple-tests.factor

@@ -656,3 +656,28 @@ T{ reshape-test f "hi" } "tuple" set
 TUPLE: boa-coercer-test { x array-capacity } ;
 
 [ fixnum ] [ 0 >bignum boa-coercer-test boa x>> class ] unit-test
+
+! Test error classes
+ERROR: error-class-test a b c ;
+
+[ "( a b c -- * )" ] [ \ error-class-test stack-effect effect>string ] unit-test
+[ f ] [ \ error-class-test "inline" word-prop ] unit-test
+
+[ "IN: classes.tuple.tests ERROR: error-x ; : error-x 3 ;" eval ]
+[ error>> error>> redefine-error? ] must-fail-with
+
+DEFER: error-y
+
+[ ] [ [ \ error-y forget-class ] with-compilation-unit ] unit-test
+
+[ ] [ "IN: classes.tuple.tests GENERIC: error-y" eval ] unit-test
+
+[ f ] [ \ error-y tuple-class? ] unit-test
+
+[ t ] [ \ error-y generic? ] unit-test
+
+[ ] [ "IN: classes.tuple.tests ERROR: error-y ;" eval ] unit-test
+
+[ t ] [ \ error-y tuple-class? ] unit-test
+
+[ f ] [ \ error-y generic? ] unit-test

core/classes/tuple/tuple.factor

@@ -4,7 +4,7 @@ USING: arrays definitions hashtables kernel kernel.private math
 namespaces sequences sequences.private strings vectors words
 quotations memory combinators generic classes classes.algebra
 classes.private slots.deprecated slots.private slots
-compiler.units math.private accessors assocs ;
+compiler.units math.private accessors assocs effects ;
 IN: classes.tuple
 
 M: tuple class 1 slot 2 slot { word } declare ;
@@ -255,9 +255,13 @@ M: tuple-class define-tuple-class
     3dup tuple-class-unchanged?
     [ 3drop ] [ redefine-tuple-class ] if ;
 
+: thrower-effect ( slots -- effect )
+    [ dup array? [ first ] when ] map f <effect> t >>terminated? ;
+
 : define-error-class ( class superclass slots -- )
-    [ define-tuple-class ] [ 2drop ] 3bi
+    [ define-tuple-class ]
-    dup [ boa throw ] curry define ;
+    [ [ dup [ boa throw ] curry ] [ drop ] [ thrower-effect ] tri* ] 3bi
+    define-declared ;
 
 M: tuple-class reset-class
     [

core/syntax/syntax.factor

@@ -175,6 +175,7 @@ IN: bootstrap.syntax
 
     "ERROR:" [
         parse-tuple-definition
+        pick reset-generic
         pick save-location
         define-error-class
     ] define-syntax