FIX: making FORALL behavior compatible with Rebol2 and Red

It looks that someone tried to always reset series position which is processed in `forall` loop.
But it was not working consistently as is described in metaeducation/rebol-issues#2331

Hard to say if it was really Carl, because he would probably not write the removed comment.

Author: Oldes

src/core/n-loop.c

@@ -267,9 +267,7 @@
 	}
 	else Trap_Arg(var);
 
-	// !!!!! ???? allowed to write VAR????
-	*var = *DS_ARG(1);
-
+	*D_RET = *var;
 	return R_RET;
 }
 

src/mezz/base-funcs.r

@@ -101,6 +101,7 @@ cause-error: func [
 			change/only args spec-of first args
 		]
 	]
+	args: head args 
 	; Build and throw the error:
 	do make error! [
 		type: err-type

src/tests/units/series-test.r3

@@ -108,4 +108,35 @@ Rebol [
 	subs: ["1" "foo" "10" "bar"]
 	--assert "bar" = reword/escape "$<10>" subs ["$<" ">"]
 
+===end-group===
+
+===start-group=== "FORALL"
+
+--test-- "Basic FORALL"
+	;-- compatible with R2 & Red - the series is at its tail
+	data: [1 2 3 4]
+	--assert unset? forall data []
+	--assert tail? data
+
+;@@ https://github.com/rebol/rebol-issues/issues/2331
+--test-- "Escaping from FORALL loop using THROW"
+	data: [1 2 3 4]
+	--assert "yes" = catch [forall data [if data/1 = 3 [throw "yes"]]]
+	--assert [3 4] = data
+--test-- "Escaping from FORALL loop using BREAK"
+	data: [1 2 3 4]
+	--assert unset? forall data [if data/1 = 3 [break]]
+	--assert [3 4] = data
+--test-- "Escaping from FORALL loop using BREAK/RETURN"
+	data: [1 2 3 4]
+	--assert forall data [if data/1 = 3 [break/return true]]
+	--assert [3 4] = data
+--test-- "Escaping from FORALL loop on error"
+	data: [1 2 3 4]
+	--assert error? try [forall data [if data/1 = 3 [do make error! "stopped"]]]
+	--assert [3 4] = data
+
+===end-group===
+
+
 ~~~end-file~~~