add <|- generator for overloaded lists again

frontend/parse.icl

@@ -2665,16 +2665,14 @@ where
 		  (lhs_expr, pState) = wantExpression cIsAPattern pState
 		  (token, pState) = nextToken FunctionContext pState
 		| token == LeftArrowToken
-//MW3 was:			= want_generators IsListGenerator (toLineAndColumn qual_position) lhs_expr pState
 			= want_generators IsListGenerator (toLineAndColumn qual_position) qual_filename lhs_expr pState
 		| token == LeftArrowColonToken
-//MW3 was:			= want_generators IsArrayGenerator (toLineAndColumn qual_position) lhs_expr pState
 			= want_generators IsArrayGenerator (toLineAndColumn qual_position) qual_filename lhs_expr pState
+		| token == LeftArrowWithBarToken
+			= want_generators IsOverloadedListGenerator (toLineAndColumn qual_position) qual_filename lhs_expr pState
 			= ({qual_generators = [], qual_filter = No, qual_position = {lc_line = 0, lc_column = 0}, qual_filename = "" },
 					parseError "comprehension: qualifier" (Yes token) "qualifier(s)" pState)
 
-//MW3 was:	want_generators :: !GeneratorKind !LineAndColumn !ParsedExpr !ParseState -> (!Qualifier, !ParseState)
-//MW3 was:	want_generators gen_kind qual_position pattern_exp pState
 	want_generators :: !GeneratorKind !LineAndColumn !FileName !ParsedExpr !ParseState -> (!Qualifier, !ParseState)
 	want_generators gen_kind qual_position qual_filename pattern_exp pState
 		# (gen_position, pState)			= getPosition pState

frontend/syntax.dcl

@@ -1055,10 +1055,7 @@ cNonUniqueSelection	:== False
 					| PS_Array  !ParsedExpr
 					| PS_Erroneous
 
-::	GeneratorKind :== Bool
-
-IsListGenerator 	:== True
-IsArrayGenerator	:== False
+::	GeneratorKind = IsListGenerator | IsOverloadedListGenerator | IsArrayGenerator
 			
 :: LineAndColumn = {lc_line :: !Int, lc_column :: !Int}
 

frontend/syntax.icl

@@ -1050,11 +1050,7 @@ cNonUniqueSelection	:== False
 					| PS_Array  !ParsedExpr
 					| PS_Erroneous
 
-
-::	GeneratorKind :== Bool
-
-IsListGenerator 	:== True
-IsArrayGenerator	:== False
+::	GeneratorKind = IsListGenerator | IsOverloadedListGenerator | IsArrayGenerator
 
 :: LineAndColumn = {lc_line :: !Int, lc_column :: !Int}
 
@@ -1524,7 +1520,11 @@ where
 instance <<< Generator
 where
 	(<<<) file {gen_kind,gen_pattern,gen_expr}
-		= file <<< gen_pattern <<< (if gen_kind "<-" "<-:") <<< gen_expr
+		= file <<< gen_pattern <<< (gen_kind_to_string gen_kind) <<< gen_expr
+	where
+		gen_kind_to_string IsListGenerator = "<-"
+		gen_kind_to_string IsOverloadedListGenerator = "<|-"
+		gen_kind_to_string IsArrayGenerator = "<-:"
 
 instance <<< BasicValue
 where