diff --git a/parser/macro.go b/parser/macro.go
index dc47b420..dcd23225 100644
--- a/parser/macro.go
+++ b/parser/macro.go
@@ -259,8 +259,13 @@ var (
 
 	// ExistsOneMacro expands "range.exists_one(var, predicate)", which is true if for exactly one
 	// element in range the predicate holds.
+	// Deprecated: Use ExistsOneMacroNew
 	ExistsOneMacro = NewReceiverMacro(operators.ExistsOne, 2, MakeExistsOne)
 
+	// ExistsOneMacroNew expands "range.existsOne(var, predicate)", which is true if for exactly one
+	// element in range the predicate holds.
+	ExistsOneMacroNew = NewReceiverMacro("existsOne", 2, MakeExistsOne)
+
 	// MapMacro expands "range.map(var, function)" into a comprehension which applies the function
 	// to each element in the range to produce a new list.
 	MapMacro = NewReceiverMacro(operators.Map, 2, MakeMap)
@@ -280,6 +285,7 @@ var (
 		AllMacro,
 		ExistsMacro,
 		ExistsOneMacro,
+		ExistsOneMacroNew,
 		MapMacro,
 		MapFilterMacro,
 		FilterMacro,
@@ -336,6 +342,9 @@ func MakeMap(eh ExprHelper, target ast.Expr, args []ast.Expr) (ast.Expr, *common
 	if !found {
 		return nil, eh.NewError(args[0].ID(), "argument is not an identifier")
 	}
+	if v == AccumulatorName {
+		return nil, eh.NewError(args[0].ID(), "iteration variable overwrites accumulator variable")
+	}
 
 	var fn ast.Expr
 	var filter ast.Expr
@@ -366,6 +375,9 @@ func MakeFilter(eh ExprHelper, target ast.Expr, args []ast.Expr) (ast.Expr, *com
 	if !found {
 		return nil, eh.NewError(args[0].ID(), "argument is not an identifier")
 	}
+	if v == AccumulatorName {
+		return nil, eh.NewError(args[0].ID(), "iteration variable overwrites accumulator variable")
+	}
 
 	filter := args[1]
 	init := eh.NewList()
@@ -389,6 +401,9 @@ func makeQuantifier(kind quantifierKind, eh ExprHelper, target ast.Expr, args []
 	if !found {
 		return nil, eh.NewError(args[0].ID(), "argument must be a simple name")
 	}
+	if v == AccumulatorName {
+		return nil, eh.NewError(args[0].ID(), "iteration variable overwrites accumulator variable")
+	}
 
 	var init ast.Expr
 	var condition ast.Expr
diff --git a/parser/parser_test.go b/parser/parser_test.go
index 72bb587f..f174c8fe 100644
--- a/parser/parser_test.go
+++ b/parser/parser_test.go
@@ -438,6 +438,13 @@ var testCases = []testInfo{
 			m^#2:*expr.Expr_IdentExpr#.f^#3:*expr.Expr_SelectExpr#
 		  )^#4:has#`,
 	},
+	{
+		I: `has(m)`,
+		E: `ERROR: <input>:1:5: invalid argument to has() macro
+             | has(m)
+             | ....^`,
+	},
+
 	{
 		I: `m.exists(v, f)`,
 		P: `__comprehension__(
@@ -495,7 +502,7 @@ var testCases = []testInfo{
 		  	)^#11:all#`,
 	},
 	{
-		I: `m.exists_one(v, f)`,
+		I: `m.existsOne(v, f)`,
 		P: `__comprehension__(
 			// Variable
 			v,
@@ -521,10 +528,16 @@ var testCases = []testInfo{
 				__result__^#12:*expr.Expr_IdentExpr#,
 				1^#13:*expr.Constant_Int64Value#
 			)^#14:*expr.Expr_CallExpr#)^#15:*expr.Expr_ComprehensionExpr#`,
-		M: `m^#1:*expr.Expr_IdentExpr#.exists_one(
+		M: `m^#1:*expr.Expr_IdentExpr#.existsOne(
 			v^#3:*expr.Expr_IdentExpr#,
 			f^#4:*expr.Expr_IdentExpr#
-		  	)^#15:exists_one#`,
+		  	)^#15:existsOne#`,
+	},
+	{
+		I: `[].existsOne(__result__, __result__)`,
+		E: `ERROR: <input>:1:14: iteration variable overwrites accumulator variable
+             | [].existsOne(__result__, __result__)
+             | .............^`,
 	},
 	{
 		I: `m.map(v, f)`,
@@ -553,7 +566,12 @@ var testCases = []testInfo{
 			f^#4:*expr.Expr_IdentExpr#
 		  	)^#11:map#`,
 	},
-
+	{
+		I: `m.map(__result__, __result__)`,
+		E: `ERROR: <input>:1:7: iteration variable overwrites accumulator variable
+             | m.map(__result__, __result__)
+             | ......^`,
+	},
 	{
 		I: `m.map(v, p, f)`,
 		P: `__comprehension__(
@@ -618,6 +636,18 @@ var testCases = []testInfo{
 			p^#4:*expr.Expr_IdentExpr#
 		  	)^#13:filter#`,
 	},
+	{
+		I: `m.filter(__result__, false)`,
+		E: `ERROR: <input>:1:10: iteration variable overwrites accumulator variable
+             | m.filter(__result__, false)
+             | .........^`,
+	},
+	{
+		I: `m.filter(a.b, false)`,
+		E: `ERROR: <input>:1:11: argument is not an identifier
+             | m.filter(a.b, false)
+             | ..........^`,
+	},
 
 	// Tests from C++ parser
 	{