Forbid to redeclare variables, builtins, functions.

checker/checker.go

@@ -875,6 +875,18 @@ func (v *visitor) PointerNode(node *ast.PointerNode) (reflect.Type, info) {
 }
 
 func (v *visitor) VariableDeclaratorNode(node *ast.VariableDeclaratorNode) (reflect.Type, info) {
+	if _, ok := v.config.Types[node.Name]; ok {
+		return v.error(node, "cannot redeclare %v", node.Name)
+	}
+	if _, ok := v.config.Functions[node.Name]; ok {
+		return v.error(node, "cannot redeclare function %v", node.Name)
+	}
+	if _, ok := v.config.Builtins[node.Name]; ok {
+		return v.error(node, "cannot redeclare builtin %v", node.Name)
+	}
+	if _, ok := v.lookupVariable(node.Name); ok {
+		return v.error(node, "cannot redeclare variable %v", node.Name)
+	}
 	vtype, vinfo := v.visit(node.Value)
 	v.scopes = append(v.scopes, scope{node.Name, vtype, vinfo})
 	t, i := v.visit(node.Expr)

checker/checker_test.go

@@ -507,6 +507,26 @@ repeat("0", 1/0)
 cannot use float64 as argument (type int) to call repeat  (1:14)
  | repeat("0", 1/0)
  | .............^
+
+let map = 42; map
+cannot redeclare builtin map (1:5)
+ | let map = 42; map
+ | ....^
+
+let len = 42; len
+cannot redeclare builtin len (1:5)
+ | let len = 42; len
+ | ....^
+
+let Float = 42; Float
+cannot redeclare Float (1:5)
+ | let Float = 42; Float
+ | ....^
+
+let foo = 1; let foo = 2; foo
+cannot redeclare variable foo (1:18)
+ | let foo = 1; let foo = 2; foo
+ | .................^
 `
 
 func TestCheck_error(t *testing.T) {

parser/parser.go

@@ -193,11 +193,13 @@ func (p *parser) parseVariableDeclaration() Node {
 	value := p.parseExpression(0)
 	p.expect(Operator, ";")
 	node := p.parseExpression(0)
-	return &VariableDeclaratorNode{
+	let := &VariableDeclaratorNode{
 		Name:  variableName.Value,
 		Value: value,
 		Expr:  node,
 	}
+	let.SetLocation(variableName.Location)
+	return let
 }
 
 func (p *parser) parseConditional(node Node) Node {