parser: snake_case check; array: mutable array test

vlib/builtin/array_test.v

@@ -313,6 +313,27 @@ fn test_mut_slice() {
 	*/
 }
 
+fn double_up(a mut []int) {
+	for i := 0; i < a.len; i++ {
+		a[i] = a[i]*2
+	}
+}
+
+fn double_up_v2(a mut []int) {
+	for i, val in a {
+		a[i] = a[i]*2 // or val*2, doesn't matter
+	}
+}
+
+fn test_mut_arg() {
+	mut arr := [1,2,3,4,5,6,7,8,9,10]
+	double_up(mut arr)
+	assert arr.str() == '[2, 4, 6, 8, 10, 12, 14, 16, 18, 20]'
+	arr = [1,2,3,4,5,6,7,8,9,10]
+	double_up_v2(mut arr)
+	assert arr.str() == '[2, 4, 6, 8, 10, 12, 14, 16, 18, 20]'
+}
+
 fn test_clone() {
 	nums := [1, 2, 3, 4, 100]
 	nums2 := nums.clone()

vlib/v/parser/fn.v

@@ -6,6 +6,7 @@ module parser
 import (
 	v.ast
 	v.table
+	v.scanner
 )
 
 pub fn (p mut Parser) call_expr(is_c bool, mod string) ast.CallExpr {
@@ -103,6 +104,9 @@ fn (p mut Parser) fn_decl() ast.FnDecl {
 	if p.tok.kind == .name {
 		// TODO high order fn
 		name = p.check_name()
+		if !is_c && !p.pref.translated && scanner.contains_capital(name) {
+			p.error('function names cannot contain uppercase letters, use snake_case instead')
+		}
 	}
 	if p.tok.kind in [.plus, .minus, .mul, .div, .mod] {
 		name = p.tok.kind.str() // op_to_fn_name()

vlib/v/util/errors.v

@@ -59,7 +59,7 @@ pub fn formated_error(kind string /*error or warn*/, emsg string, filepath strin
 	mut source_context := ''
 	//
 	final_position := if emanager.support_color {
-		term.bold(term.white(position))
+		term.bold(position) // term.white(position))
 	} else {
 		position
 	}