From 108913c69e174ef02827c7701afe9c6708263e7e Mon Sep 17 00:00:00 2001
From: Delyan Angelov <delian66@gmail.com>
Date: Sat, 4 Jul 2020 21:55:14 +0300
Subject: [PATCH] checker: handle error token positions with negative pos.len

---
 vlib/v/checker/checker.v | 5 +++--
 vlib/v/util/errors.v     | 4 ++--
 2 files changed, 5 insertions(+), 4 deletions(-)

diff --git a/vlib/v/checker/checker.v b/vlib/v/checker/checker.v
index dd525cfd6b..2f9c04e354 100644
--- a/vlib/v/checker/checker.v
+++ b/vlib/v/checker/checker.v
@@ -1198,9 +1198,10 @@ pub fn (mut c Checker) call_fn(mut call_expr ast.CallExpr) table.Type {
 				candidate_fn_name := if typ_sym.name.starts_with('anon_') { 'anonymous function' } else { 'fn `$typ_sym.name`' }
 				c.error('cannot use $candidate_fn_name as function type `$arg_typ_sym.str()` in argument ${i+1} to `$fn_name`',
 					call_expr.pos)
+			} else {
+				c.error('cannot use type `$typ_sym.str()` as type `$arg_typ_sym.str()` in argument ${i+1} to `$fn_name`',
+					call_expr.pos)
 			}
-			c.error('cannot use type `$typ_sym.str()` as type `$arg_typ_sym.str()` in argument ${i+1} to `$fn_name`',
-				call_expr.pos)
 		}
 	}
 	if call_expr.generic_type != table.void_type && f.return_type != 0 { // table.t_type {
diff --git a/vlib/v/util/errors.v b/vlib/v/util/errors.v
index 834f4f42db..4228aa10ff 100644
--- a/vlib/v/util/errors.v
+++ b/vlib/v/util/errors.v
@@ -110,8 +110,8 @@ pub fn source_context(kind, source string, column int, pos token.Position) []str
 	tab_spaces := '    '
 	for iline := bline; iline <= aline; iline++ {
 		sline := source_lines[iline]
-		start_column := imin(column, sline.len)
-		end_column := imin(column + pos.len, sline.len)
+		start_column := imax(0, imin(column, sline.len))
+		end_column := imax(0, imin(column + imax(0, pos.len), sline.len))
 		cline := if iline == pos.line_nr {
 			sline[..start_column] + color(kind, sline[start_column..end_column]) + sline[end_column..]
 		} else {