Fix ErrorWithPosition panic when less than two lines

error.go

@@ -124,17 +124,24 @@ func (pe ParseError) ErrorWithPosition() string {
 	if pe.Position.Line > 2 {
 		fmt.Fprintf(b, "% 7d | %s\n", pe.Position.Line-2, expandTab(lines[pe.Position.Line-3]))
 	}
-	if pe.Position.Line > 1 {
-		fmt.Fprintf(b, "% 7d | %s\n", pe.Position.Line-1, expandTab(lines[pe.Position.Line-2]))
-	}
 
 	/// Expand tabs, so that the ^^^s are at the correct position, but leave
 	/// "column 10-13" intact. Adjusting this to the visual column would be
 	/// better, but we don't know the tabsize of the user in their editor, which
 	/// can be 8, 4, 2, or something else. We can't know. So leaving it as the
 	/// character index is probably the "most correct".
-	expanded := expandTab(lines[pe.Position.Line-1])
-	diff := len(expanded) - len(lines[pe.Position.Line-1])
+	var (
+		expanded string
+		diff     int
+	)
+	if pe.Position.Line > 1 {
+		fmt.Fprintf(b, "% 7d | %s\n", pe.Position.Line-1, expandTab(lines[pe.Position.Line-2]))
+		expanded = expandTab(lines[pe.Position.Line-1])
+		diff = len(expanded) - len(lines[pe.Position.Line-1])
+	} else {
+		expanded = expandTab(lines[0])
+		diff = len(expanded) - len(lines[0])
+	}
 
 	fmt.Fprintf(b, "% 7d | %s\n", pe.Position.Line, expanded)
 	fmt.Fprintf(b, "% 10s%s%s\n", "", strings.Repeat(" ", pe.Position.Col-1+diff), strings.Repeat("^", pe.Position.Len))

error_test.go

@@ -245,6 +245,19 @@ func TestParseError(t *testing.T) {
             |         15:04:05.856018510
 			`,
 		},
+
+		{
+			&struct{ String string }{},
+			`string = "test`,
+			`
+            | toml: error: unexpected EOF; expected '"'
+			|
+			| At line 0, column 14:
+			|
+			|       0 | string = "test
+			|                        ^
+			`,
+		},
 	}
 
 	prep := func(s string) string {