scanner: fix interpolation with string args (#7214)

vlib/v/scanner/scanner.v

@@ -26,6 +26,7 @@ pub mut:
 	is_inside_string            bool
 	is_inter_start              bool // for hacky string interpolation TODO simplify
 	is_inter_end                bool
+	is_enclosed_inter           bool
 	is_debug                    bool
 	line_comment                string
 	// prev_tok                 TokenKind
@@ -34,6 +35,7 @@ pub mut:
 	is_print_colored_error      bool
 	is_print_rel_paths_on_error bool
 	quote                       byte // which quote is used to denote current string: ' or "
+	inter_quote                 byte
 	line_ends                   []int // the positions of source lines ends   (i.e. \n signs)
 	nr_lines                    int // total number of lines in the source file that were scanned
 	is_vh                       bool // Keep newlines
@@ -716,12 +718,14 @@ fn (mut s Scanner) text_scan() token.Token {
 			`}` {
 				// s = `hello $name !`
 				// s = `hello ${name} !`
-				if s.is_inside_string {
+				if s.is_enclosed_inter {
 					s.pos++
 					if s.text[s.pos] == s.quote {
 						s.is_inside_string = false
+						s.is_enclosed_inter = false
 						return s.new_token(.string, '', 1)
 					}
+					s.is_enclosed_inter = false
 					ident_string := s.ident_string()
 					return s.new_token(.string, ident_string, ident_string.len + 2) // + two quotes
 				} else {
@@ -993,15 +997,23 @@ fn (mut s Scanner) ident_string() string {
 	is_quote := q == single_quote || q == double_quote
 	is_raw := is_quote && s.pos > 0 && s.text[s.pos - 1] == `r`
 	is_cstr := is_quote && s.pos > 0 && s.text[s.pos - 1] == `c`
-	if is_quote && !s.is_inside_string {
+	if is_quote {
+		if s.is_inside_string {
+			s.inter_quote = q
+		} else {
 			s.quote = q
 		}
+	}
 	// if s.file_path.contains('string_test') {
 	// println('\nident_string() at char=${s.text[s.pos].str()}')
 	// println('linenr=$s.line_nr quote=  $qquote ${qquote.str()}')
 	// }
 	mut n_cr_chars := 0
 	mut start := s.pos
+	if s.text[start] == s.quote ||
+		(s.text[start] == s.inter_quote && (s.is_inter_start || s.is_enclosed_inter)) {
+		start++
+	}
 	s.is_inside_string = false
 	slash := `\\`
 	for {
@@ -1016,6 +1028,9 @@ fn (mut s Scanner) ident_string() string {
 			// handle '123\\'  slash at the end
 			break
 		}
+		if c == s.inter_quote && (s.is_inter_start || s.is_enclosed_inter) {
+			break
+		}
 		if c == `\r` {
 			n_cr_chars++
 		}
@@ -1054,6 +1069,7 @@ fn (mut s Scanner) ident_string() string {
 		// ${var} (ignore in vfmt mode) (skip \$)
 		if prevc == `$` && c == `{` && !is_raw && s.count_symbol_before(s.pos - 2, slash) % 2 == 0 {
 			s.is_inside_string = true
+			s.is_enclosed_inter = true
 			// so that s.pos points to $ at the next step
 			s.pos -= 2
 			break
@@ -1068,9 +1084,6 @@ fn (mut s Scanner) ident_string() string {
 		}
 	}
 	mut lit := ''
-	if s.text[start] == s.quote {
-		start++
-	}
 	mut end := s.pos
 	if s.is_inside_string {
 		end++

vlib/v/tests/string_interpolation_string_args_test.v

@@ -0,0 +1,9 @@
+fn show_info(a string) string {
+	return a
+}
+
+fn test_interpolation_string_args() {
+	assert '${show_info("abc")}' == 'abc'
+	assert '${show_info("bac")}' == 'bac'
+	assert '${"aaa"}' == 'aaa'
+}