scanner: fix new string interpolation println('{a}{b}{c}{d}') (#16258)

cmd/tools/vtest-cleancode.v

@@ -47,6 +47,7 @@ const verify_known_failing_exceptions = [
 	'vlib/builtin/int_test.v' /* special number formatting that should be tested */,
 	// TODOs and unfixed vfmt bugs
 	'vlib/v/gen/js/tests/js.v', /* local `hello` fn, gets replaced with module `hello` aliased as `hl` */
+	'vlib/v/tests/string_new_interpolation_test.v', /* new string interpolation */
 ]
 
 const vfmt_verify_list = [

vlib/v/eval/gen/infix_gen.v

@@ -9,7 +9,7 @@ const (
 module eval
 import v.token
 import v.ast
-fn(e Eval)infix_expr(left Object,right Object,op token.Kind,expecting ast.Type)Object{match op{'
+fn(e Eval)infix_expr(left Object,right Object,op token.Kind,expecting ast.Type)Object{ match op{'
 	footer = "else{ e.error('unknown infix expression: \$op')}}return empty // should e.error before this anyway
 }
 "
@@ -37,26 +37,26 @@ fn main() {
 	b.write_string(header)
 
 	for enm, op in comparison {
-		b.write_string('.$enm{match left{')
+		b.write_string('.$enm{ match left{')
 		for ct in compound_types {
-			b.write_string('$ct {match right{')
+			b.write_string('$ct { match right{')
 			for ct2 in compound_types {
-				b.write_string('$ct2{return left.val${op}right.val}')
+				b.write_string('$ct2{ return left.val${op}right.val}')
 			}
 			for lt2 in literal_types {
-				b.write_string('$lt2{return left.val${op}right}')
+				b.write_string('$lt2{ return left.val${op}right}')
 			}
 			b.write_string("else{ e.error('invalid operands to $op: $ct and \$right.type_name()')}}}")
 		}
 		for lt in literal_types {
-			b.write_string('$lt {match right{')
+			b.write_string('$lt { match right{')
 			for ct2 in compound_types {
-				b.write_string('$ct2{return left${op}right.val}')
+				b.write_string('$ct2{ return left${op}right.val}')
 			}
 			for lt2 in literal_types {
-				b.write_string('$lt2{return left${op}right}')
+				b.write_string('$lt2{ return left${op}right}')
 			}
-			b.write_string("else {e.error('invalid operands to $op: ")
+			b.write_string("else { e.error('invalid operands to $op: ")
 			b.write_string(if lt == 'i64' { 'int' } else { 'float' })
 			b.write_string(" literal and \$right.type_name()')}}}")
 		}
@@ -66,12 +66,12 @@ fn main() {
 		b.write_string("else { e.error('invalid operands to $op: \$left.type_name() and \$right.type_name()')}}}")
 	}
 	for math, op in math_ops {
-		b.write_string('.$math{match left{')
+		b.write_string('.$math{ match left{')
 		for ct in compound_types {
 			if op in ['<<', '>>'] && ct == 'Float' {
 				continue
 			}
-			b.write_string('$ct {match right{')
+			b.write_string('$ct { match right{')
 			for ct2 in compound_types {
 				if op in ['<<', '>>'] && ct2 == 'Float' {
 					continue
@@ -117,13 +117,13 @@ fn main() {
 					continue
 				}
 				unsafe_start, unsafe_end := if op in ['<<', '>>'] { 'unsafe{', '}' } else { '', '' }
-				b.write_string('$lt2{if expecting in ast.signed_integer_type_idxs{ return Int{ i64(left)${op}i64(right),i8(e.type_to_size(expecting))}}else if expecting in ast.unsigned_integer_type_idxs{ return Uint{ u64(left)${op}u64(right),i8(e.type_to_size(expecting))}}else if expecting==ast.int_literal_type_idx{${unsafe_start}return i64(i64(left)${op}i64(right))$unsafe_end}')
+				b.write_string('$lt2{ if expecting in ast.signed_integer_type_idxs{ return Int{ i64(left)${op}i64(right),i8(e.type_to_size(expecting))}}else if expecting in ast.unsigned_integer_type_idxs{ return Uint{ u64(left)${op}u64(right),i8(e.type_to_size(expecting))}}else if expecting==ast.int_literal_type_idx{${unsafe_start}return i64(i64(left)${op}i64(right))$unsafe_end}')
 				if op !in ['<<', '>>'] {
 					b.write_string('else if expecting in ast.float_type_idxs{ return Float{ f64(left)${op}f64(right), i8(e.type_to_size(expecting))}}else if expecting==ast.float_literal_type_idx{ return f64(f64(left)${op}f64(right))}')
 				}
 				b.write_string(uk_expect_footer)
 			}
-			b.write_string("else {e.error('invalid operands to $op: ")
+			b.write_string("else { e.error('invalid operands to $op: ")
 			b.write_string(if lt == 'i64' { 'int' } else { 'float' })
 			b.write_string(" literal and \$right.type_name()')}}}")
 		}

vlib/v/scanner/scanner.v

@@ -1214,7 +1214,7 @@ fn (mut s Scanner) ident_string() string {
 				u_escapes_pos << s.pos - 1
 			}
 		}
-		// ${var} (ignore in vfmt mode) (skip \$)
+		// '${var}' (ignore in vfmt mode) (skip \$)
 		if prevc == `$` && c == `{` && !is_raw
 			&& s.count_symbol_before(s.pos - 2, scanner.backslash) % 2 == 0 {
 			s.is_inside_string = true
@@ -1223,7 +1223,7 @@ fn (mut s Scanner) ident_string() string {
 			s.pos -= 2
 			break
 		}
-		// $var
+		// '$var'
 		if prevc == `$` && util.is_name_char(c) && !is_raw
 			&& s.count_symbol_before(s.pos - 2, scanner.backslash) % 2 == 0 {
 			s.is_inside_string = true
@@ -1231,7 +1231,7 @@ fn (mut s Scanner) ident_string() string {
 			s.pos -= 2
 			break
 		}
-		// {var} (ignore in vfmt mode) (skip \{)
+		// '{var}' (ignore in vfmt mode) (skip \{)
 		if c == `{` && util.is_name_char(s.text[s.pos + 1]) && prevc != `$` && !is_raw
 			&& s.count_symbol_before(s.pos - 1, scanner.backslash) % 2 == 0 {
 			// Detect certain strings with "{" that are not interpolation:
@@ -1258,6 +1258,33 @@ fn (mut s Scanner) ident_string() string {
 				break
 			}
 		}
+		// '{var1}{var2}'
+		if prevc == `{` && util.is_name_char(c) && s.text[s.pos - 2] !in [`$`, `{`] && !is_raw
+			&& s.count_symbol_before(s.pos - 2, scanner.backslash) % 2 == 0 {
+			// Detect certain strings with "{" that are not interpolation:
+			// e.g. "{init: " (no "}" at the end)
+			mut is_valid_inter := true
+			for i := s.pos; i < s.text.len; i++ {
+				if s.text[i] == `}` {
+					// No } in this string, so it's not a valid `{x}` interpolation
+					break
+				}
+				if s.text[i] in [`=`, `:`, `\n`, s.inter_quote] {
+					// We reached the end of the line or string without reaching "}".
+					// Also if there's "=", there's no way it's a valid interpolation expression:
+					// e.g. `println("{a.b = 42}")` `println('{foo:bar}')`
+					is_valid_inter = false
+					break
+				}
+			}
+			if is_valid_inter {
+				s.is_inside_string = true
+				s.is_enclosed_inter = true
+				// so that s.pos points to $ at the next step
+				s.pos -= 2
+				break
+			}
+		}
 		if c != scanner.backslash {
 			backslash_count = 0
 		}

vlib/v/tests/string_new_interpolation_test.v

@@ -0,0 +1,9 @@
+fn test_string_new_interpolation() {
+	a, b, c, d := 1, 2, 3, 4
+
+	println('{a}{b}{c}{d}')
+	assert '{a}{b}{c}{d}' == '1234'
+
+	println('{a} {b} {c} {d}')
+	assert '{a} {b} {c} {d}' == '1 2 3 4'
+}