optimize a in [1,2,3] to a == 1 || a == 2 || a == 3

compiler/optimization.v

@@ -0,0 +1,40 @@
+module main
+
+// `a in [1,2,3]` => `a == 1 || a == 2 || a == 3`
+// avoid allocation
+// `typ` is the type of `a`
+// `ph` is for string_eq()
+fn (p mut Parser) in_optimization(typ string, ph int) {
+	p.check(.lsbr)
+	mut i := 0
+	// Get `a` expr value (can be a string literal, not a variable)
+	expr := p.cgen.cur_line.right(ph)
+	is_str := typ == 'string'
+	//println('!! $p.expr_var.name => $name ($typ)')
+	for p.tok != .rsbr && p.tok != .eof {
+		if i > 0 {
+			if is_str {
+				p.gen(' || string_eq($expr, ')
+			}	else {
+				p.gen(' || $expr == ')
+			}
+		}	
+		if i == 0 {
+			if is_str {
+				p.cgen.set_placeholder(ph, ' string_eq(')
+				p.gen(', ')
+			} else {
+				p.gen(' ==')
+			}	
+		}	
+		p.check_types(p.bool_expression(), typ)
+		if is_str {
+			p.gen(')')
+		}	
+		if p.tok != .rsbr {
+			p.check(.comma)
+		}
+		i++
+	}	
+	p.check(.rsbr)
+}

compiler/parser.v

@@ -2322,7 +2322,6 @@ fn (p mut Parser) index_expr(typ_ string, fn_ph int) string {
 		}
 	}
 	// TODO move this from index_expr()
-	// TODO if p.tok in ...
 	if (p.tok == .assign && !p.is_sql) || p.tok.is_assign() {
 		if is_indexer && is_str && !p.builtin_mod {
 			p.error('strings are immutable')
@@ -2377,6 +2376,13 @@ fn (p mut Parser) indot_expr() string {
 	if p.tok == .key_in {
 		p.fgen(' ')
 		p.check(.key_in)
+		//if p.pref.is_debug && p.tok == .lsbr {
+		if p.tok == .lsbr {
+			// a in [1,2,3] optimization => `a == 1 || a == 2 || a == 3`
+			// avoids an allocation
+			p.in_optimization(typ, ph)
+			return 'bool'
+		}	
 		p.fgen(' ')
 		p.gen('), ')
 		arr_typ := p.expression()

vlib/builtin/array_test.v

@@ -287,3 +287,12 @@ fn test_multi() {
 	//b :=  [ [[1,2,3],[4,5,6]], [[1,2]] ]
 	//assert b[0][0][0] == 1
 }	
+
+fn test_in() {
+	a := [1,2,3]
+	assert 1 in a
+	assert 2 in a
+	assert 3 in a
+	assert !(4 in a)
+	assert !(0 in a)
+}	

vlib/builtin/string.v

@@ -629,12 +629,8 @@ pub fn (a []string) to_c() voidptr {
 }
 */
 
-fn is_space(c byte) bool {
-	return c in [` `,`\n`,`\t`,`\v`,`\f`,`\r`]
-}
-
 pub fn (c byte) is_space() bool {
-	return is_space(c)
+	return c in [` `,`\n`,`\t`,`\v`,`\f`,`\r`]
 }
 
 pub fn (s string) trim_space() string {