cgen: fix array of fns index call with embeded array index (fix #17381) (#22198)

Author: yuyi98

vlib/v/gen/c/index.v

@@ -234,6 +234,7 @@ fn (mut g Gen) index_of_array(node ast.IndexExpr, sym ast.TypeSymbol) {
 		}
 	} else {
 		is_direct_array_access := g.is_direct_array_access || node.is_direct
+		is_fn_index_call := g.is_fn_index_call && elem_sym.info is ast.FnType
 		// do not clone inside `opt_ok(opt_ok(&(string[]) {..})` before returns
 		needs_clone := info.elem_type == ast.string_type_idx && g.is_autofree && !(g.inside_return
 			&& g.fn_decl != unsafe { nil } && g.fn_decl.return_type.has_flag(.option))
@@ -257,7 +258,7 @@ fn (mut g Gen) index_of_array(node ast.IndexExpr, sym ast.TypeSymbol) {
 			if needs_clone {
 				g.write('/*2*/string_clone(')
 			}
-			if g.is_fn_index_call {
+			if is_fn_index_call {
 				if elem_sym.info is ast.FnType {
 					g.write('((')
 					g.write_fn_ptr_decl(&elem_sym.info, '')
@@ -297,13 +298,13 @@ fn (mut g Gen) index_of_array(node ast.IndexExpr, sym ast.TypeSymbol) {
 			g.write('data)[')
 			g.expr(node.index)
 			g.write(']')
-			if g.is_fn_index_call {
+			if is_fn_index_call {
 				g.write(')')
 			}
 		} else {
 			g.write(', ')
 			g.expr(node.index)
-			if g.is_fn_index_call {
+			if is_fn_index_call {
 				g.write(')))')
 			} else {
 				g.write('))')

vlib/v/tests/builtin_arrays/array_of_fns_index_call_with_embeded_array_call_test.v

@@ -0,0 +1,64 @@
+fn max_speed(functions []fn (int) int, g fn (int) int, end_time int) int {
+	mut s := [0]
+	mut gears := []int{len: end_time, init: 0}
+
+	for t in 0 .. end_time {
+		stay_in_gear_speed := if t - 1 >= 0 { functions[gears[t - 1]](s[t - 1]) } else { 0 }
+		shift_gear_speed := if t - 2 >= 0 { functions[gears[t - 2] + 1](g(s[t - 2])) } else { 0 }
+		if stay_in_gear_speed > shift_gear_speed {
+			gears[t] = if t - 1 >= 0 { gears[t - 1] } else { 0 }
+			s << stay_in_gear_speed
+		} else {
+			gears[t] = if t - 2 >= 0 { gears[t - 2] } else { 0 } + 1
+			s << shift_gear_speed
+		}
+	}
+	return s[end_time]
+}
+
+@[direct_array_access]
+fn max_speed_direct_access(functions []fn (int) int, g fn (int) int, end_time int) int {
+	mut s := [0]
+	mut gears := []int{len: end_time, init: 0}
+
+	for t in 0 .. end_time {
+		stay_in_gear_speed := if t - 1 >= 0 { functions[gears[t - 1]](s[t - 1]) } else { 0 }
+		shift_gear_speed := if t - 2 >= 0 { functions[gears[t - 2] + 1](g(s[t - 2])) } else { 0 }
+		if stay_in_gear_speed > shift_gear_speed {
+			gears[t] = if t - 1 >= 0 { gears[t - 1] } else { 0 }
+			s << stay_in_gear_speed
+		} else {
+			gears[t] = if t - 2 >= 0 { gears[t - 2] } else { 0 } + 1
+			s << shift_gear_speed
+		}
+	}
+	return s[end_time]
+}
+
+fn first_gear(speed int) int {
+	return speed + 1
+}
+
+fn second_gear(speed int) int {
+	return speed + 1
+}
+
+fn third_gear(speed int) int {
+	return speed + 1
+}
+
+fn decelerate(speed int) int {
+	return speed - 3
+}
+
+fn test_array_of_fns_index_call_with_embeded_array_call() {
+	funcs := [first_gear, second_gear, third_gear]
+
+	speed1 := max_speed(funcs, decelerate, 3)
+	println(speed1)
+	assert speed1 == 1
+
+	speed2 := max_speed_direct_access(funcs, decelerate, 3)
+	println(speed2)
+	assert speed2 == 1
+}