fmt: force conversion of []Type{init: it} -> []Type{init: index} (#26201)

Author: kbkpbot

vlib/v/fmt/fmt.v

@@ -47,6 +47,7 @@ pub mut:
 	is_index_expr            bool
 	is_mbranch_expr          bool // match a { x...y { } }
 	is_struct_init           bool
+	is_array_init            bool
 	fn_scope                 &ast.Scope = unsafe { nil }
 	wsinfix_depth            int
 	format_state             FormatState
@@ -1839,7 +1840,10 @@ pub fn (mut f Fmt) array_init(node ast.ArrayInit) {
 		}
 		if node.has_init {
 			f.write('init: ')
+			old_is_array_init := f.is_array_init
+			f.is_array_init = true
 			f.expr(node.init_expr)
+			f.is_array_init = old_is_array_init
 		}
 		f.write('}')
 		return
@@ -2358,6 +2362,8 @@ pub fn (mut f Fmt) ident(node ast.Ident) {
 		name := f.short_module(node.name)
 		if node.name.contains('__static__') {
 			f.write_static_method(node.name, name)
+		} else if f.is_array_init && name == 'it' {
+			f.write('index')
 		} else {
 			f.write(name)
 		}

vlib/v/fmt/tests/array_init_it_expected.vv

@@ -0,0 +1 @@
+println([]int{len: 10, init: index + 2})

vlib/v/fmt/tests/array_init_it_input.vv

@@ -0,0 +1 @@
+println([]int{len: 10, init: it + 2})

vlib/v/gen/js/tests/array.v

@@ -22,9 +22,9 @@ fn main() {
 
 	// index initializations
 	list1 := []string{len: 3, init: 'Item ${index}'}
-	list2 := []string{len: 3, init: 'Item ${it}'}
+	list2 := []string{len: 3, init: 'Item ${index}'}
 	list3 := []int{len: 3, init: index}
-	list4 := []string{len: 4, init: '${index}:${it * 2}'}
+	list4 := []string{len: 4, init: '${index}:${index * 2}'}
 	println(list1)
 	println(list2)
 	println(list1 == list2)