fmt: fix removal of selective imported Enum (#10729)

vlib/v/fmt/fmt.v

@@ -1804,6 +1804,7 @@ pub fn (mut f Fmt) dump_expr(node ast.DumpExpr) {
 pub fn (mut f Fmt) enum_val(node ast.EnumVal) {
 	name := f.short_module(node.enum_name)
 	f.write(name + '.' + node.val)
+	f.mark_import_as_used(name)
 }
 
 pub fn (mut f Fmt) ident(node ast.Ident) {

vlib/v/fmt/tests/import_selective_expected.vv

@@ -6,6 +6,7 @@ import os {
 	user_os,
 }
 import mod {
+	Enum,
 	FnArg,
 	FnRet,
 	InterfaceField,
@@ -40,6 +41,8 @@ fn f(v FnArg) FnRet {
 	}
 	_ = v as RightOfAs
 
+	println(Enum.val)
+
 	return {}
 }
 

vlib/v/fmt/tests/import_selective_input.vv

@@ -22,6 +22,8 @@ import mod {
 
 	RightOfIs,
 	RightOfAs,
+
+	Enum
 }
 
 struct Struct {
@@ -43,6 +45,8 @@ fn f(v FnArg) FnRet {
 	if v is RightOfIs {}
 	_ = v as RightOfAs
 
+	println(Enum.val)
+
 	return {}
 }