function values as comptime params

examples/programs/comptime_v1/main.bro

@@ -9,6 +9,10 @@ Point :: struct {
 	y i32
 }
 
+Callback_Config :: struct {
+	call @func(value i32) i32
+}
+
 Box :: union(enum) {
 	point Point
 	empty void
@@ -78,6 +82,26 @@ increment func(value i32) i32 {
 	return value + 1
 }
 
+double func(value i32) i32 {
+	return value * 2
+}
+
+decrement_c c_func(value i32) i32 {
+	return value - 1
+}
+
+apply_comptime func($callback @func(value i32) i32, value i32) i32 {
+	return callback(value)
+}
+
+apply_comptime_c func($callback *c_func(value i32) i32, value i32) i32 {
+	return callback(value)
+}
+
+apply_comptime_config func($config Callback_Config, value i32) i32 {
+	return config.call(value)
+}
+
 call_native func(callback @func(value i32) i32, value i32) i32 {
 	return callback(value)
 }
@@ -180,6 +204,10 @@ main func() i32 {
 	recovered i32 :: $recover()
 	storage i32 :: $storage_mutation()
 	called i32 :: $call_native(increment, 11)
+	comptime_callback i32 :: $apply_comptime(increment, 12)
+	comptime_literal i32 :: $apply_comptime(func(value i32) i32 { return value + 2 }, 12)
+	comptime_c_callback i32 :: $apply_comptime_c(decrement_c, 15)
+	comptime_config i32 :: $apply_comptime_config(Callback_Config {call = increment}, 15)
 	fallible_ok i32 :: $call_fallible(may_fail, false) catch 0
 	fallible_err i32 :: $call_fallible(may_fail, true) catch |e| {
 		result i32 :: match e {
@@ -239,5 +267,20 @@ main func() i32 {
 	if ERRDEFER != 42 {
 		return 17
 	}
+	if comptime_callback != 13 or comptime_literal != 14 or
+	   comptime_c_callback != 14 or comptime_config != 16 {
+		return 18
+	}
+	if apply_comptime(increment, 20) != 21 or apply_comptime(increment, 21) != 22 or
+	   apply_comptime(double, 20) != 40 {
+		return 19
+	}
+	if apply_comptime(func(value i32) i32 { return value + 3 }, 20) != 23 {
+		return 20
+	}
+	if apply_comptime_c(decrement_c, 20) != 19 or
+	   apply_comptime_config(Callback_Config {call = increment}, 20) != 21 {
+		return 21
+	}
 	return 0
 }