Matteo Scandolo | a6a3aee | 2019-11-26 13:30:14 -0700 | [diff] [blame] | 1 | // Copyright 2017, The Go Authors. All rights reserved. |
| 2 | // Use of this source code is governed by a BSD-style |
| 3 | // license that can be found in the LICENSE.md file. |
| 4 | |
| 5 | // Package function identifies function types. |
| 6 | package function |
| 7 | |
| 8 | import "reflect" |
| 9 | |
| 10 | type funcType int |
| 11 | |
| 12 | const ( |
| 13 | _ funcType = iota |
| 14 | |
| 15 | ttbFunc // func(T, T) bool |
| 16 | tibFunc // func(T, I) bool |
| 17 | trFunc // func(T) R |
| 18 | |
| 19 | Equal = ttbFunc // func(T, T) bool |
| 20 | EqualAssignable = tibFunc // func(T, I) bool; encapsulates func(T, T) bool |
| 21 | Transformer = trFunc // func(T) R |
| 22 | ValueFilter = ttbFunc // func(T, T) bool |
| 23 | Less = ttbFunc // func(T, T) bool |
| 24 | ) |
| 25 | |
| 26 | var boolType = reflect.TypeOf(true) |
| 27 | |
| 28 | // IsType reports whether the reflect.Type is of the specified function type. |
| 29 | func IsType(t reflect.Type, ft funcType) bool { |
| 30 | if t == nil || t.Kind() != reflect.Func || t.IsVariadic() { |
| 31 | return false |
| 32 | } |
| 33 | ni, no := t.NumIn(), t.NumOut() |
| 34 | switch ft { |
| 35 | case ttbFunc: // func(T, T) bool |
| 36 | if ni == 2 && no == 1 && t.In(0) == t.In(1) && t.Out(0) == boolType { |
| 37 | return true |
| 38 | } |
| 39 | case tibFunc: // func(T, I) bool |
| 40 | if ni == 2 && no == 1 && t.In(0).AssignableTo(t.In(1)) && t.Out(0) == boolType { |
| 41 | return true |
| 42 | } |
| 43 | case trFunc: // func(T) R |
| 44 | if ni == 1 && no == 1 { |
| 45 | return true |
| 46 | } |
| 47 | } |
| 48 | return false |
| 49 | } |