goreduce

Reduce a program to its simplest form as long as it produces a compiler error or any output (such as a panic) matching a regular expression.

go get -u mvdan.cc/goreduce

Note that this project isn't being actively developed right now. If you are interested in continuing the work, feel free to fork the repository, or email me to discuss transferring the entire repository over.

Example

func main() {
        a := []int{1, 2, 3}
        if true {
                a = append(a, 4)
        }
        a[1] = -2
        println(a[10])
}

goreduce -match 'index out of range' .

func main() {
        a := []int{}
        println(a[0])
}

For more usage information, see goreduce -h.

Design

• The tool should be reproducible, giving the same output for an input program as long as external factors don't modify its behavior
• The rules should be as simple and composable as possible
• Rules should avoid generating changes that they can know won't compile

Rules

Removing

	Before	After
statement	a; b	a or b
index	a[1]	a
slice	a[:2]	a or a[:]
binary part	a + b, a && b	a or b
unary op	-a, !a	a
star	*a	a
parentheses	(a)	a
if/else	if a { b } else c	b or c
defer	defer f()	f()
go	go f()	f()
basic value	123, "foo"	0, ""
composite value	T{a, b}	T{}

Inlining

	Before	After
const	const c = 0; f(c)	f(0)
var	v := false; f(v)	f(false)
case	case x: a	a
block	{ a }	a
simple call	f()	{ body }

Resolving

	Before	After
integer op	2 * 3	6
string op	"foo" + "bar"	"foobar"
slice	"foo"[1:]	"oo"
index	"foo"[0]	'f'
builtin	len("foo")	3