go-tools/functions/pure.go at 2019.2 · dominikh/go-tools

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package functions

import (

"honnef.co/go/tools/ssa"

)

func filterDebug(instr []ssa.Instruction) []ssa.Instruction {

var out []ssa.Instruction

for _, ins := range instr {

if _, ok := ins.(*ssa.DebugRef); !ok {

out = append(out, ins)

}

return out

}

// IsStub reports whether a function is a stub. A function is

// considered a stub if it has no instructions or exactly one

// instruction, which must be either returning only constant values or

// a panic.

func IsStub(fn *ssa.Function) bool {

if len(fn.Blocks) == 0 {

return true

}

if len(fn.Blocks) > 1 {

return false

}

instrs := filterDebug(fn.Blocks[0].Instrs)

if len(instrs) != 1 {

return false

}

switch instrs[0].(type) {

case *ssa.Return:

// Since this is the only instruction, the return value must

// be a constant. We consider all constants as stubs, not just

// the zero value. This does not, unfortunately, cover zero

// initialised structs, as these cause additional

// instructions.

return true

case *ssa.Panic:

return true

default:

return false

}