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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
}
}
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