line, isPrefix, err := b.ReadLine()
		if !bytes.Equal(line, e.line) {
			t.Errorf("%q call %d, line == %q, want %q", input, i, line, e.line)
			return
		}
		if isPrefix != e.isPrefix {
			t.Errorf("%q call %d, isPrefix == %v, want %v", input, i, isPrefix, e.isPrefix)
			return
		}
		if err != e.err {
			t.Errorf("%q call %d, err == %v, want %v", input, i, err, e.err)
			return
		}
	}
}

func (p *Package) rewriteCalls(f *File) bool {
	needsUnsafe := false
	// Walk backward so that in C.f1(C.f2()) we rewrite C.f2 first.
	for _, call := range f.Calls {
		if call.Done {
			continue
		}
		start := f.offset(call.Call.Pos())
		end := f.offset(call.Call.End())
		str, nu := p.rewriteCall(f, call)
		if str != "" {
			f.Edit.Replace(start, end, str)
			if nu {
				needsUnsafe = true
			}
		}
	}