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cmd/stringer: remove redundant check in generated code

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In a certain case, stringer would generate the following check for an
an unsigned integer i: "0 <= i". This changes stringer to not generate
such a check.

Also adds an additional test case for an unsigned multiple run that does
not include zero. There was already a case ("unum") that included an
unsigned multiple run starting at zero. This case's output was updated
accordingly.

Fixes golang/go#36461

Change-Id: I57e79384a0b802fa4571e2b3495db168b814bcaa
Reviewed-on: https://go-review.googlesource.com/c/tools/+/214180
Run-TryBot: Daniel Martí <mvdan@mvdan.cc>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Daniel Martí <mvdan@mvdan.cc>
This commit is contained in:
Adam Williams 2020-01-09 17:08:47 -07:00 committed by Daniel Martí
parent 3b9e235283
commit 9dc88fb721
2 changed files with 57 additions and 2 deletions
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52
cmd/stringer/golden_test.go
View File

@ -34,6 +34,7 @@ var golden = []Golden{
{"gap", "", false, gap_in, gap_out},
{"num", "", false, num_in, num_out},
{"unum", "", false, unum_in, unum_out},
{"unumpos", "", false, unumpos_in, unumpos_out},
{"prime", "", false, prime_in, prime_out},
{"prefix", "Type", false, prefix_in, prefix_out},
{"tokens", "", true, tokens_in, tokens_out},
@ -240,7 +241,7 @@ var (
func (i Unum) String() string {
switch {
case 0 <= i && i <= 2:
case i <= 2:
return _Unum_name_0[_Unum_index_0[i]:_Unum_index_0[i+1]]
case 253 <= i && i <= 254:
i -= 253
@ -251,6 +252,55 @@ func (i Unum) String() string {
}
`
// Unsigned positive integers.
const unumpos_in = `type Unumpos uint
const (
m253 Unumpos = iota + 253
m254
)
const (
m1 Unumpos = iota + 1
m2
m3
)
`
const unumpos_out = `func _() {
// An "invalid array index" compiler error signifies that the constant values have changed.
// Re-run the stringer command to generate them again.
var x [1]struct{}
_ = x[m253-253]
_ = x[m254-254]
_ = x[m1-1]
_ = x[m2-2]
_ = x[m3-3]
}
const (
_Unumpos_name_0 = "m1m2m3"
_Unumpos_name_1 = "m253m254"
)
var (
_Unumpos_index_0 = [...]uint8{0, 2, 4, 6}
_Unumpos_index_1 = [...]uint8{0, 4, 8}
)
func (i Unumpos) String() string {
switch {
case 1 <= i && i <= 3:
i -= 1
return _Unumpos_name_0[_Unumpos_index_0[i]:_Unumpos_index_0[i+1]]
case 253 <= i && i <= 254:
i -= 253
return _Unumpos_name_1[_Unumpos_index_1[i]:_Unumpos_index_1[i+1]]
default:
return "Unumpos(" + strconv.FormatInt(int64(i), 10) + ")"
}
}
`
// Enough gaps to trigger a map implementation of the method.
// Also includes a duplicate to test that it doesn't cause problems
const prime_in = `type Prime int

7
cmd/stringer/stringer.go
View File

@ -610,7 +610,12 @@ func (g *Generator) buildMultipleRuns(runs [][]Value, typeName string) {
g.Printf("\t\treturn _%s_name_%d\n", typeName, i)
continue
}
g.Printf("\tcase %s <= i && i <= %s:\n", &values[0], &values[len(values)-1])
if values[0].value == 0 && !values[0].signed {
// For an unsigned lower bound of 0, "0 <= i" would be redundant.
g.Printf("\tcase i <= %s:\n", &values[len(values)-1])
} else {
g.Printf("\tcase %s <= i && i <= %s:\n", &values[0], &values[len(values)-1])
}
if values[0].value != 0 {
g.Printf("\t\ti -= %s\n", &values[0])
}