design/19308-number-literals: add note about gofmt
Add note about lowercasing base prefixes and exponents in gofmt.
See also golang.org/cl/160184.
For golang/go#19308.
For golang/go#12711.
For golang/go#29008.
Change-Id: I79f813badc0b28147fba40072d9c7436bfa91aaa
Reviewed-on: https://go-review.googlesource.com/c/160478
Run-TryBot: Russ Cox <rsc@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
Reviewed-by: Robert Griesemer <gri@golang.org>
diff --git a/design/19308-number-literals.md b/design/19308-number-literals.md
index 3375a48..69f02f0 100644
--- a/design/19308-number-literals.md
+++ b/design/19308-number-literals.md
@@ -448,6 +448,22 @@
and
[`text/template`](https://golang.org/pkg/html/template/).
+### Tool Changes
+
+Gofmt will understand the new syntax once
+[`go/scanner`](https://golang.org/pkg/go/scanner/)
+is updated.
+For legibility,
+gofmt will also rewrite capitalized base prefixes `0B`, `0O`, and `0X`
+and exponent prefixes `E` and `P`
+to their lowercase equivalents `0b`, `0o`, `0x`, `e`, and `p`.
+This is especially important for `0O377` vs `0o377`.
+
+To avoid introducing incompatibilities into
+otherwise backward-compatible code,
+gofmt will not rewrite `0377` to `0o377`.
+(Perhaps in a few years we will be able to consider doing that.)
+
## Rationale
As discussed in the background section,
@@ -483,7 +499,8 @@
we must keep the existing `0377` syntax in Go 1,
so Go will have two octal integer syntaxes,
like Python 2.7 and non-strict JavaScript.
-After a few years, once there are no supported Go releases
+As noted earlier,
+after a few years, once there are no supported Go releases
missing the `0o377` syntax,
we could consider changing
`gofmt` to at least reformat `0377` to `0o377` for clarity.
