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doc/go1.20: document spec changes

Change-Id: I2e35bddfe20c96a8dc0ab187286aaf543ff66164
Reviewed-on: https://go-review.googlesource.com/c/go/+/452758
Reviewed-by: Robert Griesemer <gri@google.com>
Reviewed-by: Matthew Dempsky <mdempsky@google.com>
Run-TryBot: Russ Cox <rsc@golang.org>
TryBot-Result: Gopher Robot <gobot@golang.org>
This commit is contained in:
Russ Cox 2022-11-22 09:24:24 -05:00
parent a8510f92e6
commit a16f4175b5

View File

@ -26,15 +26,34 @@ Do not send CLs removing the interior tags from such phrases.
<h2 id="language">Changes to the language</h2>
<p>
TODO: complete this section
</p>
<p><!-- https://go.dev/issue/8606 -->
TODO: <a href="https://go.dev/issue/8606">https://go.dev/issue/8606</a>: define that structs are compared field-by-field as listed in source code
Go 1.20 includes three changes to the language.
</p>
<p><!-- https://go.dev/issue/46505 -->
TODO: <a href="https://go.dev/issue/46505">https://go.dev/issue/46505</a>: allow conversion from slice to array
Go 1.17 added <a href="/ref/spec#Conversions_from_slice_to_array_pointer">conversions from slice to an array pointer</a>.
Go 1.20 extends this to allow conversions from a slice to an array:
given a slice <code>x</code>, <code>[4]byte(x)</code> can now be written
instead of <code>*(*[4]byte)(x)</code>.
</p>
<p><!-- https://go.dev/issue/53003 -->
The <a href="/ref/spec/#Package_unsafe"><code>unsafe</code> package</a> defines
three new functions <code>SliceData</code>, <code>String</code>, and <code>StringData</code>.
Along with Go 1.17's <code>Slice</code>, these functions now provide the complete ability to
construct and deconstruct slice and string values, without depending on their exact representation.
</p>
<p><!-- https://go.dev/issue/8606 -->
The specification now defines that struct values are compared one field at a time,
considering fields in the order they appear in the struct type definition,
and stopping at the first mismatch.
The specification could previously have been read as if
all fields needed to be compared beyond the first mismatch.
Similarly, the specification now defines that array values are compared
one element at a time, in increasing index order.
In both cases, the difference affects whether certain comparisons must panic.
Existing programs are unchanged: the new spec wording describes
what the implementations have always done.
</p>
<h2 id="ports">Ports</h2>