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| author | Robert Griesemer <gri@golang.org> | 2021-04-27 18:05:20 -0700 |
|---|---|---|
| committer | Robert Griesemer <gri@golang.org> | 2021-04-28 18:50:51 +0000 |
| commit | 764f53eb6ccc55ad52ddfeed47485de76f4453bb (patch) | |
| tree | 33a6e5816fadec692d3d579271c23be36890a9a5 /doc | |
| parent | 42812a2feec29873aa6ee594d1355948e78e92a3 (diff) | |
| download | go-764f53eb6ccc55ad52ddfeed47485de76f4453bb.tar.gz go-764f53eb6ccc55ad52ddfeed47485de76f4453bb.zip | |
spec: clarify conditions for switch expression type
1. The existing prose implied that a switch expression type must
be comparable because it is tested for equality against all case
expressions. But for an empty switch (no case expressions), it
was not clear if the switch expression needed to be comparable.
Require it to match the behavior of compiler and type checkers.
2. While making this change, remove redundant language explaining
what happens with untyped boolean switch expression values: the
default type of an untyped boolean value is bool, this is already
covered by the first part of the relevant sentence.
Fixes #43200.
Change-Id: Id8e0f29cfa8722b57cd2b7b58cba85b58c5f842b
Reviewed-on: https://go-review.googlesource.com/c/go/+/314411
Trust: Robert Griesemer <gri@golang.org>
Reviewed-by: Matthew Dempsky <mdempsky@google.com>
Reviewed-by: Rob Pike <r@golang.org>
Diffstat (limited to 'doc')
| -rw-r--r-- | doc/go_spec.html | 6 |
1 files changed, 3 insertions, 3 deletions
diff --git a/doc/go_spec.html b/doc/go_spec.html index 95bf7d30f8b..e59b3554f28 100644 --- a/doc/go_spec.html +++ b/doc/go_spec.html @@ -1,6 +1,6 @@ <!--{ "Title": "The Go Programming Language Specification", - "Subtitle": "Version of Apr 21, 2021", + "Subtitle": "Version of Apr 28, 2021", "Path": "/ref/spec" }--> @@ -4953,9 +4953,9 @@ ExprSwitchCase = "case" ExpressionList | "default" . <p> If the switch expression evaluates to an untyped constant, it is first implicitly -<a href="#Conversions">converted</a> to its <a href="#Constants">default type</a>; -if it is an untyped boolean value, it is first implicitly converted to type <code>bool</code>. +<a href="#Conversions">converted</a> to its <a href="#Constants">default type</a>. The predeclared untyped value <code>nil</code> cannot be used as a switch expression. +The switch expression type must be <a href="#Comparison_operators">comparable</a>. </p> <p> |