There is an example for nil slice already, so adding example for non-nil
zero length slice, too, clarifying to the reader that the result is also
non-nil and different from nil slice case.
Updates #395
Change-Id: I019db1b1a1c0c621161ecaaacab5a4d888764b1a
Reviewed-on: https://go-review.googlesource.com/c/go/+/336890
Trust: Cuong Manh Le <cuong.manhle.vn@gmail.com>
Trust: Robert Griesemer <gri@golang.org>
Run-TryBot: Cuong Manh Le <cuong.manhle.vn@gmail.com>
TryBot-Result: Go Bot <gobot@golang.org>
Reviewed-by: Robert Griesemer <gri@golang.org>
For #19367
Change-Id: If0ff8ddba3b6b48e2e198cf3653e73284c7572a3
Reviewed-on: https://go-review.googlesource.com/c/go/+/332409
Trust: Ian Lance Taylor <iant@golang.org>
Reviewed-by: Matthew Dempsky <mdempsky@google.com>
Reviewed-by: Robert Griesemer <gri@golang.org>
Reviewed-by: Keith Randall <khr@golang.org>
Add unsafe.Add and unsafe.Slice to the list of built-in functions
which are not permitted in statement context. The compiler and
type checker already enforce this restriction, this just fixes
a documentation oversight.
For #19367.
For #40481.
Change-Id: Iabc63a8db048eaf40a5f5b5573fdf00b79d54119
Reviewed-on: https://go-review.googlesource.com/c/go/+/329925
Trust: Robert Griesemer <gri@golang.org>
Run-TryBot: Robert Griesemer <gri@golang.org>
Reviewed-by: Matthew Dempsky <mdempsky@google.com>
Reviewed-by: Rob Pike <r@golang.org>
TryBot-Result: Go Bot <gobot@golang.org>
The word "specifier" is used once only here and technically not defined.
Change-Id: Ifc9f0582f4eb3c3011ba60d8008234de511d4be6
Reviewed-on: https://go-review.googlesource.com/c/go/+/323730
Reviewed-by: Robert Griesemer <gri@golang.org>
Trust: Ian Lance Taylor <iant@golang.org>
Trust: Robert Griesemer <gri@golang.org>
Replace "reserved word" by "keyword" as the latter is the official term.
Change-Id: I9f269759b872026034a9f47e4a761cff2d348ca0
Reviewed-on: https://go-review.googlesource.com/c/go/+/323729
Reviewed-by: Robert Griesemer <gri@golang.org>
Trust: Ian Lance Taylor <iant@golang.org>
Trust: Robert Griesemer <gri@golang.org>
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>
In Go1.13 and above, signed integers are permitted as shift counts as long as they are >=0.
However, the comments in the "Arithmetic operators" section says shift operators accept "unsigned integer" as of right operands. Replacing this with "integer>=0" resolves the misunderstanding that shift
operators permit only unsigned integers.
Reference: Go1.13 Release Notes: https://golang.org/doc/go1.13
Change-Id: Icd3c7734d539ab702590e992a618c9251c653c37
GitHub-Last-Rev: 4f263a48d3
GitHub-Pull-Request: golang/go#44664
Reviewed-on: https://go-review.googlesource.com/c/go/+/297249
Reviewed-by: Emmanuel Odeke <emmanuel@orijtech.com>
Reviewed-by: Robert Griesemer <gri@golang.org>
Trust: Emmanuel Odeke <emmanuel@orijtech.com>
Trust: Robert Griesemer <gri@golang.org>
Change-Id: I453d06da2f596eb0b99905aec46a05547d73c62c
Reviewed-on: https://go-review.googlesource.com/c/go/+/290872
Trust: Emmanuel Odeke <emmanuel@orijtech.com>
Trust: Robert Griesemer <gri@golang.org>
Trust: Ian Lance Taylor <iant@golang.org>
Reviewed-by: Robert Griesemer <gri@golang.org>
Reviewed-by: Rob Pike <r@golang.org>
The spec states that a type "may" have a method set associated with it.
Yet every type has a method set, which may be empty. This is clarified
later in the same paragraph. Be clear in the first sentence as well.
Per the suggestion from https://github.com/DQNEO.
Fixes#44318.
Change-Id: I6097b1c7062853e404b7fead56d18a7f9c576fc3
Reviewed-on: https://go-review.googlesource.com/c/go/+/292853
Trust: Robert Griesemer <gri@golang.org>
Run-TryBot: Robert Griesemer <gri@golang.org>
Reviewed-by: Ian Lance Taylor <iant@golang.org>
A caller is not always in a function.
For example, a call can appear in top level declarations.
e.g. var x = f()
Change-Id: I29c4c3b7663249434fb2b8a6d0003267c77268cf
Reviewed-on: https://go-review.googlesource.com/c/go/+/290849
Reviewed-by: Rob Pike <r@golang.org>
Reviewed-by: Ian Lance Taylor <iant@golang.org>
Reviewed-by: Robert Griesemer <gri@golang.org>
Trust: Robert Griesemer <gri@golang.org>
The example, var v, ok T1 = x.(T), can be interpreted as type T1 interface{} or type T = bool; type T1 = T.
Separating the example would help understanding for readers.
Change-Id: I179f4564e67f4d503815d29307df2cebb50c82f9
GitHub-Last-Rev: b34fffb6bb
GitHub-Pull-Request: golang/go#44040
Reviewed-on: https://go-review.googlesource.com/c/go/+/288472
Reviewed-by: Robert Griesemer <gri@golang.org>
Reviewed-by: Rob Pike <r@golang.org>
Reviewed-by: Ian Lance Taylor <iant@golang.org>
Trust: Robert Griesemer <gri@golang.org>
In the current (pre-CL) version of the spec, the 2nd last shift
example appears to be using the array declared in the last example.
On a 32-bit platform, that array would have length 0, which would
lead to a panic in the 2nd last example. Also, if this code were
inside a function, it wouldn't compile (array declared after use).
Use an explicitly declared array for that specific shift example.
Also, split out all cases that produce different results for 32-
vs 64-bit ints.
Fixes#41835.
Change-Id: Ie45114224509e4999197226f91f7f6f934449abb
Reviewed-on: https://go-review.googlesource.com/c/go/+/260398
Trust: Robert Griesemer <gri@golang.org>
Reviewed-by: Russ Cox <rsc@golang.org>
Reviewed-by: Ian Lance Taylor <iant@golang.org>
Suggested by @yaxinlx.
Fixes#41612.
Change-Id: I98b9968a95d090ee3c67ff02678e1874e6d98c33
Reviewed-on: https://go-review.googlesource.com/c/go/+/257159
Trust: Robert Griesemer <gri@golang.org>
Reviewed-by: Rob Pike <r@golang.org>
Reviewed-by: Ian Lance Taylor <iant@golang.org>
The HTML linter 'tidy' reports:
go_spec.html:2556: Warning: unescaped & which should be written as &
go_spec.html:3293: Warning: unescaped & or unknown entity "&s1"
go_spec.html:3293: Warning: unescaped & or unknown entity "&a"
go_spec.html:3294: Warning: unescaped & or unknown entity "&s2"
go_spec.html:3294: Warning: unescaped & or unknown entity "&a"
go_spec.html:2045: Warning: trimming empty <p>
go_spec.html:4526: Warning: trimming empty <ul>
go_spec.html:4533: Warning: trimming empty <ul>
go_spec.html:4539: Warning: trimming empty <ul>
This CL fixes all but the <ul> ones, which I think should be fixed
but are defended by a comment.
Change-Id: I0ca88f5e80755024801877ab1298025ecf8f10c5
Reviewed-on: https://go-review.googlesource.com/c/go/+/214457
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
Reviewed-by: Tobias Klauser <tobias.klauser@gmail.com>
Since the word "regular" has a precise meaning in the context of
formal languages, the Introduction sentence claiming that Go's grammar
is "compact and regular" may mislead readers.
Reword it using Rob's suggestion.
Fixes#36037
Change-Id: I00c1a5714bdab8878d9a77b36d67dae67d63da0f
Reviewed-on: https://go-review.googlesource.com/c/go/+/211277
Reviewed-by: Robert Griesemer <gri@golang.org>
Reviewed-by: Rob Pike <r@golang.org>
In preparation for the forthcoming spec changes for #6977.
While at it, modernize existing File example that dates
back all the way to commit 18c5b488a3.
Change-Id: Id10e4df0513e3de15bd58867222923eefa9473ea
Reviewed-on: https://go-review.googlesource.com/c/go/+/187978
Reviewed-by: Rob Pike <r@golang.org>
Reviewed-by: Matthew Dempsky <mdempsky@google.com>
Reviewed-by: Ian Lance Taylor <iant@golang.org>
The spec was not very precise as to what happens with respect to sharing
if a sliced operand is (a pointer to) an array. Added a small clarification
and a supporting example.
Fixes#31689.
Change-Id: Ic49351bec2033abd3f5428154ec3e9a7c2c9eaa5
Reviewed-on: https://go-review.googlesource.com/c/go/+/177139
Reviewed-by: Matthew Dempsky <mdempsky@google.com>
Reviewed-by: Rob Pike <r@golang.org>
Reviewed-by: Keith Randall <khr@golang.org>
Add a small paragraph and example pointing out
the difference for the case where T is a slice
or map. This is a common error for Go novices.
Fixes#29425.
Change-Id: Icdb59f25361e9f6a09b190fbfcc9ae0c7d90077b
Reviewed-on: https://go-review.googlesource.com/c/go/+/176338
Reviewed-by: Matthew Dempsky <mdempsky@google.com>
The very first paragraph on "Package initialization" stated that
"variables are initialized in declaration order, but after any
variables they might depend on". This phrasing was easily
misread as "declaration order is the first sorting criteria"
and then contradicted what the subsequent paragraphs spelled
out in precise detail.
Instead, variable initialization proceeds by repeatedly determining
a set of ready to initialize variables, and then selecting from that
set the variable declared earliest. That is, declaration order is the
second sorting criteria.
Also, for the purpose of variable initialization, declarations
introducing blank (_) variables are considered like any other
variables (their initialization expressions may have side-effects
and affect initialization order), even though blank identifiers
are not "declared".
This CL adds clarifying language regarding these two issues
and the supporting example.
Both gccgo and go/types implement this behavior. cmd/compile
has a long-standing issue (#22326).
The spec also did not state in which order multiple variables
initialized by a single (multi-value) initialization expression are
handled. This CL adds a clarifying paragraph: If any such variable
is initialized, all that declaration's variables are initialized at
the same time.
This behavior matches user expectation: We are not expecting to
observe partially initialized sets of variables in declarations
such as "var a, b, c = f()".
It also matches existing cmd/compile and go/types (but not gccgo)
behavior.
Finally, cmd/compile, gccgo, and go/types produce different
initialization orders in (esoteric) cases where hidden (not
detected with existing rules) dependencies exist. Added a
sentence and example clarifying how much leeway compilers have
in those situations. The goal is to preserve the ability to
use static initialization while at the same time maintain
the relative initialization order of variables with detected
dependencies.
Fixes #31292.
Updates #22326.
Change-Id: I0a369abff8cfce27afc975998db875f5c580caa2
Reviewed-on: https://go-review.googlesource.com/c/go/+/175980
Reviewed-by: Ian Lance Taylor <iant@golang.org>
Reviewed-by: Matthew Dempsky <mdempsky@google.com>
This CL documents the new binary and octal integer literals,
hexadecimal floats, generalized imaginary literals and digit
separators for all number literals in the spec.
Added empty lines between abutting paragraphs in some places
(a more thorough cleanup can be done in a separate CL).
A minor detail: A single 0 was considered an octal zero per the
syntax (decimal integer literals always started with a non-zero
digit). The new octal literal syntax allows 0o and 0O prefixes
and when keeping the respective octal_lit syntax symmetric with
all the others (binary_lit, hex_lit), a single 0 is not automatically
part of it anymore. Rather than complicating the new octal_lit syntax
to include 0 as before, it is simpler (and more natural) to accept
a single 0 as part of a decimal_lit. This is purely a notational
change.
R=Go1.13
Updates #12711.
Updates #19308.
Updates #28493.
Updates #29008.
Change-Id: Ib9fdc6e781f6031cceeed37aaed9d05c7141adec
Reviewed-on: https://go-review.googlesource.com/c/go/+/161098
Reviewed-by: Rob Pike <r@golang.org>
Reviewed-by: Ian Lance Taylor <iant@golang.org>
This text changed in CL 139099 to add "explicit" in front of "conversion".
But now "explicit conversion or assignment" reads like it might mean
"explicit [conversion or assignment]" when what is meant is
"[explicit conversion] or assignment". To make clear that explicit does
not apply to assignment, use "assignment or explicit conversion".
Change-Id: I8ff7a5b3ecd9f562793502fa6808242f22264f28
Reviewed-on: https://go-review.googlesource.com/c/149340
Reviewed-by: Robert Griesemer <gri@golang.org>
Adjusted spec to explicitly define the string length as the
number of bytes of the string; the prose now matches the prose
for arrays. Made analogous change for slices.
Fixes#28736.
Change-Id: I47cab321c87de0a4c482f5466b819b2cc8993fd1
Reviewed-on: https://go-review.googlesource.com/c/149077
Reviewed-by: Rob Pike <r@golang.org>
Reviewed-by: Matthew Dempsky <mdempsky@google.com>
The spec currently provides a syntactic rule for receiver base types,
and a strict reading of those rules prohibits the use of type aliases
referring to pointer types as receiver types.
This strict interpretation breaks an assumed rule for aliases, which
is that a type literal can always be replaced by an alias denoting
that literal.
Furthermore, cmd/compile always accepted this new formulation of the
receiver type rules and so this change will simply validate what has
been implemented all along.
Fixes#27995.
Change-Id: I032289c926a4f070d6f7795431d86635fe64d907
Reviewed-on: https://go-review.googlesource.com/c/142757
Reviewed-by: Ian Lance Taylor <iant@golang.org>
Reviewed-by: Rob Pike <r@golang.org>
Reviewed-by: Matthew Dempsky <mdempsky@google.com>
The spec used the term "conversion" somewhat indiscriminately for
explicit conversions that appear literally in the source, and implicit
conversions that are implied by the context of an expression.
Be clearer about it by defining the terms.
Also, state that integer to string conversions of the form string(x)
are never implicit. This clarifies situations where implicit conversions
might require an integer to change to a string (but don't and never have
done so). See line 3948.
Fixes#26313.
Change-Id: I8939466df6b5950933ae7c987662ef9f88827fda
Reviewed-on: https://go-review.googlesource.com/c/139099
Reviewed-by: Rob Pike <r@golang.org>
Reviewed-by: Ian Lance Taylor <iant@golang.org>
Fixes#27802.
Change-Id: I7ea9f7279300a55b0cb851893edc591a6f84e324
Reviewed-on: https://go-review.googlesource.com/136758
Reviewed-by: Rob Pike <r@golang.org>
Reviewed-by: Ian Lance Taylor <iant@golang.org>
This reverts commit 4b06d9d727.
Reason for revert: It's a reference to a legendary article
from the Journal of Irreproducible Results.
Updates golang/go#24451
Change-Id: I0288177f4e286bd6ace5774f2e5e0acb02370305
Reviewed-on: https://go-review.googlesource.com/101495
Reviewed-by: Andrew Bonventre <andybons@golang.org>
The fourth example for map indexing states you have a map of type [K]V
and attempts to read in a variable of type T. Further, the example
is meant to showcase the boolean return variable saying whether the
map contained a key, but overrides to type T. This will not compile.
Changed last updated date to February 18
Fixes: #23895
Change-Id: I63c52adbcd989afd4855e329e6c727f4c01f7881
Reviewed-on: https://go-review.googlesource.com/94906
Reviewed-by: Robert Griesemer <gri@golang.org>
The EBNF production
Function = Signature FunctionBody .
was used in FunctionDecl, MethodDecl, and FunctionLit, but only
for the latter it shortened the syntax slightly.
This change "inlines" Function which simplifies FunctionDecl and
MethodDecl and gets rid of the Function production.
This has no impact on the specified language. Also, the Function
production is never referred to by the prose, so it's safe to
remove it from the spec.
Finally, neither go/ast nor go/parser have a representation of
this production via a corresponding node or parse function, so
no possibly valuable documentation is lost, either.
Change-Id: Ia2875d31c6ec2d2079081ef481e50bad4f43c694
Reviewed-on: https://go-review.googlesource.com/91515
Reviewed-by: Matthew Dempsky <mdempsky@google.com>
Reviewed-by: Ian Lance Taylor <iant@golang.org>
Reviewed-by: Rob Pike <r@golang.org>
When we introduced the notion of alias type declarations, we renamed
"named type" to "defined type" to avoid confusion with types denoted
by aliases and thus are also types with names, or "named types".
Some of the old uses of "named types" remained; this change removes
them.
Now the spec consistently uses the terms:
- "defined type" for a type declared via a type definition
- "type name" for any name denoting an (alias or defined) type
- "alias" for a type name declared in an alias declaration
New prose is encouraged to avoid the term "named type" to counter-
act further confusion.
Fixes#23474.
Change-Id: I5fb59f1208baf958da79cf51ed3eb1411cd18e03
Reviewed-on: https://go-review.googlesource.com/89115
Reviewed-by: Rob Pike <r@golang.org>
Fixes#23443.
Change-Id: If60c39b582ee5308e9fa902f93c1b6ae7890346c
Reviewed-on: https://go-review.googlesource.com/87975
Reviewed-by: Ian Lance Taylor <iant@golang.org>
Reviewed-by: Rob Pike <r@golang.org>
Every few months we get a new error report claiming that there
is a typo in the spec related to this specific example. Clearly,
the fact that two types with the same identifier are identical
seems exceedingly obvious to readers; thus the example seems not
worth the trouble. Removing it.
For #9226.
For #22202.
For #22495.
For #23096.
For #23409.
There may be more.
Change-Id: I003ba79dc460ffb028a4ecb5f29efd60f2551912
Reviewed-on: https://go-review.googlesource.com/87417
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
Reviewed-by: Rob Pike <r@golang.org>
Reviewed-by: Ian Lance Taylor <iant@golang.org>
Reviewed-by: Matthew Dempsky <mdempsky@google.com>
