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738 Commits

Author SHA1 Message Date
Robert Griesemer
e5ef484691 spec: document range over integer expression
This CL is partly based on CL 510535.

For #61405.

Change-Id: Ic94f6726f9eb34313f11bec7b651921d7e5c18d4
Reviewed-on: https://go-review.googlesource.com/c/go/+/538859
Reviewed-by: Cherry Mui <cherryyz@google.com>
TryBot-Bypass: Robert Griesemer <gri@google.com>
Auto-Submit: Robert Griesemer <gri@google.com>
Reviewed-by: Robert Griesemer <gri@google.com>
2023-11-02 03:57:56 +00:00
Robert Griesemer
aa05674b1d spec: explain eval order of binary operator examples with comments
Fixes #63525.

Change-Id: Ie9aa4dd47c025cd593e576c6e8de1774e1d1e302
Reviewed-on: https://go-review.googlesource.com/c/go/+/535775
Reviewed-by: Robert Griesemer <gri@google.com>
Reviewed-by: Ian Lance Taylor <iant@golang.org>
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Reviewed-by: Keith Randall <khr@golang.org>
Reviewed-by: Keith Randall <khr@google.com>
2023-10-17 15:06:48 +00:00
Matthew Dempsky
856cf23a8a spec: specify evaluation order for binary logical operations
This CL clarifies the order of evaluation of the binary logical
operators, && and ||. The clarified semantics matches what cmd/compile
and x/tools/go/ssa already implement, and prohibit some optimizations
that are arguably allowed today but risk surprising users.

First, it specifies that the left operand is evaluated before the
right operand. This prohibits "(f() || true) && *p" from evaluating
"*p" before "f()".

Second, it specifies that binary logical operations are also ordered
lexically left-to-right with regard to function calls and receive
operations. This prohibits "h(*p || true || f(), g())" from evaluating
"*p" after "g()".

Finally, the "order of evaluation of [...] is not specified" wording
in the example is clarified to acknowledge that there are still some
other orderings that are implied lexically; e.g., x must be evaluated
and indexed before g(), and z now must be evaluated before h(). (Note:
Whether z is evaluated before or after f() remains unspecified, as
there's no lexical dependency.)

Change-Id: I9d316a7f1fbc83be663e116380a2cc7a4ace623d
Reviewed-on: https://go-review.googlesource.com/c/go/+/522938
Reviewed-by: Robert Griesemer <gri@google.com>
Reviewed-by: Ian Lance Taylor <iant@golang.org>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
2023-09-14 05:14:44 +00:00
Matthew Dempsky
ba6fe5172d spec: clarify that []byte("") must be non-nil
The example text below suggests that []byte("") always evaluates to
the non-nil value []byte{}, but the text proper doesn't explicitly
require that. This CL makes it clear that it must not evaluate to
[]byte(nil), which otherwise was allowed by the wording.

Change-Id: I6564bfd5e2fd0c820d9b55d17406221ff93ce80c
Reviewed-on: https://go-review.googlesource.com/c/go/+/521035
Reviewed-by: Robert Griesemer <gri@google.com>
Auto-Submit: Matthew Dempsky <mdempsky@google.com>
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Reviewed-by: Ian Lance Taylor <iant@google.com>
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2023-08-21 23:20:08 +00:00
Ian Lance Taylor
ce16086345 spec: correct type parameter name used in example
Change-Id: I40595a3f598483d029473af465c756f8777ecc91
Reviewed-on: https://go-review.googlesource.com/c/go/+/520915
Reviewed-by: Ian Lance Taylor <iant@google.com>
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2023-08-18 20:44:48 +00:00
Robert Griesemer
ab3332eea9 spec: fix unification rule for inexact interface unification
Irrespective of whether unification is exact or inexact, method
signatures of interfaces must always match exactly: a type never
satisfies/implements an interface if relevant method signatures
are different (i.e., not identical, possibly after substitution).

This change matches the fix https://go.dev/cl/519435.

For #61879.

Change-Id: I28b0a32d32626d85afd32e107efce141235a923d
Reviewed-on: https://go-review.googlesource.com/c/go/+/519455
TryBot-Bypass: Robert Griesemer <gri@google.com>
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2023-08-17 22:56:50 +00:00
Robert Griesemer
976a84b1ff spec: remove unnecessary sentence
Change-Id: I06345199ff16c80be83c345d734caef1714ec089
Reviewed-on: https://go-review.googlesource.com/c/go/+/515338
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2023-08-03 18:56:31 +00:00
cui fliter
3c25d832af doc: fix html tags
Change-Id: I535bec2de8f4f7dd415896a020d71c373c22be56
Reviewed-on: https://go-review.googlesource.com/c/go/+/515155
Run-TryBot: shuang cui <imcusg@gmail.com>
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Reviewed-by: David Chase <drchase@google.com>
2023-08-03 14:43:29 +00:00
Robert Griesemer
03bec7dc6f spec: add Appendix with detailed type unification rules
Change-Id: I0d4ccbc396c48d565c0cbe93c9558ab330a44d02
Reviewed-on: https://go-review.googlesource.com/c/go/+/513275
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2023-07-31 16:39:02 +00:00
Robert Griesemer
7fed33815c spec: update section on type unification for Go 1.21
This leaves the specific unification details out in favor
of a (forthcoming) section in an appendix.

Change-Id: If984c48bdf71c278e1a2759f9a18c51ef58df999
Reviewed-on: https://go-review.googlesource.com/c/go/+/507417
Reviewed-by: Robert Griesemer <gri@google.com>
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2023-07-26 00:02:26 +00:00
Robert Griesemer
3bb51a6805 spec: fix a couple of minor mistakes in type inference section
Change-Id: I9cdb301163b67add39928c8fc7df2b7f3893f45e
Reviewed-on: https://go-review.googlesource.com/c/go/+/511836
Reviewed-by: Ian Lance Taylor <iant@google.com>
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2023-07-21 16:52:52 +00:00
Robert Griesemer
a04a665a92 spec: update section on type inference for Go 1.21
The new section describes type inference as the problem
of solving a set of type equations for bound type parameters.

The next CL will update the section on unification to match
the new inference approach.

Change-Id: I2cb49bfb588ccc82d645343034096a82b7d602e2
Reviewed-on: https://go-review.googlesource.com/c/go/+/503920
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2023-07-20 23:09:32 +00:00
Robert Griesemer
cd6c4e0557 spec: clarify prose in rule for clear built-in
Per feedback on #56351.

For #56351.

Change-Id: I63dd1713a1efe4d7180d932dbd8e1510cbb32e90
Reviewed-on: https://go-review.googlesource.com/c/go/+/510935
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2023-07-18 23:43:01 +00:00
Robert Griesemer
01b649b7ef spec: explain in which situations function type arguments can be omitted
Change-Id: I9f008dba7ba6e30f0e62647482a3ed0b51bc1ad0
Reviewed-on: https://go-review.googlesource.com/c/go/+/502997
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2023-06-14 17:00:00 +00:00
Robert Griesemer
17dcbd8662 spec: de-emphasize string(int) conversions
Fixes #60731.

Change-Id: I71fad1c8385b13d036bb0ce7ae6bd21e0f596e51
Reviewed-on: https://go-review.googlesource.com/c/go/+/502657
Reviewed-by: Ian Lance Taylor <iant@google.com>
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2023-06-13 17:41:11 +00:00
Robert Griesemer
ee5af6103d spec: document new program initialization process
For #57411.

Change-Id: I94982d939d16ad17174f801cc167cc10ddc8da30
Reviewed-on: https://go-review.googlesource.com/c/go/+/501696
Reviewed-by: Keith Randall <khr@google.com>
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2023-06-13 17:40:15 +00:00
Robert Griesemer
72b08dbaf3 spec: add temporary note to type inference section
The section on type inference has not been updated yet for Go 1.21.
Add a temporary note so that readers referred to this section from
the release notes are not confused.

Change-Id: Idc4c74d6d700f891c625289e873ad5aa9c2c5213
Reviewed-on: https://go-review.googlesource.com/c/go/+/501308
Reviewed-by: Ian Lance Taylor <iant@google.com>
Reviewed-by: Robert Griesemer <gri@google.com>
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2023-06-07 22:14:14 +00:00
Robert Griesemer
1aaf1b219a spec: clarify min/max rules for numeric arguments (exclude NaNs)
Fixes #60570.

Change-Id: I7ef834731ea26ceee5ec9b7438fdd8323aaf828e
Reviewed-on: https://go-review.googlesource.com/c/go/+/500416
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2023-06-06 21:23:09 +00:00
Robert Griesemer
f9d114d0e8 spec: document min and max built-ins
For #59488.

Change-Id: I50f65216bf02b42c1e0619702833f4a6dbed8925
Reviewed-on: https://go-review.googlesource.com/c/go/+/498136
Reviewed-by: Rob Pike <r@golang.org>
Reviewed-by: Robert Griesemer <gri@google.com>
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2023-05-25 21:09:38 +00:00
Robert Griesemer
15a4e0d970 spec: re-order built-ins sections alphabetically (more or less)
Put the sections for the various built-ins into alphabetical order
based on the built-in name, while keeping built-ins that belong
together together.

The order is now (captialized letter determines order):

- Append
- Clear
- Close
- Complex, real, imag
- Delete
- Len, cap
- Make
- Min, max (to be inserted here)
- New
- Panic, recover
- Print, println

There are some white space adjustments but no changes to the prose
of the moved sections.

Change-Id: Iaec509918c6bc965df3f28656374de03279bdc9e
Reviewed-on: https://go-review.googlesource.com/c/go/+/498135
Reviewed-by: Robert Griesemer <gri@google.com>
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2023-05-24 22:24:59 +00:00
Daniel Frederick Crisman
e7b04a3e16 doc: correct spelling on placeholder
"placeholder" (no space) is already used in the spec and seems to be
the preferred option.

Removed space from "place holder".

Change-Id: I9b98f62f0e3f5adb019b99f5271cc9d19abf505e
GitHub-Last-Rev: ed5aaf9d02
GitHub-Pull-Request: golang/go#59626
Reviewed-on: https://go-review.googlesource.com/c/go/+/484576
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2023-04-13 23:15:09 +00:00
Daniel Frederick Crisman
6e8eec7328 doc: add missing oxford comma in Constants
In the language specification under "Constants" the lists matching default
types to untyped contstant types is missing an Oxford comma in the first
list. I found a number of other places in the spec and #23442 that use the
Oxford comma to support its use.

Add missing Oxford comma in Constants default type list.

Change-Id: I4562d692610334bc82452db076145d2414617a04
GitHub-Last-Rev: 8acdb60d6e
GitHub-Pull-Request: golang/go#59528
Reviewed-on: https://go-review.googlesource.com/c/go/+/483555
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2023-04-11 17:02:02 +00:00
cui fliter
df6d442c38 doc: fix "are" to "or" in core types
Fixes #59506

Change-Id: I2f8b92e93b706b061ca0eb0bd52e5cf798ce9ede
Reviewed-on: https://go-review.googlesource.com/c/go/+/483358
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2023-04-11 01:45:40 +00:00
Cuong Manh Le
99bc53f5e8 doc: add clear builtin to spec
Fixes #56351

Change-Id: Ia87bf594553b7d0464b591106840f849571c5f39
Reviewed-on: https://go-review.googlesource.com/c/go/+/467755
Auto-Submit: Cuong Manh Le <cuong.manhle.vn@gmail.com>
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2023-02-20 02:28:50 +00:00
Cuong Manh Le
2baf8ad831 doc: do not use "==" in slice examples
There's no slice comparison in Go.

Change-Id: I5de1766c2adeb56ed12a577a4c46c12b2582b1c8
Reviewed-on: https://go-review.googlesource.com/c/go/+/469015
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2023-02-19 23:51:51 +00:00
Cuong Manh Le
135c470b22 doc: add missing builtin functions not permitted in statement context
The typechecker already enforces this semantic, but the spec is not
updated when unsafe.{SliceData,String,StringData} were added.

Change-Id: I4ee8c564d5681b2a5fd31ff424a31bdf065d9f3b
Reviewed-on: https://go-review.googlesource.com/c/go/+/467756
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2023-02-16 19:49:55 +00:00
Oleksandr Redko
f63ee8b2c7 doc: fix spec typo
Change-Id: I5e3aca2b8fc78f38c9e2cdc67adf86d57ac85b1c
GitHub-Last-Rev: 0e5ddffe33
GitHub-Pull-Request: golang/go#58353
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2023-02-07 23:37:57 +00:00
Russ Cox
aa51c40b1c runtime: replace panic(nil) with panic(new(runtime.PanicNilError))
Long ago we decided that panic(nil) was too unlikely to bother
making a special case for purposes of recover. Unfortunately,
it has turned out not to be a special case. There are many examples
of code in the Go ecosystem where an author has written panic(nil)
because they want to panic and don't care about the panic value.

Using panic(nil) in this case has the unfortunate behavior of
making recover behave as though the goroutine isn't panicking.
As a result, code like:

	func f() {
		defer func() {
			if err := recover(); err != nil {
				log.Fatalf("panicked! %v", err)
			}
		}()
		call1()
		call2()
	}

looks like it guarantees that call2 has been run any time f returns,
but that turns out not to be strictly true. If call1 does panic(nil),
then f returns "successfully", having recovered the panic, but
without calling call2.

Instead you have to write something like:

	func f() {
		done := false
		defer func() {
			if err := recover(); !done {
				log.Fatalf("panicked! %v", err)
			}
		}()
		call1()
		call2()
		done = true
	}

which defeats nearly the whole point of recover. No one does this,
with the result that almost all uses of recover are subtly broken.

One specific broken use along these lines is in net/http, which
recovers from panics in handlers and sends back an HTTP error.
Users discovered in the early days of Go that panic(nil) was a
convenient way to jump out of a handler up to the serving loop
without sending back an HTTP error. This was a bug, not a feature.
Go 1.8 added panic(http.ErrAbortHandler) as a better way to access the feature.
Any lingering code that uses panic(nil) to abort an HTTP handler
without a failure message should be changed to use http.ErrAbortHandler.

Programs that need the old, unintended behavior from net/http
or other packages can set GODEBUG=panicnil=1 to stop the run-time error.

Uses of recover that want to detect panic(nil) in new programs
can check for recover returning a value of type *runtime.PanicNilError.

Because the new GODEBUG is used inside the runtime, we can't
import internal/godebug, so there is some new machinery to
cross-connect those in this CL, to allow a mutable GODEBUG setting.
That won't be necessary if we add any other mutable GODEBUG settings
in the future. The CL also corrects the handling of defaulted GODEBUG
values in the runtime, for #56986.

Fixes #25448.

Change-Id: I2b39c7e83e4f7aa308777dabf2edae54773e03f5
Reviewed-on: https://go-review.googlesource.com/c/go/+/461956
Reviewed-by: Robert Griesemer <gri@google.com>
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2023-01-19 22:21:50 +00:00
Robert Griesemer
357ea85892 spec: fix typo
Fixes #57323.

Change-Id: I77d3d747aa4746bb9a8cca0c0500ff8fa6ae33a3
Reviewed-on: https://go-review.googlesource.com/c/go/+/457915
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2022-12-15 16:18:42 +00:00
Robert Griesemer
ea14d1b6e1 spec: document which recursive arrays and structs are valid/invalid
Fixes #5069.

Change-Id: I4bc0f52a9cd1e64a49846dffeb4be5cbecc29a96
Reviewed-on: https://go-review.googlesource.com/c/go/+/457342
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2022-12-14 22:29:38 +00:00
Robert Griesemer
5c682f94c6 spec: document illegal recursive type parameter lists
Fixes #40882.

Change-Id: I90f99d75e6d66f857b6ab8789c6d436f85d20993
Reviewed-on: https://go-review.googlesource.com/c/go/+/457515
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2022-12-14 19:13:24 +00:00
Robert Griesemer
bd42aa86d3 spec: describe new semantics for comparable and constraint satisfaction
For #56548.
Fixes #57012.

Change-Id: I44f850522e52b1811025fb31bcef289da8f8089d
Reviewed-on: https://go-review.googlesource.com/c/go/+/457437
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2022-12-14 19:13:10 +00:00
Robert Griesemer
ffefcd360b spec: introduce notion of strict comparability
- Rephrase the notion of "comparability" from a property
  of values (operands) to a property of types and adjust
  dependent prose.
- Introduce the notion of "strict comparability".
- Fix the definitions of comparability for type interfaces
  and type parameters.
- Define the predeclared identifier "comparable" as stricly
  comparable.

These changes address existing problems in the spec as outlined
in the section on "Related spec issues" in issue #56548.

For #56548.

Change-Id: Ibc8c2f36d92857a5134eadc18358624803d3dd21
Reviewed-on: https://go-review.googlesource.com/c/go/+/457095
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2022-12-14 19:12:15 +00:00
Zhizhen He
8247b9f17a doc: fix typo
Change-Id: Ie639fe39b83336c0d885cdcb2fddc06f2b06c2dd
GitHub-Last-Rev: b5cc78ad42
GitHub-Pull-Request: golang/go#57082
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2022-12-08 19:06:14 +00:00
Tim King
60525dc31d spec: document conversion from slice to array
Document that a slice can be converted to either an array or a pointer
to an array of a matching underlying array type. This was documented in
the "Conversions from slice to array or array pointer" subsection, but
not in the list of conversion rules.

Updates #46505.

Change-Id: I16a89a63ef23c33580129952415e977a8f334009
Reviewed-on: https://go-review.googlesource.com/c/go/+/452936
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2022-11-30 17:03:21 +00:00
Robert Griesemer
72fdecafc0 spec: add a link to Allocation section in section on append built-in
If needed, the built-in function append allocates a new underlying
array. While we (probably) don't want to specify exactly how much
is allocated (the prose is deliberately vague), if there's more
space allocated than needed (cap > len after allocation), that
extra space is zeroed. Use an explicit link to the section on
Allocation which explicitly states that newly allocated memory
is zeroed.

Fixes #56684.

Change-Id: I9805d37c263b87860ea703ad143f738a0846247e
Reviewed-on: https://go-review.googlesource.com/c/go/+/452619
Reviewed-by: Ian Lance Taylor <iant@google.com>
Run-TryBot: Robert Griesemer <gri@google.com>
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Reviewed-by: Joseph Tsai <joetsai@digital-static.net>
Reviewed-by: Matthew Dempsky <mdempsky@google.com>
2022-11-23 00:25:09 +00:00
Robert Griesemer
753ad5e1d5 spec: document that trailing comma is valid after index in index expressions
At parse time we don't know if a[i] is an index expression or a
type (or function) instantiation. Because instantiations accept
a list of type arguments, and argument lists permit a trailing
comma, a[i,] is either an instantiation or index expression.

Document that a trailing comma is permitted in the syntax for
index expressions.

For comparison, the same problem arises with conversions which
cannot be distinguished from function calls at parse time. The
spec also permits a trailing comma for conversions T(x,). The
grammar adjustment is the same (see line 5239).

Fixes #55007.

Change-Id: Ib9101efe52031589eb95a428cc6dff940d939f9e
Reviewed-on: https://go-review.googlesource.com/c/go/+/452618
Reviewed-by: Ian Lance Taylor <iant@google.com>
Reviewed-by: Matthew Dempsky <mdempsky@google.com>
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2022-11-23 00:25:08 +00:00
Robert Griesemer
c55d184151 spec: document the new unsafe functions SliceData, String, and StringData
For #53003.

Change-Id: If5d76c7b8dfcbcab919cad9c333c0225fc155859
Reviewed-on: https://go-review.googlesource.com/c/go/+/449537
Reviewed-by: Matthew Dempsky <mdempsky@google.com>
Reviewed-by: Ian Lance Taylor <iant@google.com>
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2022-11-14 05:30:16 +00:00
Robert Griesemer
2041bde2b6 spec: clarify struct field and array element comparison order
Fixes #8606.

Change-Id: I64b13b2ed61ecae4641264deb47c9f7653a80356
Reviewed-on: https://go-review.googlesource.com/c/go/+/449536
Reviewed-by: Matthew Dempsky <mdempsky@google.com>
Reviewed-by: Ian Lance Taylor <iant@google.com>
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2022-11-14 01:28:11 +00:00
Cuong Manh Le
334984a92a spec: describe an edge case for slice expression of nil slice
Change-Id: I8c0e2b37e7e8cb4db6ad0b456fde7eb908ffbd04
Reviewed-on: https://go-review.googlesource.com/c/go/+/430836
Reviewed-by: Robert Griesemer <gri@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org>
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Reviewed-by: Cherry Mui <cherryyz@google.com>
Auto-Submit: Robert Griesemer <gri@google.com>
2022-09-21 14:06:17 +00:00
Cuong Manh Le
4b58b30778 spec: describe an edge case of slice-to-array conversions
Converting from nil slice to zero element array is ok, so explicitly
describe the behavior in the spec.

For #46505

Change-Id: I68f432deb6c21a7549bf7e870185fc62504b37f7
Reviewed-on: https://go-review.googlesource.com/c/go/+/430835
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2022-09-21 14:06:15 +00:00
VRDighe
0bfa9f0435 spec: fix typo in a type parameter example
Fixes #54973

Change-Id: Ibad9dd124617a1bbc23abd17cbd6e9e9928e3ed9
GitHub-Last-Rev: 1c6affb967
GitHub-Pull-Request: golang/go#55021
Reviewed-on: https://go-review.googlesource.com/c/go/+/430316
Reviewed-by: Cherry Mui <cherryyz@google.com>
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2022-09-20 15:50:36 +00:00
Robert Griesemer
2c3187cd42 spec: describe slice-to-array conversions
For #46505.

Change-Id: I1a30fd895496befd16626afb48717ac837ed5778
Reviewed-on: https://go-review.googlesource.com/c/go/+/429315
Reviewed-by: Matthew Dempsky <mdempsky@google.com>
Reviewed-by: Ian Lance Taylor <iant@golang.org>
Reviewed-by: Robert Griesemer <gri@google.com>
2022-09-08 16:37:47 +00:00
Robert Griesemer
17083a2fdf spec: retitle section on "Assignments" to "Assignment statements"
This permits a clear distinction between an individual assignment
and an assignment statement which may assign more than one value.
It also makes this section title consistent with all other section
titles about statements. Adjust internal links and prose where
appropriate. (Note that the spec already referred to assignment
statements in a couple of places, even before this change.)

Add an introductory paragraph to the section on assignment statements.

Preparation for adding a section on value vs reference types
(issue #5083).

Change-Id: Ie140ac296e653c67da2a5a203b63352b3dc4f9f5
Reviewed-on: https://go-review.googlesource.com/c/go/+/413615
Reviewed-by: Robert Griesemer <gri@google.com>
Reviewed-by: Ian Lance Taylor <iant@google.com>
2022-06-30 00:58:41 +00:00
Robert Griesemer
f2c7e78592 spec: document operations which accept []byte|string constrained types
Pre-1.18, as special cases, the built-in operations append and copy
accepted strings as second arguments if the first argument was a byte
slice. With Go 1.18, these two built-ins as well as slice expressions
rely on the notion of core types in their specification.

Because we want to permit slice expressions, append, and copy to
operate on (1st or 2nd operands) that are type parameters restricted
by []byte | string (and variations thereof), the simple notion of
core type is not sufficient for these three operations. (The compiler
already permits such more relaxed operations).

In the section on core types, add a paragraph and examples introducing
the (artificial) core type "bypestring", which describes the core type
of type sets whose underlying types are []byte or string. Adjust the
rules for slice expressions, append, and copy accordingly.

Also (unrelated): Adjust prose in the only paragraph where we used
personal speech ("we") to impersonal speech, to match the rest of
the spec.

Fixes #52859.

Change-Id: I1cbda3095a1136fb99334cc3a62a9a349a27ce1e
Reviewed-on: https://go-review.googlesource.com/c/go/+/412234
Reviewed-by: Ian Lance Taylor <iant@google.com>
Reviewed-by: Robert Griesemer <gri@google.com>
2022-06-21 23:17:35 +00:00
Robert Griesemer
bcce8ef498 spec: adjust incorrect sentence in section on rune literals
Add an additional example.

Fixes #53217.

Change-Id: I899376b9c1fa8dc5d475d8d3d6c8788ab79b0847
Reviewed-on: https://go-review.googlesource.com/c/go/+/412238
Reviewed-by: Robert Griesemer <gri@google.com>
Reviewed-by: Ian Lance Taylor <iant@golang.org>
Auto-Submit: Robert Griesemer <gri@google.com>
Reviewed-by: Ian Lance Taylor <iant@google.com>
2022-06-16 16:22:37 +00:00
Robert Griesemer
0dffda1383 spec: clarify "slice of bytes" and "slice of runes" through examples
The spec section on conversions uses the terms "slice of bytes" and
"slice of runes". While not obviously clear, what is meant are slice
types whose element types are byte or rune types; specifically the
underlying types of the slices' element types must be byte or rune.

Some of this was evident from the examples, but not all of it. Made
this clearer by adding more examples illustrating various permitted
conversions.

Note that the 1.17 compiler did not accept the following conversions:

        string([]myByte{...})
        string([]myRune{...})
        myString([]myByte{...})
        myString([]myRune{...})

(where myByte, myRune, and myString have underlying types of byte,
rune, and string respectively) - it reported an internal error.
But it did accept the inverse conversions:

        []myByte("...")
        []myRune("...")
        []myByte(myString("..."))
        []myRune(myString("..."))

The 1.18 compiler made those conversions symmetric and they are now
permitted in both directions.

The extra examples reflect this reality.

Fixes #23814.

Change-Id: I5a1c200b45ddd0e8c0dc0d11da3a6c39cb2dc848
Reviewed-on: https://go-review.googlesource.com/c/go/+/412094
Reviewed-by: Robert Griesemer <gri@google.com>
Reviewed-by: Ian Lance Taylor <iant@google.com>
2022-06-14 23:44:35 +00:00
Robert Griesemer
5ee939b819 spec: clarify behavior of map size hint for make built-in
The spec already states that the precise behavior of the map size
hint provided to the make built-in is implementation-dependent.

Exclude requiring specific run-time behavior for maps.
(The current Go compiler does not panic if the size hint is negative
at run-time.)

Fixes #53219.

Change-Id: I2f3618bf9ba4ed921e18dc4f2273eaa770805bd7
Reviewed-on: https://go-review.googlesource.com/c/go/+/411919
Reviewed-by: Keith Randall <khr@google.com>
Reviewed-by: Ian Lance Taylor <iant@google.com>
Reviewed-by: Keith Randall <khr@golang.org>
2022-06-13 19:06:53 +00:00
Robert Griesemer
4703546a29 spec: add missing optional type arguments after TypeName in syntax
Types may be generic, so each occurrence of a TypeName may be
followed by optional type arguments. Add the missing syntactic
(EBNF) factor.

The syntax of type names followed by type arguments matches the
syntax of operand names followed by type arguments (operands may
also be types, or generic functions, among other things). This
opens the door to factoring out this shared syntax, but it will
also require some adjustments to prose to make it work well.
Leaving for another change.

Fixes #53240.

Change-Id: I15212225c28b27f7621e3ca80dfbd131f6b7eada
Reviewed-on: https://go-review.googlesource.com/c/go/+/411918
Reviewed-by: Ian Lance Taylor <iant@google.com>
Reviewed-by: Robert Griesemer <gri@google.com>
2022-06-13 19:06:49 +00:00
George Looshch
fd0ffedae2 doc: replace tabs with spaces for alignment in code snippets
Fixes #52255

Change-Id: Ibb518cf2f6bac9e1ffc426a014afe80cc4c0df5e
Reviewed-on: https://go-review.googlesource.com/c/go/+/399394
Reviewed-by: Jamal Carvalho <jamal@golang.org>
Reviewed-by: Robert Griesemer <gri@google.com>
2022-05-26 23:22:37 +00:00