There is a subtle distinction between a value
*being* the zero value vs being *equal to* the zero value.
This was discussed at length in #31450.

Using "a zero value" in the docs suggests that there may
be more than zero value. That is possible on the "equal to
zero value" reading, but not the "is zero" reading that we
selected for the semantics of IsZero.

This change attempts to prevent any confusion on this front by
switching to "the zero value" in the documentation.

And while we're here, eliminate a double-space.
(Darn macbook keyboards.)

Change-Id: Iaa02ba297438793f5a90be9919a4d53baef92f8e
Reviewed-on: https://go-review.googlesource.com/c/go/+/182617
Run-TryBot: Josh Bleecher Snyder <josharian@gmail.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>

Change-Id: I692229a5597a6114a7f4261f7b59c58bf20f3e2b
GitHub-Last-Rev: ab173354caa63345d38a625705aea0c660cfdb9b
GitHub-Pull-Request: golang/go#32660
Reviewed-on: https://go-review.googlesource.com/c/go/+/182677Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>

This fixes a regression introduced in CL 180337. When we query a
module at "latest" that has no tagged versions, we tried to use ""
as the version because we used info.Name instead of info.Version. This
only happened when using a proxy: in direct mode, info.Name is set to
the underlying VCS revision, which is fine.

Also: serve "/mod/path/@latest" through our test proxy.
Previously, we served a 404, which made this bug hard to detect.

Fixes #32636

Change-Id: I5c60975656297f862cad66675170e819685ebd39
Reviewed-on: https://go-review.googlesource.com/c/go/+/182697
Run-TryBot: Jay Conrod <jayconrod@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Bryan C. Mills <bcmills@google.com>

This change updates the doc comments of the various ParseGlob functions
and methods to state that they use the semantics of filepath.Match when
matching the file name pattern.

Fixes #30608

Change-Id: Iee4bdc0a2a2f8647d1f9a910e4d72a5de9204d11
Reviewed-on: https://go-review.googlesource.com/c/go/+/179739Reviewed-by: Dmitri Shuralyov <dmitshur@golang.org>

Write release notes for a few reflect, runtime, and syscall changes.

The init randomization has been reverted.

Change-Id: Idae481ca015e325eb7302abaa15b2792312f4c32
Reviewed-on: https://go-review.googlesource.com/c/go/+/181577Reviewed-by: Austin Clements <austin@google.com>

Add a special case to print a generic nil error when context.err is
nil.

Previously, this case was unchecked, leading to a call to (*Error).Error
with a nil receiver, which was triggering a nil pointer access. However,
this bug was masked by the panic-recovery code in package fmt.

I tested this change by running `dlv test` in src/html/template, running
the `continue` command, and verifying that no "bad access" errors are
returned.

Fixes #28854

Change-Id: I0b637b943de003d9efc294f6f1e49b793668d037
Reviewed-on: https://go-review.googlesource.com/c/go/+/181579Reviewed-by: Dmitri Shuralyov <dmitshur@golang.org>

* In doc/install-source.html, clarify the meaning of $GOBIN and
  describe where executables from the Go distribution are
  installed. Also describe $GOPATH, since it provides a default value
  for $GOBIN and may conflict with $GOROOT.
* Add more detail to 'go help install' as well.

Fixes #31576

Change-Id: Ib8a8c21677c3aa0ebef97a3b587b6f8fe338b80e
Reviewed-on: https://go-review.googlesource.com/c/go/+/182341
Run-TryBot: Jay Conrod <jayconrod@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Bryan C. Mills <bcmills@google.com>

Fixes the test on the linux-arm64-packet builder.

Change-Id: Icaf9edf9542f4f6e3791ca43298a1e7051eaa576
Reviewed-on: https://go-review.googlesource.com/c/go/+/182378
Run-TryBot: Elias Naur <mail@eliasnaur.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>

It is forbidden by App Store.

Fixes #31628

Change-Id: Ie6d14a524ee55b57af8db685f3a79f474733add5
Reviewed-on: https://go-review.googlesource.com/c/go/+/182297
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Keith Randall <khr@golang.org>

Change-Id: Icfd5b9d1ca757081af7885189ae7094fa1b3d8f1
Reviewed-on: https://go-review.googlesource.com/c/go/+/182377
Run-TryBot: Elias Naur <mail@eliasnaur.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Ian Lance Taylor <iant@golang.org>

Changes Darwin semaphore support from using pthread mutexes and
condition variables to using dispatch semaphores. Signaling a dispatch
semaphore is async-signal-safe.

Fixes #31264

Change-Id: If0ce47623501db13e3804b14ace5f4d8eaef461e
Reviewed-on: https://go-review.googlesource.com/c/go/+/182258Reviewed-by: Elias Naur <mail@eliasnaur.com>
Reviewed-by: Keith Randall <khr@golang.org>

Change-Id: I0ee4b4f0211cd12803ab33976669350d9dd615f3
Reviewed-on: https://go-review.googlesource.com/c/go/+/181944Reviewed-by: Andrew Bonventre <andybons@golang.org>

Change-Id: Ifd330053094c172b7dcd9086da173289efc7f9b8
Reviewed-on: https://go-review.googlesource.com/c/go/+/181942Reviewed-by: Katie Hockman <katie@golang.org>
Reviewed-by: Andrew Bonventre <andybons@golang.org>

Currently, 'go get -u' and 'go get -u=patch' avoid accidentally
downgrading modules by preventing upgrades in two cases:

1) If the current version is a prerelease that is semantically later
   than the "latest" or "patch" version.
2) If the current version is a pseudoversion that is chronologically
   newer than the "latest" or "patch" version.

With this change, 'go get m@latest' and 'go get m@patch' prevent
downgrades using the same checks.

Also: 'go get m@patch' now works if m is a module path but not a
package path (i.e., there is no package in the module root directory).

Fixes #30634
Fixes #32537

Change-Id: I916630c385b5f3ba7c13e0d65ba08f73a1a67829
Reviewed-on: https://go-review.googlesource.com/c/go/+/180337
Run-TryBot: Jay Conrod <jayconrod@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Bryan C. Mills <bcmills@google.com>

Change-Id: I4c52d9bcf941810dbdfdd39e7f339c8283d6bcc7
Reviewed-on: https://go-review.googlesource.com/c/go/+/181937Reviewed-by: Katie Hockman <katie@golang.org>

Pick up asm ppc64le implementations for internal/chacha20 and
poly1305.

Change-Id: Ide6fc91da3b10d1c3d9e8e00957c52be06a3cf93
Reviewed-on: https://go-review.googlesource.com/c/go/+/181877
Run-TryBot: Lynn Boger <laboger@linux.vnet.ibm.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Carlos Eduardo Seo <cseo@linux.vnet.ibm.com>

Change-Id: I2a0bd295ad9737581d149a7165191b878ae2acda
Reviewed-on: https://go-review.googlesource.com/c/go/+/181880Reviewed-by: Ian Lance Taylor <iant@golang.org>

Add support for scanning decimal types into values. If the dest
supports the decimal composer interface and the src supports
the decimal decomposer, set the value of the decimal when Scanning.

Add support for sending decimal decomposer interface values
as parameters.

For #30870

Change-Id: Ic5dbf9069df8d56405852b17542a9188d55c2947
Reviewed-on: https://go-review.googlesource.com/c/go/+/174181
Run-TryBot: Daniel Theophanes <kardianos@gmail.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Ian Lance Taylor <iant@golang.org>

Exposing the underlying driver conn will allow the use of the
standard connection pool while still able to run special function
directly on the driver.

Fixes #29835

Change-Id: Ib6d3b9535e730f008916805ae3bf76e4494c88f9
Reviewed-on: https://go-review.googlesource.com/c/go/+/174182
Run-TryBot: Daniel Theophanes <kardianos@gmail.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Ian Lance Taylor <iant@golang.org>

Factor the try-on-failure variants are now in the package
cmd/go/internal/robustio.

Add to them a RemoveAll variant using the same retry loop,
and use it to attempt to address the observed flakes in
TestLinkXImportPathEscape.

Fixes #19491
Updates #25965
Updates #28387
Updates #32188

Change-Id: I9db1a0c7537b8aaadccab1b9eca734595668ba29
Reviewed-on: https://go-review.googlesource.com/c/go/+/181541
Run-TryBot: Bryan C. Mills <bcmills@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Alex Brainman <alex.brainman@gmail.com>
Reviewed-by: Jay Conrod <jayconrod@google.com>
Reviewed-by: Russ Cox <rsc@golang.org>

Also, in 'go get' in GOPATH mode, report an error for package paths
that start with '-'.

Change-Id: Ic2575381aa2d093ba15c53b893bf2eaded8b6066
Reviewed-on: https://go-review.googlesource.com/c/go/+/181237
Run-TryBot: Jay Conrod <jayconrod@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Dmitri Shuralyov <dmitshur@golang.org>
Reviewed-by: Bryan C. Mills <bcmills@google.com>

Change-Id: I71a6816f54f8ad0f8531bb3f9de552fd136a0ed4
Reviewed-on: https://go-review.googlesource.com/c/go/+/181943Reviewed-by: Ian Lance Taylor <iant@golang.org>

Change-Id: Ifdc3c5b840e6833f14c8e52948e45d5faa5a0615
Reviewed-on: https://go-review.googlesource.com/c/go/+/181940Reviewed-by: Ian Lance Taylor <iant@golang.org>

While it is possible for the connection pool to guard against panics
on every valuer read, this seems like a high cost to be added,
in both code complexity and possible runtime performance.

Most uses of the Valuer will be trivial, like returning
a struct field. Optimize for that case. If sometime may panic the
valuer should itself use recover and return an error.

Fixes #26332

Change-Id: Iad18780b8028f669f5a7841b74a5384d62fb6a7e
Reviewed-on: https://go-review.googlesource.com/c/go/+/170700Reviewed-by: Ian Lance Taylor <iant@golang.org>

This change makes the release notes for Go 1.13 more complete
by mentioning a new function in the os package.

Change-Id: I0d637fd70ff6d14782bbfb7c13985a0f83b19d6d
Reviewed-on: https://go-review.googlesource.com/c/go/+/181945Reviewed-by: Ian Lance Taylor <iant@golang.org>

Change-Id: Ib5417cc48959b03befb1579da3281415a11ede9f
Reviewed-on: https://go-review.googlesource.com/c/go/+/181879Reviewed-by: Dmitri Shuralyov <dmitshur@golang.org>

It is too confusing to have to set GONOSUMDB and GONOPROXY
in common use cases, but one cannot be guaranteed to be a
subset of the other.

This CL adds GOPRIVATE, which takes the same kind of pattern list
but is defined as "these patterns are private (non-public) modules".
Today the implication is that GOPRIVATE is the default setting for
GONOSUMDB and GONOPROXY. If there are other accommodations
to make for private packages in the future or in other tools,
having this clear statement of intent will let us do that.
(For example maybe an IDE integration would hyperlink an import
path to godoc.org; consulting GOPRIVATE would be a reasonable
way to decide not to do that for certain imports. In contrast,
consulting GONOPROXY or GONOSUMDB clearly would not.)

Fixes #32184.

Change-Id: If54c12d353c7a0a5c0e0273764140cce3c154a02
Reviewed-on: https://go-review.googlesource.com/c/go/+/181719
Run-TryBot: Russ Cox <rsc@golang.org>
Reviewed-by: Bryan C. Mills <bcmills@google.com>
Reviewed-by: Jay Conrod <jayconrod@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>

For int8, int16, and int32, comparing their unsigned value to MaxInt64
to determine non-negativity doesn't make sense, because they have
negative values whose unsigned representation is smaller than that.
Fix is simply to compare with the appropriate upper bound based on the
value type's size.

Fixes #32560.

Change-Id: Ie7afad7a56af92bd890ba5ff33c86d1df06cfd9a
Reviewed-on: https://go-review.googlesource.com/c/go/+/181797
Run-TryBot: Matthew Dempsky <mdempsky@google.com>
Reviewed-by: Josh Bleecher Snyder <josharian@gmail.com>
Reviewed-by: David Chase <drchase@google.com>
Reviewed-by: Keith Randall <khr@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>

Change-Id: I032a3342c3ac899a39d357420b981b6f281518f6
Reviewed-on: https://go-review.googlesource.com/c/go/+/181939Reviewed-by: Daniel Theophanes <kardianos@gmail.com>

Change-Id: I49b09349a632a6b6219c85638d9cb6774c0c210a
Reviewed-on: https://go-review.googlesource.com/c/go/+/181721Reviewed-by: Bryan C. Mills <bcmills@google.com>

Change-Id: Idb5bf2a61bff635e3ebd926bdeacf943578ac874
Reviewed-on: https://go-review.googlesource.com/c/go/+/181681Reviewed-by: Ian Lance Taylor <iant@golang.org>
Reviewed-by: Bryan C. Mills <bcmills@google.com>

Make "go test" run the new errorsas vet check by default.

Fixes #31213.

Change-Id: I5c93c000874ffe1c0b6d647bf10de803f414c5c1
Reviewed-on: https://go-review.googlesource.com/c/go/+/179977
Run-TryBot: Jonathan Amsterdam <jba@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Michael Matloob <matloob@golang.org>

Change-Id: I389d140e8fd2849e4dc438246add47819f6b25a3
Reviewed-on: https://go-review.googlesource.com/c/go/+/181300Reviewed-by: Bryan C. Mills <bcmills@google.com>

Fixes #32191

Change-Id: I6eebe1d4975e904c906e6b839cd6cab9447cbb34
Reviewed-on: https://go-review.googlesource.com/c/go/+/181019
Run-TryBot: Bryan C. Mills <bcmills@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Russ Cox <rsc@golang.org>

Change-Id: I4923f0726ae0261a7c7b0f85e7433ae0f605c123
Reviewed-on: https://go-review.googlesource.com/c/go/+/181738Reviewed-by: Bryan C. Mills <bcmills@google.com>

This change revendors golang.org/x/tools to include the check and
modifies cmd/vet to add it to the command.

CL 179977 will enable the check by default for 'go test'.

Commands run (starting in GOROOT/src):
	cd cmd
	emacs vet/main.go
	go get -u=patch golang.org/x/tools/go/analysis/passes/errorsas@latest
	go mod tidy
	go mod vendor
	cd ..
	./make.bash
	go test all

Updates #31213

Change-Id: Ic2ba9bd2d31c4c5fd9e7c42ca14e8dc38520c93b
Reviewed-on: https://go-review.googlesource.com/c/go/+/181717Reviewed-by: Jonathan Amsterdam <jba@google.com>

Check the value of target after As returns true.

Change-Id: I76a2b25fe825ee1dbb5f39f8f0b211c55bd25a4f
Reviewed-on: https://go-review.googlesource.com/c/go/+/181299Reviewed-by: Bryan C. Mills <bcmills@google.com>

Change-Id: I34fd45ee252474c12f2e9c8d9b1a75b9eabb57f2
Reviewed-on: https://go-review.googlesource.com/c/go/+/181549Reviewed-by: Bryan C. Mills <bcmills@google.com>

Change-Id: I8ae00d2392c20c627d58cf7e79015e982b971802
Reviewed-on: https://go-review.googlesource.com/c/go/+/181551Reviewed-by: Filippo Valsorda <filippo@golang.org>

Change-Id: I1c3e3305dfee4545a6caedd48243770ab3b28277
Reviewed-on: https://go-review.googlesource.com/c/go/+/181550Reviewed-by: Filippo Valsorda <filippo@golang.org>