SSLv3 has been irreparably broken since the POODLE attack 5 years ago
and RFC 7568 (f.k.a. draft-ietf-tls-sslv3-diediedie) prohibits its use
in no uncertain terms.

As announced in the Go 1.13 release notes, remove support for it
entirely in Go 1.14.

Updates #32716

Change-Id: Id653557961d8f75f484a01e6afd2e104a4ccceaf
Reviewed-on: https://go-review.googlesource.com/c/go/+/191976
Run-TryBot: Filippo Valsorda <filippo@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>

While working on #30645, I noticed that many instances
in which the walkinrange optimization could apply
were not even being considered.

This was because of extraneous blocks in the CFG,
of the type that shortcircuit normally removes.

The change improves the shortcircuit pass to handle
most of those cases. (There are a few that can only be
reasonably detected later in compilation, after other
optimizations have been run, but not enough to be worth chasing.)

Notable changes:

* Instead of calculating live-across-blocks values, use v.Uses == 1.
  This is cheaper and more straightforward.
  v.Uses did not exist when this pass was initially written.
* Incorporate a fusePlain and loop until stable.
  This is necessary to find many of the instances.
* Allow Copy and Not wrappers around Phi values.
  This significantly increases effectiveness.
* Allow removal of all preds, creating a dead block.
  The previous pass stopped unnecessarily at one pred.
* Use phielimValue during cleanup instead of manually
  setting the op to OpCopy.

The result is marginally faster compilation and smaller code.

name        old time/op       new time/op       delta
Template          213ms ± 2%        212ms ± 2%  -0.63%  (p=0.002 n=49+48)
Unicode          90.0ms ± 2%       89.8ms ± 2%    ~     (p=0.122 n=48+48)
GoTypes           710ms ± 3%        711ms ± 2%    ~     (p=0.433 n=45+49)
Compiler          3.23s ± 2%        3.22s ± 2%    ~     (p=0.124 n=47+49)
SSA               10.0s ± 1%        10.0s ± 1%  -0.43%  (p=0.000 n=48+50)
Flate             135ms ± 3%        135ms ± 2%    ~     (p=0.311 n=49+49)
GoParser          158ms ± 2%        158ms ± 2%    ~     (p=0.757 n=48+48)
Reflect           447ms ± 2%        447ms ± 2%    ~     (p=0.815 n=49+48)
Tar               189ms ± 2%        189ms ± 3%    ~     (p=0.530 n=47+49)
XML               251ms ± 3%        250ms ± 1%  -0.75%  (p=0.002 n=49+48)
[Geo mean]        427ms             426ms       -0.25%

name        old user-time/op  new user-time/op  delta
Template          265ms ± 2%        265ms ± 2%    ~     (p=0.969 n=48+50)
Unicode           119ms ± 6%        119ms ± 6%    ~     (p=0.738 n=50+50)
GoTypes           923ms ± 2%        925ms ± 2%    ~     (p=0.057 n=43+47)
Compiler          4.37s ± 2%        4.37s ± 2%    ~     (p=0.691 n=50+46)
SSA               13.4s ± 1%        13.4s ± 1%    ~     (p=0.282 n=42+49)
Flate             162ms ± 2%        162ms ± 2%    ~     (p=0.774 n=48+50)
GoParser          186ms ± 2%        186ms ± 3%    ~     (p=0.213 n=47+47)
Reflect           572ms ± 2%        573ms ± 3%    ~     (p=0.303 n=50+49)
Tar               240ms ± 3%        240ms ± 2%    ~     (p=0.939 n=46+44)
XML               302ms ± 2%        302ms ± 2%    ~     (p=0.399 n=47+47)
[Geo mean]        540ms             541ms       +0.07%

name        old alloc/op      new alloc/op      delta
Template         36.8MB ± 0%       36.7MB ± 0%  -0.42%  (p=0.008 n=5+5)
Unicode          28.1MB ± 0%       28.1MB ± 0%    ~     (p=0.151 n=5+5)
GoTypes           124MB ± 0%        124MB ± 0%  -0.26%  (p=0.008 n=5+5)
Compiler          571MB ± 0%        566MB ± 0%  -0.84%  (p=0.008 n=5+5)
SSA              1.86GB ± 0%       1.85GB ± 0%  -0.58%  (p=0.008 n=5+5)
Flate            22.8MB ± 0%       22.8MB ± 0%  -0.17%  (p=0.008 n=5+5)
GoParser         27.3MB ± 0%       27.3MB ± 0%  -0.20%  (p=0.008 n=5+5)
Reflect          79.5MB ± 0%       79.3MB ± 0%  -0.20%  (p=0.008 n=5+5)
Tar              34.7MB ± 0%       34.6MB ± 0%  -0.42%  (p=0.008 n=5+5)
XML              45.4MB ± 0%       45.3MB ± 0%  -0.29%  (p=0.008 n=5+5)
[Geo mean]       80.0MB            79.7MB       -0.34%

name        old allocs/op     new allocs/op     delta
Template           378k ± 0%         377k ± 0%  -0.22%  (p=0.008 n=5+5)
Unicode            339k ± 0%         339k ± 0%    ~     (p=0.643 n=5+5)
GoTypes           1.36M ± 0%        1.36M ± 0%  -0.10%  (p=0.008 n=5+5)
Compiler          5.51M ± 0%        5.50M ± 0%  -0.13%  (p=0.008 n=5+5)
SSA               17.5M ± 0%        17.5M ± 0%  -0.14%  (p=0.008 n=5+5)
Flate              234k ± 0%         234k ± 0%  -0.04%  (p=0.008 n=5+5)
GoParser           299k ± 0%         299k ± 0%  -0.05%  (p=0.008 n=5+5)
Reflect            978k ± 0%         979k ± 0%  +0.02%  (p=0.016 n=5+5)
Tar                351k ± 0%         351k ± 0%  -0.04%  (p=0.008 n=5+5)
XML                435k ± 0%         435k ± 0%  -0.11%  (p=0.008 n=5+5)
[Geo mean]         840k              840k       -0.08%

file      before    after     Δ       %
go        14794788  14770212  -24576  -0.166%
addr2line 4203688   4199592   -4096   -0.097%
api       5954056   5941768   -12288  -0.206%
asm       4862704   4846320   -16384  -0.337%
cgo       4778920   4770728   -8192   -0.171%
compile   24001568  23923792  -77776  -0.324%
cover     5198440   5190248   -8192   -0.158%
dist      3595248   3587056   -8192   -0.228%
doc       4618504   4610312   -8192   -0.177%
fix       3337416   3333320   -4096   -0.123%
link      6120408   6116312   -4096   -0.067%
nm        4149064   4140872   -8192   -0.197%
objdump   4555608   4547416   -8192   -0.180%
pprof     14616324  14595844  -20480  -0.140%
test2json 2766328   2762232   -4096   -0.148%
trace     11638844  11622460  -16384  -0.141%
vet       8274936   8258552   -16384  -0.198%
total     132520780 132270972 -249808 -0.189%

Change-Id: Ifcd235a2a6e5f13ed5c93e62523e2ef61321fccf
Reviewed-on: https://go-review.googlesource.com/c/go/+/178197
Run-TryBot: Josh Bleecher Snyder <josharian@gmail.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Keith Randall <khr@golang.org>

'git ls-remote' started recognizing the '--' separator at some point
after 2.7.4, but git defaults to version 2.7.4 on Ubuntu 16.04 LTS,
which remains supported by Ubuntu until April 2021.

We added '--' tokens to most VCS commands as a defensive measure in
CL 181237, but it isn't strictly necessary here because the 'scheme'
argument to our template is chosen from a predefined list: we can
safely drop it to retain compatibility.

Fixes #33836
Updates #26746

Change-Id: Ibb53366b95f8029b587e0b7646a439330d759ac7
Reviewed-on: https://go-review.googlesource.com/c/go/+/191978
Run-TryBot: Bryan C. Mills <bcmills@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Dmitri Shuralyov <dmitshur@golang.org>

CSE can make dead values live again.
Running deadcode first avoids that;
it also makes CSE more efficient.

file    before    after     Δ       %       
api     5970616   5966520   -4096   -0.069% 
asm     4867088   4846608   -20480  -0.421% 
compile 23988320  23935072  -53248  -0.222% 
link    6084376   6080280   -4096   -0.067% 
nm      4165736   4161640   -4096   -0.098% 
objdump 4572216   4568120   -4096   -0.090% 
pprof   14452996  14457092  +4096   +0.028% 
trace   11467292  11471388  +4096   +0.036% 
total   132181100 132099180 -81920  -0.062% 

Compiler performance impact is negligible:

name        old alloc/op      new alloc/op      delta
Template         38.8MB ± 0%       38.8MB ± 0%  -0.04%  (p=0.008 n=5+5)
Unicode          28.2MB ± 0%       28.2MB ± 0%    ~     (p=1.000 n=5+5)
GoTypes           131MB ± 0%        131MB ± 0%  -0.14%  (p=0.008 n=5+5)
Compiler          606MB ± 0%        606MB ± 0%  -0.05%  (p=0.008 n=5+5)
SSA              2.14GB ± 0%       2.13GB ± 0%  -0.26%  (p=0.008 n=5+5)
Flate            24.0MB ± 0%       24.0MB ± 0%  -0.18%  (p=0.008 n=5+5)
GoParser         28.8MB ± 0%       28.8MB ± 0%  -0.15%  (p=0.008 n=5+5)
Reflect          83.8MB ± 0%       83.7MB ± 0%  -0.11%  (p=0.008 n=5+5)
Tar              36.4MB ± 0%       36.4MB ± 0%  -0.09%  (p=0.008 n=5+5)
XML              47.9MB ± 0%       47.8MB ± 0%  -0.15%  (p=0.008 n=5+5)
[Geo mean]       84.6MB            84.5MB       -0.12%

name        old allocs/op     new allocs/op     delta
Template           379k ± 0%         380k ± 0%  +0.15%  (p=0.008 n=5+5)
Unicode            340k ± 0%         340k ± 0%    ~     (p=0.738 n=5+5)
GoTypes           1.36M ± 0%        1.36M ± 0%  +0.05%  (p=0.008 n=5+5)
Compiler          5.49M ± 0%        5.49M ± 0%  +0.12%  (p=0.008 n=5+5)
SSA               17.5M ± 0%        17.5M ± 0%  -0.18%  (p=0.008 n=5+5)
Flate              235k ± 0%         235k ± 0%    ~     (p=0.079 n=5+5)
GoParser           302k ± 0%         302k ± 0%    ~     (p=0.310 n=5+5)
Reflect            976k ± 0%         977k ± 0%  +0.08%  (p=0.008 n=5+5)
Tar                352k ± 0%         352k ± 0%  +0.12%  (p=0.008 n=5+5)
XML                436k ± 0%         436k ± 0%  -0.05%  (p=0.008 n=5+5)
[Geo mean]         842k              842k       +0.03%


Change-Id: I53e8faed1859885ca5c4a5d45067a50984f3eff1
Reviewed-on: https://go-review.googlesource.com/c/go/+/175879
Run-TryBot: Josh Bleecher Snyder <josharian@gmail.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Keith Randall <khr@golang.org>

The TestParseErrors test function was not strict with unwanted errors
received from url.Parse(). It was not failing in such cases, now it does

Fixes #33646
Updates #29098

Change-Id: I069521093e2bff8b1fcd41ffd3f9799f3108bc61
GitHub-Last-Rev: e6844c57f979ddb8418643d9c5244a5d1b4578ba
GitHub-Pull-Request: golang/go#33876
Reviewed-on: https://go-review.googlesource.com/c/go/+/191966
Run-TryBot: Filippo Valsorda <filippo@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Filippo Valsorda <filippo@golang.org>

Fixes golang/go#31249

Change-Id: I3280f8ab170ed31d4efb71106533e016d430d44c
Reviewed-on: https://go-review.googlesource.com/c/go/+/191557Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>

It was mistakenly re-enabled in CL 146217.

Fixes #33837

Change-Id: I8c0e1787114c6232df5888e51e355906622295bc
Reviewed-on: https://go-review.googlesource.com/c/go/+/191877
Run-TryBot: Filippo Valsorda <filippo@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Dmitri Shuralyov <dmitshur@golang.org>

Updates #33879

Change-Id: Ifc91490b1cb791fdf5ffe69ef81c0ec0e6cbecc3
Reviewed-on: https://go-review.googlesource.com/c/go/+/191997
Run-TryBot: Bryan C. Mills <bcmills@google.com>
Reviewed-by: Alexander Rakoczy <alex@golang.org>

Because the Node AST represents references to declared objects (e.g.,
variables, packages, types, constants) by directly pointing to the
referred object, we don't have use-position info for these objects.

For switch statements with duplicate cases, we report back where the
first duplicate value appeared. However, due to the AST
representation, if the value was a declared constant, we mistakenly
reported the constant declaration position as the previous case
position.

This CL reports back against the 'case' keyword's position instead, if
there's no more precise information available to us.

It also refactors code to emit the same "previous at" error message
for duplicate values in map literals.

Thanks to Emmanuel Odeke for the test case.

Fixes #33460.

Change-Id: Iec69542ccd4aad594dde8df02d1b880a422c5622
Reviewed-on: https://go-review.googlesource.com/c/go/+/188901Reviewed-by: Robert Griesemer <gri@golang.org>
Reviewed-by: Emmanuel Odeke <emm.odeke@gmail.com>
Run-TryBot: Emmanuel Odeke <emm.odeke@gmail.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>

Use efaceOf to safely convert from *interface{} to *_eface, and to
make it clearer what the pointer arithmetic is computing.

Incidentally, remove a spurious unsafe.Pointer->*uint8->unsafe.Pointer
round trip conversion in newproc.

No behavior change.

Change-Id: I2ad9d791d35d8bd008ef43b03dad1589713c5fd4
Reviewed-on: https://go-review.googlesource.com/c/go/+/190457
Run-TryBot: Matthew Dempsky <mdempsky@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Keith Randall <khr@golang.org>

I'm trying to keep the code changes minimal for backporting to Go 1.13,
so it is still possible for a handful of entries to leak,
but the leaks are now O(1) instead of O(N) in the steady state.

Longer-term, I think it would be a good idea to coalesce idleMu with
connsPerHostMu and clear entries out of both queues as soon as their
goroutines are done waiting.

Fixes #33849
Fixes #33850

Change-Id: Ia66bc64671eb1014369f2d3a01debfc023b44281
Reviewed-on: https://go-review.googlesource.com/c/go/+/191964
Run-TryBot: Bryan C. Mills <bcmills@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>

The assembly output for x & c == c, where c is power of 2:

	MOVQ	"".set+8(SP), AX
	ANDQ	$8, AX
	CMPQ	AX, $8
	SETEQ	"".~r2+24(SP)

With optimization using bitset:

	MOVQ	"".set+8(SP), AX
	BTL	$3, AX
	SETCS	"".~r2+24(SP)

output less than 1 instruction.

However, there is no speed improvement:

name         old time/op  new time/op  delta
AllBitSet-8  0.35ns ± 0%  0.35ns ± 0%   ~     (all equal)

Fixes #31904

Change-Id: I5dca4e410bf45716ed2145e3473979ec997e35d4
Reviewed-on: https://go-review.googlesource.com/c/go/+/175957
Run-TryBot: Brad Fitzpatrick <bradfitz@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Keith Randall <khr@golang.org>

The decoder called this function to check numbers being decoded into a
json.Number. However, these can't be quoted as strings, so the tokenizer
has already verified they are valid JSON numbers.

Verified this by adding a test with such an input. As expected, it
produces a syntax error, not the fmt.Errorf - that line could never
execute.

Since the only remaining non-test caller of isvalidnumber is in
encode.go, move the function there.

This change should slightly reduce the amount of work when decoding into
json.Number, though that isn't very common nor part of any current
benchmarks.

Change-Id: I67a1723deb3d18d5b542d6dd35f3ae56a43f23eb
Reviewed-on: https://go-review.googlesource.com/c/go/+/184817
Run-TryBot: Daniel Martí <mvdan@mvdan.cc>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>

There is an unnecessary lower operation in isJSType.
Simple logic fix can improve tiny performance.

name        old time/op    new time/op    delta
isJSType-8     152ns ± 0%      58ns ± 7%   -61.82%  (p=0.001 n=6+8)

name        old alloc/op   new alloc/op   delta
isJSType-8     32.0B ± 0%      0.0B       -100.00%  (p=0.000 n=8+8)

name        old allocs/op  new allocs/op  delta
isJSType-8      1.00 ± 0%      0.00       -100.00%  (p=0.000 n=8+8)

Change-Id: I281aadf1677d4377920c9649af206381189a27e6
Reviewed-on: https://go-review.googlesource.com/c/go/+/177118
Run-TryBot: Daniel Martí <mvdan@mvdan.cc>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Daniel Martí <mvdan@mvdan.cc>

This reverts https://golang.org/cl/185080.

Reason for revert: some new changes are erroring again, so this broke the builders.

Change-Id: I28da16da98b90cefbb47173d31bbbb56e43062d5
Reviewed-on: https://go-review.googlesource.com/c/go/+/191781
Run-TryBot: Daniel Martí <mvdan@mvdan.cc>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Emmanuel Odeke <emm.odeke@gmail.com>

state and ssafn both have their own Fatalf, so use them instead of
global Fatalf.

Updates #19683

Change-Id: Ie02a961d4285ab0a3f3b8d889a5b498d926ed567
Reviewed-on: https://go-review.googlesource.com/c/go/+/188539
Run-TryBot: Brad Fitzpatrick <bradfitz@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Keith Randall <khr@golang.org>

First, add cpu and memory profiling flags, as these are useful to see
where rulegen is spending its time. It now takes many seconds to run on
a recent laptop, so we have to keep an eye on what it's doing.

Second, stop writing '_ = var' lines to keep imports and variables used
at all times. Now that rulegen removes all such unused names, they're
unnecessary.

To perform the removal, lean on go/types to first detect what names are
unused. We can configure it to give us all the type-checking errors in a
file, so we can collect all "declared but not used" errors in a single
pass.

We then use astutil.Apply to remove the relevant nodes based on the line
information from each unused error. This allows us to apply the changes
without having to do extra parser+printer roundtrips to plaintext, which
are far too expensive.

We need to do multiple such passes, as removing an unused variable
declaration might then make another declaration unused. Two passes are
enough to clean every file at the moment, so add a limit of three passes
for now to avoid eating cpu uncontrollably by accident.

The resulting performance of the changes above is a ~30% loss across the
table, since go/types is fairly expensive. The numbers were obtained
with 'benchcmd Rulegen go run *.go', which involves compiling rulegen
itself, but that seems reflective of how the program is used.

	name     old time/op         new time/op         delta
	Rulegen          5.61s ± 0%          7.36s ± 0%  +31.17%  (p=0.016 n=5+4)

	name     old user-time/op    new user-time/op    delta
	Rulegen          7.20s ± 1%          9.92s ± 1%  +37.76%  (p=0.016 n=5+4)

	name     old sys-time/op     new sys-time/op     delta
	Rulegen          135ms ±19%          169ms ±17%  +25.66%  (p=0.032 n=5+5)

	name     old peak-RSS-bytes  new peak-RSS-bytes  delta
	Rulegen         71.0MB ± 2%         85.6MB ± 2%  +20.56%  (p=0.008 n=5+5)

We can live with a bit more resource usage, but the time/op getting
close to 10s isn't good. To win that back, introduce concurrency in
main.go. This further increases resource usage a bit, but the real time
on this quad-core laptop is greatly reduced. The final benchstat is as
follows:

	name     old time/op         new time/op         delta
	Rulegen          5.61s ± 0%          3.97s ± 1%   -29.26%  (p=0.008 n=5+5)

	name     old user-time/op    new user-time/op    delta
	Rulegen          7.20s ± 1%         13.91s ± 1%   +93.09%  (p=0.008 n=5+5)

	name     old sys-time/op     new sys-time/op     delta
	Rulegen          135ms ±19%          269ms ± 9%   +99.17%  (p=0.008 n=5+5)

	name     old peak-RSS-bytes  new peak-RSS-bytes  delta
	Rulegen         71.0MB ± 2%        226.3MB ± 1%  +218.72%  (p=0.008 n=5+5)

It might be possible to reduce the cpu or memory usage in the future,
such as configuring go/types to do less work, or taking shortcuts to
avoid having to run it many times. For now, ~2x cpu and ~4x memory usage
seems like a fair trade for a faster and better rulegen.

Finally, we can remove the old code that tried to remove some unused
variables in a hacky and unmaintainable way.

Change-Id: Iff9e83e3f253babf5a1bd48cc993033b8550cee6
Reviewed-on: https://go-review.googlesource.com/c/go/+/189798
Run-TryBot: Daniel Martí <mvdan@mvdan.cc>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Keith Randall <khr@golang.org>

This removes a special case that was added to fix issue #10956, but that
was never actually effective. The code in the test case still fails to
read, so perhaps the zip64 support added in CL 6463050 inadvertently
caught this particular case.

It's possible that the original theorized bug still exists, but I'm not
convinced it was ever fixed.

Update #28700

Change-Id: I4854de616364510f64a6def30b308686563f8dbb
Reviewed-on: https://go-review.googlesource.com/c/go/+/179757
Run-TryBot: Brad Fitzpatrick <bradfitz@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>

Template.New calls t.init, which allocates several items that
are immediately rewritten by copy, so avoid the call to New

Change-Id: I16c7cb001bbcd14cf547c1a2db2734a2f8214e7e
Reviewed-on: https://go-review.googlesource.com/c/go/+/182757
Run-TryBot: Daniel Martí <mvdan@mvdan.cc>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Daniel Martí <mvdan@mvdan.cc>

The TestParseErrors test function was not strict with unwanted errors
received from url.Parse(). It was not failing in such cases, now it does.

Change-Id: I18a26a68c1136f5c762989a76e04b47e33dd35f1
GitHub-Last-Rev: c33f9842f7908f27012859e25caa79388cc2785a
GitHub-Pull-Request: golang/go#32954
Reviewed-on: https://go-review.googlesource.com/c/go/+/185080Reviewed-by: Emmanuel Odeke <emm.odeke@gmail.com>
Run-TryBot: Emmanuel Odeke <emm.odeke@gmail.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>

TransmitFile does not allow for number of bytes that can be
transmitted to be larger than 2147483646. See

https://docs.microsoft.com/en-us/windows/win32/api/mswsock/nf-mswsock-transmitfile

for details. So adjust sendFile accordingly.

No test added, because this would require creating large file
(more than 2GB file).

Fixes #33193.

Change-Id: I82e0cb104d112264e4ea363bb20b6d02ac30b38e
Reviewed-on: https://go-review.googlesource.com/c/go/+/187037
Run-TryBot: Alex Brainman <alex.brainman@gmail.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Emmanuel Odeke <emm.odeke@gmail.com>

After Go.1.10+ strings.Builder is known as more efficient in
concatenating and building strings than bytes.Buffer.

In this CL,
there is a minor logic fix for getting advantage of strings.builder.

name               old time/op    new time/op    delta
DefinedTemplate-8     543ns ± 3%     512ns ± 2%   -5.73%  (p=0.000 n=8+8)

name               old alloc/op   new alloc/op   delta
DefinedTemplate-8      192B ± 0%      160B ± 0%  -16.67%  (p=0.000 n=8+8)

name               old allocs/op  new allocs/op  delta
DefinedTemplate-8      5.00 ± 0%      5.00 ± 0%     ~     (all equal)

Change-Id: Icda0054d146e6c5e32ed8a4d13221bb6850d31b4
Reviewed-on: https://go-review.googlesource.com/c/go/+/175261
Run-TryBot: Emmanuel Odeke <emm.odeke@gmail.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Emmanuel Odeke <emm.odeke@gmail.com>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>

Add brief descriptions of why one might implement
an Is or As method.

Fixes #33364.

Change-Id: I81a091bf564c654ddb9ef3997e780451a01efb7a
Reviewed-on: https://go-review.googlesource.com/c/go/+/191338Reviewed-by: Emmanuel Odeke <emm.odeke@gmail.com>
Reviewed-by: Andrew Bonventre <andybons@golang.org>
Run-TryBot: Jonathan Amsterdam <jba@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>

Because TestUnmarshal actually allocates a new value to decode into
using ptr's pointer type, any existing data is thrown away. This was
harmless in alomst all of the test cases, minus the "overwriting of
data" ones added in 2015 in CL 12209.

I spotted that nothing covered decoding a JSON array with few elements
into a slice which already had many elements. I initially assumed that
the code was buggy or that some code could be removed, when in fact
there simply wasn't any code covering the edge case.

Move those two tests to TestPrefilled, which already served a very
similar purpose. Remove the map case, as TestPrefilled already has
plenty of prefilled map cases. Moreover, we no longer reset an entire
map when decoding, as per the godoc:

	To unmarshal a JSON object into a map, Unmarshal first
	establishes a map to use. If the map is nil, Unmarshal allocates
	a new map. Otherwise Unmarshal reuses the existing map, keeping
	existing entries.

Finally, to ensure that ptr is used correctly in the future, make
TestUnmarshal error if it's anything other than a pointer to a zero
value. That is, the only correct use should be new(type). Don't rename
the ptr field, as that would be extremely noisy and cause unwanted merge
conflicts.

Change-Id: I41e3ecfeae42d877ac5443a6bd622ac3d6c8120c
Reviewed-on: https://go-review.googlesource.com/c/go/+/185738
Run-TryBot: Daniel Martí <mvdan@mvdan.cc>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Emmanuel Odeke <emm.odeke@gmail.com>

rulegen.go produces plaintext Go code directly, which was fine for a
while. However, that's started being a bottleneck for making code
generation more complex, as we can only generate code directly one line
at a time.

Some workarounds were used, like multiple layers of buffers to generate
chunks of code, to then use strings.Contains to see whether variables
need to be defined or not. However, that's error-prone, verbose, and
difficult to work with.

A better approach is to generate an intermediate syntax tree in memory,
which we can inspect and modify easily. For example, we could run a
number of "passes" on the syntax tree before writing to disk, such as
removing unused variables, simplifying logic, or moving declarations
closer to their uses.

This is the first step in that direction, without changing any of the
generated code. We didn't use go/ast directly, as it's too complex for
our needs. In particular, we only need a few kinds of simple statements,
but we do want to support arbitrary expressions. As such, define a
simple set of statement structs, and add thin layers for printer.Fprint
and ast.Inspect.

A nice side effect of this change, besides removing some buffers and
string handling, is that we can now avoid passing so many parameters
around. And, while we add over a hundred lines of code, the tricky
pieces of code are now a bit simpler to follow.

While at it, apply some cleanups, such as replacing isVariable with
token.IsIdentifier, and consistently using log.Fatalf.

Follow-up CLs will start improving the generated code, also simplifying
the rulegen code itself. I've added some TODOs for the low-hanging fruit
that I intend to work on right after.

Updates #30810.

Change-Id: Ic371c192b29c85dfc4a001be7fbcbeec85facc9d
Reviewed-on: https://go-review.googlesource.com/c/go/+/177539
Run-TryBot: Daniel Martí <mvdan@mvdan.cc>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Keith Randall <khr@golang.org>

HTTP is an initialism, not an acronym, where you pronounce each letter as a
word. It's "an H", not "a H".

Running `find src/net/http -type f | xargs grep -n 'an HTTP' | wc -l` shows
that the "an HTTP" form is used 67 times across the `net/http` package.
Furthermore, `find src/net/http -type f | xargs grep -n 'a HTTP' | wc -l`
yields only 4 results.

Change-Id: I219c292a9e2c9bf7a009dbfe82ea8b15874685e9
GitHub-Last-Rev: 6ebd095023af47444b6b0fc5b6d7b26d85f4c7b7
GitHub-Pull-Request: golang/go#33810
Reviewed-on: https://go-review.googlesource.com/c/go/+/191700Reviewed-by: Toshihiro Shiino <shiino.toshihiro@gmail.com>
Reviewed-by: Ian Lance Taylor <iant@golang.org>

After golang.org/cl/33895, function adjustctx can not be inlined,
cost 82 exceeds budget 80

Change-Id: Ie559ed80ea2c251add940a99f11b2983f6cbddbc
Reviewed-on: https://go-review.googlesource.com/c/go/+/187977
Run-TryBot: Cuong Manh Le <cuong.manhle.vn@gmail.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Keith Randall <khr@golang.org>

Array accesses with index types smaller than the machine word size may
involve a sign or zero extension of the index value before bounds
checking. Currently, this defeats prove because the facts about the
original index value don't flow through the sign/zero extension.

This CL fixes this by looking back through value-preserving sign/zero
extensions when adding facts via Update and, where appropriate, applying
the same facts using the pre-extension value. This fix is enhanced by
also looking back through value-preserving extensions within
ft.isNonNegative to infer whether the extended value is known to be
non-negative. Without this additional isNonNegative enhancement, this
logic is rendered significantly less effective by the limitation
discussed in the next paragraph.

In Update, the application of facts to pre-extension values is limited
to cases where the domain of the new fact is consistent with the type of
the pre-extension value. There may be cases where this cross-domain
passing of facts is valid, but distinguishing them from the invalid
cases is difficult for me to reason about and to implement.
Assessing which cases to allow requires details about the context and
inferences behind the fact being applied which are not available
within Update. Additional difficulty arises from the fact that the SSA
does not curently differentiate extensions added by the compiler for
indexing operations, extensions added by the compiler for implicit
conversions, or explicit extensions from the source.

Examples of some cases that would need to be filtered correctly for
cross-domain facts:

(1) A uint8 is zero-extended to int for indexing (a value-preserving
zeroExt). When, if ever, can signed domain facts learned about the int be
applied to the uint8?

(2) An int8 is sign-extended to int16 (value-preserving) for an equality
comparison. Equality comparison facts are currently always learned in both
the signed and unsigned domains. When, if ever, can the unsigned facts
learned about the int16, from the int16 != int16 comparison, be applied
to the original int8?

This is an alternative to CL 122695 and CL 174309. Compared to CL 122695,
this CL differs in that the facts added about the pre-extension value will
pass through the Update method, where additional inferences are processed
(e.g. fence-post implications, see #29964). CL 174309 is limited to bounds
checks, so is narrower in application, and makes the code harder to read.

Fixes #26292.
Fixes #29964.
Fixes #15074

Removes 238 bounds checks from std/cmd.

Change-Id: I1f87c32ee672bfb8be397b27eab7a4c2f304893f
Reviewed-on: https://go-review.googlesource.com/c/go/+/174704
Run-TryBot: Zach Jones <zachj1@gmail.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Giovanni Bajo <rasky@develer.com>

directlyAssignable invoked rtype.Name() just to compare its result
to empty string. We really only need to check whether rtype has
name. It can be done much cheaper, by checking tflagNamed.

Benchmark: https://play.golang.org/p/V2BzESPuf2w
name                   old time/op  new time/op  delta
DirectlyAssignable-12  32.7ns ± 6%   6.6ns ± 6%  -79.80%  (p=0.008 n=5+5)

Fixes #32186

Change-Id: I1a2a167dbfddf319fba3015cb6a011bf010f99a8
Reviewed-on: https://go-review.googlesource.com/c/go/+/178518
Run-TryBot: Brad Fitzpatrick <bradfitz@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>

Don't skip closing parentheses of any kind after a missing
expression. They are likely part of the lexical construct
enclosing the expression.

Fixes #33386.

Change-Id: Ic0abc2037ec339a345ec357ccc724b7ad2a64c00
Reviewed-on: https://go-review.googlesource.com/c/go/+/188502Reviewed-by: Matthew Dempsky <mdempsky@google.com>

Some constants were added above the initial copyright blurb, and then
later a new copyright blurb was added on top of that. So we wound up
with two header sections, one of which contained a useful comment that
became obscured. This commit fixes up that mistake.

Change-Id: I8b9b8c34495cdceae959e151e8ccdee3137f6ca4
Reviewed-on: https://go-review.googlesource.com/c/go/+/191841
Run-TryBot: Jason A. Donenfeld <Jason@zx2c4.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Ian Lance Taylor <iant@golang.org>

Quietly drop duplicate methods inherited from embedded interfaces if
they have an identical signature to existing methods.

Updates #6977.

Change-Id: I144151cb7d99695f12b555c0db56207993c56284
Reviewed-on: https://go-review.googlesource.com/c/go/+/187519
Run-TryBot: Matthew Dempsky <mdempsky@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Robert Griesemer <gri@golang.org>

Move checkdupfields call into expandiface, and inline/simplify offmod.
More prep work for implementing #6977.

Change-Id: I958ae87f761ec25a8fa7298a2a3019eeca5b25ba
Reviewed-on: https://go-review.googlesource.com/c/go/+/187518Reviewed-by: Robert Griesemer <gri@golang.org>

Allows avoiding the Type.Fields call, which affects prevents
checkdupfields from being called at the more natural point during
dowidth.

Change-Id: I724789c860e7fffba1e8e876e2d74dcfba85d75c
Reviewed-on: https://go-review.googlesource.com/c/go/+/187517Reviewed-by: Robert Griesemer <gri@golang.org>
Run-TryBot: Robert Griesemer <gri@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>

Updates #33738

Change-Id: If0856d7c57ecfde08341c1aecb5e92361fd64f2b
Reviewed-on: https://go-review.googlesource.com/c/go/+/191217Reviewed-by: Andrew Bonventre <andybons@golang.org>
Run-TryBot: Andrew Bonventre <andybons@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>

Fixes #33796

Change-Id: I9f6837be96410e96d004523c48bef95ee1427484
Reviewed-on: https://go-review.googlesource.com/c/go/+/191746Reviewed-by: Bryan C. Mills <bcmills@google.com>

The stack of delayed actions is grown by pushing a new action
on top with Checker.later. Checker.processDelayed processes
all actions above a top watermark and then resets the stack
to top.

Until now, pushed actions above the watermark were processed
in LIFO order. This change processes them in FIFO order, which
seems more natural (if an action A was delayed before an action
B, A should be processed before B for that stack segment).

(With this change, Checker.later could be used instead of
Checker.atEnd to postpone interface method type comparison
and then the specific example in issue #33656 does type-check.
However, in general we want interface method type comparisons
to run after all interfaces are completed. With Checker.later
we may still end up mixing interface completions and interface
method type comparisons in ways leading to other errors for
sufficiently convoluted code.)

Also, move Checker.processDelayed from resolver.go to check.go.

Change-Id: Id31254605e6944c490eab410553fff907630cc64
Reviewed-on: https://go-review.googlesource.com/c/go/+/191458Reviewed-by: Matthew Dempsky <mdempsky@google.com>

Updates #6977.

Change-Id: I6eda4be550e7c7ea1e1bac3222850002d90a81a8
Reviewed-on: https://go-review.googlesource.com/c/go/+/190378Reviewed-by: Rob Pike <r@golang.org>
Reviewed-by: Matthew Dempsky <mdempsky@google.com>

Introduce a new list of final actions that is executed at the
end of type checking and use it to collect method type comparisons
and also map key checks.

Fixes #33656.

Change-Id: Ia77a35a45a9d7eaa7fc3e9e19f41f32dcd6ef9d9
Reviewed-on: https://go-review.googlesource.com/c/go/+/191418Reviewed-by: Alan Donovan <adonovan@google.com>

When creating a new interface via the exported API calls, a shared
empty and completed Interface value is returned if there are no
methods or embedded interfaces. This is a minor optimization and
matches the internal behavior when creating empty interfaces.

Since calling Interface.Complete is idempotent, and since there
are no other legitimate ways to create Interface values externally
but via NewInterface/NewInterfaceType calls, and completed Interfaces
are considered "immutable", this change is not expected to affect
clients. The only observable behavior that changed is the string
value for empty interfaces created via the above API calls; those
empty interfaces now don't show "incomplete" anymore even before
Interface.Complete is called. Except in special test cases, this
behavior is unlikely to affect clients.

Change-Id: Idf7f2cd112241c5b81a43b4544bbe3f2e003d8d8
Reviewed-on: https://go-review.googlesource.com/c/go/+/191417Reviewed-by: Matthew Dempsky <mdempsky@google.com>