Adds:
GOEXPERIMENT=loopvar (expected way of invoking)
-d=loopvar={-1,0,1,2,11,12} (for per-package control and/or logging)
-d=loopvarhash=... (for hash debugging)
loopvar=11,12 are for testing, benchmarking, and debugging.
If enabled,for loops of the form `for x,y := range thing`, if x and/or
y are addressed or captured by a closure, are transformed by renaming
x/y to a temporary and prepending an assignment to the body of the
loop x := tmp_x. This changes the loop semantics by making each
iteration's instance of x be distinct from the others (currently they
are all aliased, and when this matters, it is almost always a bug).
3-range with captured iteration variables are also transformed,
though it is a more complex transformation.
"Optimized" to do a simpler transformation for
3-clause for where the increment is empty.
(Prior optimization of address-taking under Return disabled, because
it was incorrect; returns can have loops for children. Restored in
a later CL.)
Includes support for -d=loopvarhash=<binary string> intended for use
with hash search and GOCOMPILEDEBUG=loopvarhash=<binary string>
(use `gossahash -e loopvarhash command-that-fails`).
Minor feature upgrades to hash-triggered features; clients can specify
that file-position hashes use only the most-inline position, and/or that
they use only the basenames of source files (not the full directory path).
Most-inlined is the right choice for debugging loop-iteration change
once the semantics are linked to the package across inlining; basename-only
makes it tractable to write tests (which, otherwise, depend on the full
pathname of the source file and thus vary).
Updates #57969.
Change-Id: I180a51a3f8d4173f6210c861f10de23de8a1b1db
Reviewed-on: https://go-review.googlesource.com/c/go/+/411904
Reviewed-by: Matthew Dempsky <mdempsky@google.com>
Run-TryBot: David Chase <drchase@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org>
The test directory contains tests of the Go tool chain and runtime.
It includes black box tests, regression tests, and error output tests.
They are run as part of all.bash.
To run just these tests, execute:
../bin/go test internal/testdir
To run just tests from specified files in this directory, execute:
../bin/go test internal/testdir -run='Test/(file1.go|file2.go|...)'
Standard library tests should be written as regular Go tests in the appropriate package.
The tool chain and runtime also have regular Go tests in their packages.
The main reasons to add a new test to this directory are:
it is most naturally expressed using the test runner; or
it is also applicable to gccgo and other Go tool chains.
