Add a new section to the Appendix describing what features were
changed or added in which language version.
Add short links with references to the required language version
where relevant.
Fixes#63857.
Change-Id: I5250f856d8688a71602076fcc662aa678d96a5d2
Reviewed-on: https://go-review.googlesource.com/c/go/+/549518
Reviewed-by: Robert Griesemer <gri@google.com>
Reviewed-by: Rob Pike <r@golang.org>
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The valid conversions consider the core types of operands, not just
their underlying type.
This also explains the valid arguments for unsafe.Slice which are
explained in terms of unsafe.Pointer conversions.
unsafe.SliceData simply refers to "slice argument" and we use
similar terminology elsewhere in the spec to denote values that
have a core type of slice (or any other type for that matter).
Leaving alone for now.
Fixes#64452.
Change-Id: I0eed3abbc0606f22358835e5d434f026fe0909c8
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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
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Reviewed-by: Ian Lance Taylor <iant@golang.org>
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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
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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
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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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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
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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
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"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: ed5aaf9d02c294e87688066f6218e5d58b0f62bf
GitHub-Pull-Request: golang/go#59626
Reviewed-on: https://go-review.googlesource.com/c/go/+/484576
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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: 8acdb60d6e255f73fdeb908d2540d4ee35db3fd7
GitHub-Pull-Request: golang/go#59528
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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
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- 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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