Also: report language version (plus date) in spec header.
Fixes#65137.
Change-Id: I4f1d220d5922c40a36264df2d0a7bb7cd0756bac
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Follow-up on CL 551095.
For #56010.
Change-Id: I8913d6ca96c419c81683e88c6286b05ae1323416
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For #56010.
Change-Id: Icca987a03d80587dd0e901f596ff7788584893ed
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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
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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 is partly based on CL 510535.
For #61405.
Change-Id: Ic94f6726f9eb34313f11bec7b651921d7e5c18d4
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Fixes#63525.
Change-Id: Ie9aa4dd47c025cd593e576c6e8de1774e1d1e302
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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
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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
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Change-Id: I40595a3f598483d029473af465c756f8777ecc91
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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
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Change-Id: I06345199ff16c80be83c345d734caef1714ec089
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Change-Id: I0d4ccbc396c48d565c0cbe93c9558ab330a44d02
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This leaves the specific unification details out in favor
of a (forthcoming) section in an appendix.
Change-Id: If984c48bdf71c278e1a2759f9a18c51ef58df999
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Change-Id: I9cdb301163b67add39928c8fc7df2b7f3893f45e
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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
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Per feedback on #56351.
For #56351.
Change-Id: I63dd1713a1efe4d7180d932dbd8e1510cbb32e90
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Change-Id: I9f008dba7ba6e30f0e62647482a3ed0b51bc1ad0
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Fixes#60731.
Change-Id: I71fad1c8385b13d036bb0ce7ae6bd21e0f596e51
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For #57411.
Change-Id: I94982d939d16ad17174f801cc167cc10ddc8da30
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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
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Fixes#60570.
Change-Id: I7ef834731ea26ceee5ec9b7438fdd8323aaf828e
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For #59488.
Change-Id: I50f65216bf02b42c1e0619702833f4a6dbed8925
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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
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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: ed5aaf9d02
GitHub-Pull-Request: golang/go#59626
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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
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Fixes#59506
Change-Id: I2f8b92e93b706b061ca0eb0bd52e5cf798ce9ede
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The typechecker already enforces this semantic, but the spec is not
updated when unsafe.{SliceData,String,StringData} were added.
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Change-Id: I5e3aca2b8fc78f38c9e2cdc67adf86d57ac85b1c
GitHub-Last-Rev: 0e5ddffe33
GitHub-Pull-Request: golang/go#58353
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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.
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Fixes#40882.
Change-Id: I90f99d75e6d66f857b6ab8789c6d436f85d20993
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For #56548.
Fixes#57012.
Change-Id: I44f850522e52b1811025fb31bcef289da8f8089d
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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
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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.
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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
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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
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For #53003.
Change-Id: If5d76c7b8dfcbcab919cad9c333c0225fc155859
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Fixes#8606.
Change-Id: I64b13b2ed61ecae4641264deb47c9f7653a80356
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Converting from nil slice to zero element array is ok, so explicitly
describe the behavior in the spec.
For #46505
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For #46505.
Change-Id: I1a30fd895496befd16626afb48717ac837ed5778
Reviewed-on: https://go-review.googlesource.com/c/go/+/429315
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