This change in terminology prevents potential confusion
that migth be caused by associating "structural type"
with "structural typing"; the two are not connected.
Also, adjusted introductory paragraph of section on
constraint type inference: type inference goes in both
directions, from type parameter to core type and vice
versa. The previous description was not quite accurate.
Change-Id: If4ca300f525eea660f68486302619aa6ad5dbc2c
Reviewed-on: https://go-review.googlesource.com/c/go/+/384238
Trust: Robert Griesemer <gri@golang.org>
Reviewed-by: Ian Lance Taylor <iant@golang.org>
The terms "integer type", "floating-point type", and "complex type"
are used frequently in the spec but are not explicitly (only indirectly)
defined.
Slightly rephrased the section on numeric types and introduce these
terms explicitly. Add links to this section.
Change-Id: I3fb888933bece047da8b356b684c855618e9aee4
Reviewed-on: https://go-review.googlesource.com/c/go/+/384157
Trust: Robert Griesemer <gri@golang.org>
Reviewed-by: Ian Lance Taylor <iant@golang.org>
Change-Id: Ic338788d6410ed0d09ad129811377ee9ce5ed496
Reviewed-on: https://go-review.googlesource.com/c/go/+/367954
Trust: Robert Griesemer <gri@golang.org>
Reviewed-by: Ian Lance Taylor <iant@golang.org>
This reverts CL 380854.
Per the conluding discussions on #50791. A follow-up will
document `comparable` more thoroughly.
For #50791.
Change-Id: I15db9051784a012f713e28d725c3b8bbfeb40569
Reviewed-on: https://go-review.googlesource.com/c/go/+/381076
Trust: Robert Griesemer <gri@golang.org>
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Mostly from CL 367954.
Change-Id: Id003b0f785a286a1a649e4d6e8c87d0418a36545
Reviewed-on: https://go-review.googlesource.com/c/go/+/379920
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Introduce a (local) notion of a set of representative types,
which serves as a representation/approximation of an
interface's actual type set. If the set of representative
types is is non-empty and finite, it corresponds to the set
of specific types of the interface.
In the implementation, the set of representative types serves
as a finite representation of an interface's type set, together
with the set of methods.
Change-Id: Ib4c6cd5e17b81197672e4247be9737dd2cb6b56f
Reviewed-on: https://go-review.googlesource.com/c/go/+/376834
Trust: Robert Griesemer <gri@golang.org>
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Problem pointed out on golang-nuts mailing list.
Change-Id: If1c9b22e1ed7b4ec7ebcaadc80fa450333e6856c
Reviewed-on: https://go-review.googlesource.com/c/go/+/375799
Trust: Robert Griesemer <gri@golang.org>
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The new description matches the implementation (CL 370774).
Also, in the section on type constraints, use "defines" instead of
"determines" because the constraint interface defines the type set
which is precisely the set of acceptable type arguments.
For #49482.
Change-Id: I6f30f49100e8ba8bec0a0f1b450f88cae54312eb
Reviewed-on: https://go-review.googlesource.com/c/go/+/372874
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For #49602.
Change-Id: I0d3ff8f087dffb3409918494147fd1dceff7514d
Reviewed-on: https://go-review.googlesource.com/c/go/+/372694
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As written, the conversion P(x), where P and the type
of x are type parameters with identical underlying types
(i.e., identical constraints), is valid. However, unless
the type of x and P are identical (which is covered with
the assignability rule), such a conversion is not valid
in general (consider the case where both type parameters
are different type parameters with constraint "any").
This change adjusts the rules to prohibit type parameters
in this case. The same reasoning applies and the analogue
change is made for pointer types.
The type checker already implements these updated rules.
Change-Id: Id90187900cb2820f6a0a0cf582cf26cdf8addbce
Reviewed-on: https://go-review.googlesource.com/c/go/+/371074
Trust: Robert Griesemer <gri@golang.org>
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Change-Id: I562d4648756e710020ee491f3801896563a89baa
Reviewed-on: https://go-review.googlesource.com/c/go/+/367395
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We want to support some special cases for index expressions, len, and
cap on operands of type parameters (such as indexing a value constrained
by byte slices and strings), hence the extra rules.
Change-Id: I4a07dc7e64bb47361b021d606c52eae1784d5430
Reviewed-on: https://go-review.googlesource.com/c/go/+/366814
Trust: Robert Griesemer <gri@golang.org>
Trust: Dan Scales <danscales@google.com>
Reviewed-by: Dan Scales <danscales@google.com>
- fix definition of "specific types" and add more examples
- state that a parameterized function must be instantiated
when used as a function value
- remove duplicate word ("can can" -> "can")
Thanks to @danscales for finding these.
Change-Id: Ideb41efc35a3e67694d3bc97e462454feae37c44
Reviewed-on: https://go-review.googlesource.com/c/go/+/367394
Trust: Robert Griesemer <gri@golang.org>
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Reviewed-by: Dan Scales <danscales@google.com>
This change corrects the link `Instantiantions` to `Instantiations` in the spec.
Change-Id: Ib0ed03420ae401d20af1ea723c5487018b2f462d
GitHub-Last-Rev: b84316c818
GitHub-Pull-Request: golang/go#49816
Reviewed-on: https://go-review.googlesource.com/c/go/+/367274
Reviewed-by: Ian Lance Taylor <iant@golang.org>
Reviewed-by: Emmanuel Odeke <emmanuel@orijtech.com>
Change-Id: I11111b3617673be94508128489aed6488d518537
Reviewed-on: https://go-review.googlesource.com/c/go/+/366834
Trust: Robert Griesemer <gri@golang.org>
Reviewed-by: Ian Lance Taylor <iant@golang.org>
Change-Id: I5ffc7f26236487070447eaa0f6b14d1fab44c3c7
Reviewed-on: https://go-review.googlesource.com/c/go/+/366794
Trust: Robert Griesemer <gri@golang.org>
Reviewed-by: Ian Lance Taylor <iant@golang.org>
Change-Id: I2770da87b4c977b51dfa046f2f08283917675e1c
Reviewed-on: https://go-review.googlesource.com/c/go/+/365916
Trust: Robert Griesemer <gri@golang.org>
Trust: Dan Scales <danscales@google.com>
Reviewed-by: Ian Lance Taylor <iant@golang.org>
Reviewed-by: Dan Scales <danscales@google.com>
Change-Id: I7bfddf4be0d1d95419f312bb349ae2e16b74b795
Reviewed-on: https://go-review.googlesource.com/c/go/+/365915
Trust: Robert Griesemer <gri@golang.org>
Reviewed-by: Ian Lance Taylor <iant@golang.org>
Change-Id: I3c4d8bdb5e92ee7fdca9593fb043f94f467755e8
Reviewed-on: https://go-review.googlesource.com/c/go/+/365434
Trust: Robert Griesemer <gri@golang.org>
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Change-Id: I4423a059527066c4418c195911f8184dfd3f5a15
Reviewed-on: https://go-review.googlesource.com/c/go/+/365914
Trust: Robert Griesemer <gri@golang.org>
Reviewed-by: Ian Lance Taylor <iant@golang.org>
The notion of specific types will be used to define rules for
assignability, convertability, etc. when type parameters are
involved.
Change-Id: Ic5c134261e2a9fe05cdf25efd342f052458ab5c8
Reviewed-on: https://go-review.googlesource.com/c/go/+/366754
Trust: Robert Griesemer <gri@golang.org>
Reviewed-by: Ian Lance Taylor <iant@golang.org>
Thanks to @danscales for noticing the mistake.
Change-Id: I547ee80a78419765b82d39d7b34dc8d3bf962c35
Reviewed-on: https://go-review.googlesource.com/c/go/+/366215
Trust: Robert Griesemer <gri@golang.org>
Reviewed-by: Ian Lance Taylor <iant@golang.org>
Reviewed-by: Dan Scales <danscales@google.com>
This change introduces the notion of a structural interface
and its corresponding structural type.
Change-Id: Ib5442dfd04cb5950b4467428cae51849f8922272
Reviewed-on: https://go-review.googlesource.com/c/go/+/365474
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- add section on type parameters
- added two sections on the scope of type parameters
- expanded general section on types accordingly
- introduced the notion of a named type which will
help in simplifying various rules (subsequent CLs)
Change-Id: I49c1ed7d6d4f951d751f0a3ca5dfb637e49829f2
Reviewed-on: https://go-review.googlesource.com/c/go/+/365414
Trust: Robert Griesemer <gri@golang.org>
Reviewed-by: Ian Lance Taylor <iant@golang.org>
Change-Id: I29e9188a0fa1326c2755a9b86aeb47feaa8019be
Reviewed-on: https://go-review.googlesource.com/c/go/+/365274
Trust: Robert Griesemer <gri@golang.org>
Reviewed-by: Ian Lance Taylor <iant@golang.org>
- fixed a typo in the method set section
- express in the syntax that ~T denotes an underlying type
- be more precise when talking about types vs type terms
- refer to "unions" rather than "union expressions"
- make it clear in the spec title that this is WIP
Change-Id: I9b2c4b1f77bc50dd574ed6893bedd40529c320fc
Reviewed-on: https://go-review.googlesource.com/c/go/+/365154
Trust: Robert Griesemer <gri@golang.org>
Reviewed-by: Ian Lance Taylor <iant@golang.org>
This is the first of several CLs that update the existing
Go 1.17 spec for type parameters.
This CL updates the section on method sets and interface types.
It also adds "any", "comparable" to the list of predeclared
identifiers.
Change-Id: I0ce25dc02791c33150c0d949528512610faf3eab
Reviewed-on: https://go-review.googlesource.com/c/go/+/362999
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Thanks for jtagcat@ for finding this.
Change-Id: If7324808edbae19ec8bf503b04e0426f3fb3b47a
Reviewed-on: https://go-review.googlesource.com/c/go/+/363394
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Thanks to @bodar (Github) for finding this.
Fixes#48422.
Change-Id: I031c3d82a02db1d204e2b86b494d89784d37f073
Reviewed-on: https://go-review.googlesource.com/c/go/+/350409
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Reviewed-by: Matthew Dempsky <mdempsky@google.com>
CL 85215 added prose to provide some minimal intuition for the
definition of a "terminating statement". While the original definition
was perfectly fine, the added prose was actually incorrect: If the
terminating statement is a goto, it might jump to a labeled statement
following that goto in the same block (it could be the very next
statement), and thus a terminating statement does not in fact
"prevent execution of all statements that lexically appear after
it in the same block".
Rather than explaining the special case for gotos with targets that
are lexically following the goto in the same block, this CL opts for
a simpler approach.
Thanks to @3bodar (Github) for finding this.
Fixes#48323.
Change-Id: I8031346250341d038938a1ce6a75d3e687d32c37
Reviewed-on: https://go-review.googlesource.com/c/go/+/349172
Trust: Robert Griesemer <gri@golang.org>
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Reviewed-by: Matthew Dempsky <mdempsky@google.com>
Reviewed-by: Emmanuel Odeke <emmanuel@orijtech.com>
Reviewed-by: Rob Pike <r@golang.org>
Reviewed-by: Ian Lance Taylor <iant@golang.org>
So it's clear to the reader that if "M" is a promoted method from
embedded field "T", then "x.M" will be expanded to "x.T.M" during the
evaluation of the method value.
Fixes#47863
Change-Id: Id3b82127a2054584b6842c487f6e15c3102dc9fe
Reviewed-on: https://go-review.googlesource.com/c/go/+/344209
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There is an example for nil slice already, so adding example for non-nil
zero length slice, too, clarifying to the reader that the result is also
non-nil and different from nil slice case.
Updates #395
Change-Id: I019db1b1a1c0c621161ecaaacab5a4d888764b1a
Reviewed-on: https://go-review.googlesource.com/c/go/+/336890
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For #19367
Change-Id: If0ff8ddba3b6b48e2e198cf3653e73284c7572a3
Reviewed-on: https://go-review.googlesource.com/c/go/+/332409
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Reviewed-by: Keith Randall <khr@golang.org>
Add unsafe.Add and unsafe.Slice to the list of built-in functions
which are not permitted in statement context. The compiler and
type checker already enforce this restriction, this just fixes
a documentation oversight.
For #19367.
For #40481.
Change-Id: Iabc63a8db048eaf40a5f5b5573fdf00b79d54119
Reviewed-on: https://go-review.googlesource.com/c/go/+/329925
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The word "specifier" is used once only here and technically not defined.
Change-Id: Ifc9f0582f4eb3c3011ba60d8008234de511d4be6
Reviewed-on: https://go-review.googlesource.com/c/go/+/323730
Reviewed-by: Robert Griesemer <gri@golang.org>
Trust: Ian Lance Taylor <iant@golang.org>
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Replace "reserved word" by "keyword" as the latter is the official term.
Change-Id: I9f269759b872026034a9f47e4a761cff2d348ca0
Reviewed-on: https://go-review.googlesource.com/c/go/+/323729
Reviewed-by: Robert Griesemer <gri@golang.org>
Trust: Ian Lance Taylor <iant@golang.org>
Trust: Robert Griesemer <gri@golang.org>
1. The existing prose implied that a switch expression type must
be comparable because it is tested for equality against all case
expressions. But for an empty switch (no case expressions), it
was not clear if the switch expression needed to be comparable.
Require it to match the behavior of compiler and type checkers.
2. While making this change, remove redundant language explaining
what happens with untyped boolean switch expression values: the
default type of an untyped boolean value is bool, this is already
covered by the first part of the relevant sentence.
Fixes#43200.
Change-Id: Id8e0f29cfa8722b57cd2b7b58cba85b58c5f842b
Reviewed-on: https://go-review.googlesource.com/c/go/+/314411
Trust: Robert Griesemer <gri@golang.org>
Reviewed-by: Matthew Dempsky <mdempsky@google.com>
Reviewed-by: Rob Pike <r@golang.org>
