Use a single `SemIR::Function` per `Core` interface method, whether it's
generated locally or imported. This prevents generating duplicate
functions, which lead to different types when the witness appears in a
`FacetValue` as part of a specific for a class.
We use a `CanonicalValueStore` of `GeneratedFunction` objects that allow
finding an existing FunctionId for a `Generated` special function before
(re-)generating it. Mangling for `Generated` functions is also moved to
use the values from the `GeneratedFunction`'s canonicalization key, so
that we have a consistent source of truth for the unique ID of a
`Generated` function across all files.
New tests are in
`toolchain/check/testdata/impl/custom_witness/destroy.carbon`.
Implementing interface modifiers causes an infinite loop when generating
fingerprints because the witness value generates a fingerprint that's
dependent on something dependent on the witness value. We've debugged
this to the witness table's `elements_id` field.
This hack is a workaround for creating a new block type whose value is
not codependent with its identity.
Co-authored-by: Richard Smith <richard@metafoo.co.uk>
Co-authored-by: Richard Smith <richard@metafoo.co.uk>
During impl lookup, for each (generic) impl candidate, we form a
specific for that impl by deducing its generic arguments. Then we
compare the query interface against the impl's specific interface. That
comparison needs the deduced arguments applied to the impl's specific
interface. Previously we were doing this by getting the impl's
constraint facet type with the impl's specific applied (via
`GetConstantValueInSpecific()`) and then identifying that facet type
with the impl's deduced self.
Identify is a fairly expensive operation. It runs subst, trying to
replace `.Self` references. It walks named constraints. It collects
require declarations. We're looking at making it do _more_ in the future
too, including rewrite constraint resolution and collecting rewrite and
same-type constraints. For this reason we have a cache to make it cheap
on the second run, but it's still a very heavyweight operation to
involve in impl lookup, when all we want is to apply the impl's specific
to its target interface.
We almost have all the information we need to avoid the identification
step. We have the impl's specific after deduction. And we have the
SpecificInterface that the impl is targeting in the `Impl` struct. When
we form the specific for the impl itself, we resolve the declaration
block and form new constant values for all instructions in there, but
that does not cover the SpecificInterface that we're storing in the
`Impl` struct. So we add a new instruction to the impl's eval block,
which will be symbolic when the impl is generic and the target interface
depends on a generic parameter. And we store the `InstId` in the `Impl`
struct. This allows us to gets its constant value later with the impl's
specific applied. From that constant value we can then pull out the
SpecificInterface that the impl is targeting.
This adds SemIR structs and implements building `observe` lists, as well
as naming, formatting, and importing `observe` declarations.
---------
Co-authored-by: Dana Jansens <danakj@orodu.net>
The bulk of this change is changing most pattern insts to be `Always`
rather than `AlwaysUnique` constants, so that they can be wrapped in
`SpecificConstant`s to perform substitution. That then lets thunking
rely much more on `SpecificConstant` wrappers instead of deep-copying
the inst tree with modified types.
This approach to thunking should scale better, particularly as things
like form generics make function signatures more complex, because we can
leverage the existing support for constant evaluation and substitution.
Unfortunately, applying this approach to binding patterns will require
more work; see the TODO near the top of `thunk.cpp` for details.
---------
Co-authored-by: Richard Smith <richard@metafoo.co.uk>
Implements proposal #7016: `self` moves from the deduced implicit list
(`fn F[self: Self]()`) to the front of the explicit list. Its type may
be written explicitly (`fn F(self: Self)`) or omitted, in which case it
defaults to `Self` (`fn F(self)`, `fn F(ref self)`); `self` in the
implicit list is rejected.
Throughout checking, `self` is modeled as the first explicit parameter.
Because a method is just a function whose first parameter is `self`, it
can also be called as an ordinary function with the receiver passed
explicitly (`Type.M(obj, ...)`), not only as `obj.M(...)`. A new
`SemIR::CallArgParamPatterns` helper chooses the parameters matched
against the explicit arguments, excluding a leading `self` only when it
is supplied as a method-call receiver; arity checking, conversion, and
generic deduction use it. The resulting SemIR and lowering are
unchanged: `self` is still `call_param0`, and witnesses, thunks, and
vtables are unaffected.
An omitted `self` type is parsed as a `SelfBindingPattern` node with no
type expression; checking synthesizes the `Self` type so it behaves
exactly like `self: Self`. However, the exact spelling used must match
between a forward declaration and a definition, following #3763's rules
around declaration matching.
Generated functions, thunks, and C++ interop import/export build `self`
as the first explicit parameter, and the `self`-type override (e.g.
Derived->Base for a virtual override) applies to the explicit `self`.
Placement is validated by new diagnostics: `SelfInImplicitParamList`,
`SelfNotFirstParam`, and `SelfOutsideParamList`. The benchmark source
generator and the documentation adopt the `(self)` shorthand; the
prelude, the examples, and the test data are migrated in the following
commits.
Assisted-by: Claude Code with Claude Opus 4.7
---------
Co-authored-by: josh11b <15258583+josh11b@users.noreply.github.com>
Fix import logic to make all imported packages be children of the
`NameScopeId::Package` scope. Previously, indirectly-imported packages
would end up as children of their importing package's scope, which
resulted in them not being treated as packages at all, and in particular
not being fingerprinted as packages.
Fixing that caused a failure in the fingerprinting logic as we started
to encounter packages with no correspoding import scopes. Instead of
looking for import scopes, use a simpler mechanism to map packages to
their package names, and clean up.
Unfortunately the latter change churns all the fingerprints again :(
Hopefully this is the last time for a while.
When we import from another library in the same package, its entities
end up with our library as their parent scope, resulting in cross-file
fingerprint mismatches. Instead, only include the library ID when
fingerprinting either a package-private entity or an `ImportIRId` that
refers to a particular `SemIR::File`.
Fixes link failures when referencing a symbol involving a fingerprint
from a different package.
Previously we included the `Namespace`'s `import_id` as part of its
fingerprint, which caused local and imported namespaces to get different
fingerprints. We now store the `import_id` on the `NameScope` instead of
on the `Namespace` inst to avoid this problem.
Also, when we reach a package-level `NameScopeId`, consistently
fingerprint it as a (package name, library name) pair. Previously the
fingerprinting depended on whether it was imported or not, as an
imported `NameScopeId` had a parent scope (the current package). We need
to include the library name here so that private entities with the same
name in different libraries have different fingerprints.
When a class extends an interface, referring to a member name of the
interface as an unqualified name should refer to the class's
corresponding associated entity value, not to the associated entity
itself. Similarly, in an `impl`, unqualified names of associated
entities should refer to the `impl`'s corresponding value for that
entity.
To support this, we treat `impl`s as `extend`ing their implemented facet
type, and we make lookups into an extended facet type use the `Self`
type of the extending `impl` or `class` if lookup finds an associated
entity. We already did the latter if the extending entity was an
interface; this extends the existing support for these other cases.
This is only fixing the decision about *whether* to produce a witness.
Implementation of the witness is still a TODO, though where a body is
generated, it should also precisely reflect where one _needs_ to be
generated.
Note the tests:
- toolchain/lower/testdata/function/generic/import_core_witness.carbon
- toolchain/lower/testdata/function/generic/import_unused_def.carbon
These tests can probably be produced _without_ Core.Destroy, but I found
the essence of them while trying to build //examples with Core.Destroy
and a simpler minimization wasn't striking me.
Assisted-by: Google Antigravity with Gemini
---------
Co-authored-by: jonmeow <jperkins@google.com>
This will be used for const-evaling functions. Splitting into a separate
commit since it touches a lot of test files, and a couple fail_todo
tests are no longer failing.
Previously we forced a temporary materialization, resulting in it being
treated as an ephemeral reference expression. This change allows
```carbon
var x: Class = {} as Class;
```
even when `Class` is not copyable.
This is a step toward removing the index from `InitForm`, so that equal
form values always have equal representations.
---------
Co-authored-by: Jon Ross-Perkins <jperkins@google.com>
This is iterating on how `Destroy.Op` generates, to start adding body
capabilities. This changes the way the signature is created, and adds a
`CoreWitness` function kind so that mangling can prevent name
collisions. The result is that what _was_ `DestroyOp` is now
`Core.Destroy.Op` or, as can be seen in
toolchain/lower/testdata/interop/cpp/nullptr.carbon,
`_COp.<hash>:core.Destroy.Core` where `:core` is indicating that it's a
core witness (taking a note from `:thunk`).
Assisted-by: Google Antigravity with Gemini 3 Flash
Implementation of unused pattern bindings #2022, continued.
Whereas previous PR #6460 took care of parsing, and PR #6479 prepared
the stage by using _ in some test cases, this PR has the the actual
implementation, using a simple dataflow analysis.
---------
Co-authored-by: Burak Emir <bqe@google.com>
Co-authored-by: jonmeow <jperkins@google.com>
Currently each interface has a `Self` facet internally that becomes a
binding to every entity inside the interface: associated constants,
functions, and require decls. Each of these has to be independently
generic as a result. This makes is challenging in extended name lookup
to move into an extended scope of an interface, as we have a specific
for the interface, but the names within require a different specific
that includes a `Self` facet value.
We generalize this relationship by adding a second generic to Interface,
called `generic_with_self`. When we want to work with entities inside
the interface, we move from the interface-without-specific to the
interface-with-self specific by adding a Self to the specific. This is
done independently of any particular entity inside the Interface, as
those entities are now all members of the interface-with-self generic.
Associated constants no longer need a generic of their own, as they do
not have separate generic bindings. Functions retain a generic, but if
the function has no generic arguments, it will have no bindings of its
own now.
Require decls retain a generic so that their specific can be
instantiated separately from the interface. Requiring the interface to
be complete does not require the types in a require decl to be complete
unless it is modified by `extend`. So we allow them to be completed
later by keeping them in a separate generic.
Named constraints look like interfaces and gain the additional inner
generic-with-self, with the same relationship to require decls.
This removes the need for name lookup to perform Substitution of a Self
facet into the extended scope instruction. Instead, the
`SpecificConstant` instruction inserted by a `require` decl is part of
the interface-with-self generic. When looking through a FacetType for
extended scopes, for each interface, we push the scope with the specific
for the interface-with-self. Then the constant value of the
`SpecificConstant` is correctly modified by the provided self
automatically through applying that specific.
The key changes are:
- Function output parameters are now prefixed with `out`, and more
consistently formatted as named parameters.
- Function and inst output arguments are now written as part of the inst
form, rather than as one of the inst arguments.
As a drive-by fix, this also changes `Temporary::storage_id` from
`DestInstId` to `InstId`, because it doesn't represent an output
parameter of the `Temporary` inst itself.
See the review of
[#6532](https://github.com/carbon-language/carbon-lang/pull/6532) and
[this Discord
discussion](https://discord.com/channels/655572317891461132/999638000126394370/1458268977020141589)
for additional background.
Pursuant to recent decisions on #6124, switch `Destroy` to use a
`CustomWitness` for its implementation. Right now this is manufacturing
no-op implementation functions on each lookup, which obviously isn't
ideal but is intended as a first pass. I'm mostly trying to find the
right balance between updating the approach to reflect new decisions,
while still breaking apart work in a way.
The `CoreInterface` logic is intended to build on `CoreIdentifier`
support. We have a number of additional interfaces that require
specialized logic, and that'll extend pretty far with C++ interop, so it
seemed easiest to have a generic function for it. That's what's
replacing the logic inside C++ interop that was doing string comparisons
(which could have already been moved to `CoreIdentifier`, I just missed
it in my first pass).
This adds `CustomWitness` support because the `Destroy` witnesses can be
imported cross-file. `CustomWitness` was previously only used for C++
types, which don't yet support import, which is why that wasn't
previously an issue. The addition of `query_specific_interface_id` is
similarly needed in order to get correct sorting of witness blocks when
imported.
This PR also removes builtin constraint logic (note this is in a
separate commit to help review; it's not a separate PR because it's
difficult to split apart without tests breaking). This had been made
generic with the expectation that destroy, copy, move, and conversions
would all need related support. Under the new decision, we are not going
to do blanket impls and will instead just manufacture a `CustomWitness`
for everything.
A lot of SemIR fingerprints change, but that's probably because the
addition of `Destroy` on core classes is yielding structural changes.
The impl's body block has to end before we make its ImplDecl
instruction, and the witness instructions come later, so they don't end
up in the body block. Currently they just end up in the enclosing (file,
typically, or class) scope block.
Add a new InstBlockId to Impl for holding witness instructions, and
explicitly insert them into that block. Then include those instructions
into the scope of the Impl for naming, and format them into the Impl
right after the body block.
This is based on #6484
Instead of naming the root namespace `package` (because it's accessed by
the `package` keyword), change it to use the current package name. Note,
buried in the checksum changes,
`toolchain/check/testdata/package_expr/fail_not_found.carbon`:
```
- // CHECK:STDERR: fail_not_found.carbon:[[@LINE+4]]:16: error: member name `x` not found in `package` [MemberNameNotFoundInInstScope]
+ // CHECK:STDERR: fail_not_found.carbon:[[@LINE+4]]:16: error: member name `x` not found in `Main` [MemberNameNotFoundInInstScope]
```
for:
```
// CHECK:STDERR: var y: i32 = package.x;
// CHECK:STDERR: ^~~~~~~~~
```
I'll leave it to you if you prefer this; the alternative I see is to
just rename `IsCorePackage` to `IsImportedCorePackage`, and/or change it
to a helper that takes a `Context` and does the right thing with
`parse_tree` (which, I need for `Destroy`-related reasons and was my
default approach).
This is a prerequisite for support for interop with C++ template names.
No behavior change here, except that it sadly changes the fingerprinting
for a lot of tests.
Give TupleLiteral and StructLiteral a constant value, if their contents
have constant values. Their constant values are TupleValue and
StructValue respectively. This supports their ability to convert to a
constant type (or facet type).
This way when deduce finds a TupleLiteral as the argument to a
_symbolic_ facet type, it can also find a constant value to use for that
argument. This allows deduction to move onto step two, where it can
substitute into the symbolic parameter from previous deduced arguments,
and then perform the conversion from the TupleValue to the desired facet
type.
Allow `PerformBuiltinConversion()` to convert from a canonical
TupleValue or StructValue to `type` instead of only from literals. Then,
also support conversion from a symbolic binding of type TupleType or
StructType to `type`.
They are not used for impl lookup or verifying anything yet, but now
they appear in the textual semir.
---------
Co-authored-by: Jon Ross-Perkins <jperkins@google.com>
This resolves a TODO in `expr_info.cpp` by using the inst kind rather
than the bound value to track the binding's category.
Since we're churning all the `bind_name` insts in testdata anyway, I'm
also taking this opportunity to align the inst naming with the design's
terminology, by calling these insts "bindings" (this aspect of the PR is
dependent on #6231 resolving an ambiguity in that terminology). For
consistency we'll need to rename several other insts as well (see the
TODO on `RefBinding`); I'm deferring that to a separate PR to minimize
the review load, but I think those name changes are in-scope for this
review.
When deducing arguments for generic parameters of an `impl`, the
deduction calls `Convert` on the input arguments. Often, the input
argument is a facet, and needs to be converted to a type via
FacetAccessType in order to produce a different facet. These
instructions end up being added to the semir, but only their constant
values are needed for the resulting specific returned from Deduce.
In the best case, these extra instructions are just noise in the semir,
or they just cause instruction names to get differentiated with larger
suffixes.
In the worst case, these extra instructions contain references to
instructions from a generic context, and leak them out of that generic
context and into another. In particular, when importing a
LookupImplWitness instruction, the re-evaluation of it can do deduce
(when the lookup is against a generic `impl`). The instructions created
in Deduce are not part of the import, and end up referring to imported
instructions from the local context, which leads to confusion in the
toolchain, and can crash.
The `import_self_specific.carbon` test demonstrates this. It causes the
`I.F` function to be imported from the `I` interface when building the
witness table for the `impl`. Doing so imports the specific of `C` which
includes a LookupImplWitness for `Self.Accoc` in `I`. The `Self` is a
BindSymbolicName with generic binding index 0, in `I`. When Convert
creates instructions in the generic `impl forall D`, however, they end
up referencing and including this BindSymbolicName into its eval block.
But the generic binding 0 in the `impl` is a very different thing (a
value of type `E`). This confusion leads to crashes.
The SymbolicBindingType refers to the type value that will be
substituted in for the BindSymbolicName, but holds onto the EntityNameId
from the BindSymbolicName instead of (or in addition to, for now) the
instruction.
The EntityNameId will be used to look in the ScopeStack to find the
witnesses either from the BindSymbolicName instruction, or other
instructions that specify `impls` constraints against the EntityName.
This will allow us to have the `T` in `I(T)` resolve to a `.Self`
reference in the type so that we get type equality with the binding's
type: `T:! I(.Self)`.
This also does a little restructuring in the same direction, following
#6124.
Leads want `Destroy` to work similarly now for all types. As a
consequence, there doesn't seem to be as much benefit to splitting off
aggregate destruction. In this PR, the `type.destroy` function can now
be expected to destroy anything that's destructible; that means it'll be
usable for the `final fn` once that support is available.
Similarly, this gets rid of the impls other than the single blanket
impl, now using `type.can_destroy`. Since they all need to use the same
function, there's no benefit to splitting approaches. Also, now it can
just be a `final impl` since there should be no need for people to
create specializations -- if this blanket impl applies, it means the
`final fn` is the same.
This also slips in `partial` support since there's no reason to have it
diverge anymore. Also `abstract`, which I'm not sure is broadly testable
since most cases it'd come up, the `abstract` keyword is explicitly
detected/rejected.
Note though that this doesn't make any really big changes. It's just
realigning on the leads decision. I'm going this way to try to reduce
name-related churn for other changes.
This makes convert more consistent, it always makes a FacetAccessType
for a facet value, rather than only doing so after lookup returns. The
intention for this is that FacetAccessType will evaluate to
SymbolicBindingType in the future, so this will expose that constant
value to impl lookup instead of the original facet value, which will
avoid impl lookup having to deal with `.Self` or `BindSymbolicName`
specifically.
Right now, the class destroy impl is incorrectly generated (first
discussed [in
Discord](https://discord.com/channels/655572317891461132/941071822756143115/1418614787449032826)).
If we want it to be correct, deferred definition logic would need to be
added, and the declaration would need to be moved inside the `class`
scope (along with whatever generic logic that needs).
This instead switches to a blanket impl, to avoid creating latent bugs
with generating the `impl` and function body in the wrong scope. This
approach uses the same blanket impl as aggregate destruction that was
added by #6098.
The intent here is to allow progress on other parts of `Destroy`. For
example, under this model the implementation of the function body could
be done as part of lowering the specific.
This is in support of a goal of changing the blanket `destroy` impl to
use (roughly):
```
private fn CanAggregateDestroy() -> type = "type.can_aggregate_destroy";
// Handles aggregate type destruction.
impl forall [AggregateDestroyT:! CanAggregateDestroy()] AggregateDestroyT as Destroy {
fn Op[addr self: Self*]() = "type.aggregate_destroy";
}
```
That isn't done here because there's still other issues that migrating
raises. What this *does* do is add the builtin functions, and in
particular, support to `FacetTypeInfo` to make `CanAggregateDestroy`
work.
The "special requirement" approach in `FacetTypeInfo` allows us to
support restricting a blanket impl under the current approach of impls.
Maybe we'll find a cleaner approach that can work in the future, but
this fits into the current model by propagating similar to other
requirements. I'm using an enum mask because we have a number of similar
things to add (e.g. copy, move) but I'm not sure we need a full vector.
A few alternatives considered were:
- Supporting syntax more like `where .Self impls
TypeCanAggregateDestroy(.Self, SupportedInterface,
UnsupportedInterface)`. I think it'd be a little cleaner, but requires
better compile-time evaluation in order to assess the type of the call.
Right now it's expected to be a `FacetType` too early to make this work,
and I was concerned about pouring too much more time down this route.
- Providing an actual interface, in particular doing name lookup back
into `Core.` for an interface. This would've added name lookup overhead,
and the question of whether an `impl` exists.
- Generating an interface. This avoids the name lookup, but would still
raise the question of whether an `impl` should also be generated. Work
I've previously done generating interfaces for class destruction also
feels complex to both write and understand (an unfortunate issue).
- Still modeling as an `ImplsConstraint`, for example by defining a
special `InterfaceId::CanAggregateDestroy = -2` similar to what we do on
other ids. I was hesitant because of how this expands the number of
modes of `InterfaceId`, and things for consuming code to watch out for,
for what feels like a relatively niche set of use-cases that are only
interface-like.
---------
Co-authored-by: Dana Jansens <danakj@orodu.net>
This uses each vector's size as a barrier between lists, to eliminate
the possibility of incidental collisions between entries of different
lists. This is the same as is done inside `AddBlock`.
Attach the cleanup to the `Temporary` instruction instead of to the
`TemporaryStorage` instruction. We create `TemporaryStorage`
instructions speculatively when creating an initializing expression, and
may overwrite those instructions with other instructions if it turns out
that a temporary is not required. Instead, wait until we finalize the
temporary and create a `Temporary` instruction to register the cleanup.
The self access is important; for the test `generic_class.carbon` being
added to `toolchain/check/testdata/class/destroy_calls.carbon`, it was
using `%T.as.Destroy` instead of `%D.as.Destroy`, indicating the default
blank impl was being used instead of the type-specific version. That
test is trying to focus on the issue, but the delta is visible in a
couple other files in this PR, for example
`toolchain/check/testdata/class/generic/init.carbon`.
I'm separately working on getting rid of the default impl, which is how
I noticed this.
I was thinking about this for destruction, which I may not be able to
use it for, but still think this may be a good change to keep features
consistent.
Although this focused on `Destroy` support, some choices here around
`implicit_type_impls` are because copy/move will likely follow a similar
approach. I'm trying not to predict too much about how we'll structure
those, but I'm putting `Destroy` impl logic in a file that could perhaps
be shared with those. They'd likely be interested in similar things,
e.g. traversing members of types (particularly class, struct literal,
tuple literal).
At present this sets the destroy function as `no_op` which is consistent
with current logic, but has a TODO to correctly define.
Constant importing for functions changes slightly due to some issues I
was having with `GetFunctionType`. zygoloid suggested this approach to
avoid `EvalInst` logic.
Adds a flag for controlling whether to generating these impls. While
this does generation for `class`, as noted above this'll also need to be
done for tuples and struct literals, which would leave the `none.carbon`
min_prelude unable to use any types. Note if destruction *would* occur,
it'll still look up `Core.Destroy` for that and fail, but that's already
true of any test using `none.carbon`. I'm trying to use the flag to see
if we can keep `none.carbon` working mostly-consistently.
I'd tried separating out the flag to #5852, but that got a lot of
pushback over whether the behavior was appropriate. I'm hoping that the
interactions here make it clearer why the particular approach -- the
goal is not to enable advanced testing, or create some new end-user
behavior that we really support, it's just to keep no-prelude tests
functional. The main question raised there was why not just keep
generating `impl T as Core.Destroy` if `fn destroy` is present -- but I
think here it should be apparent that would require additional
complexity, as the generation of `impl T as Core.Destroy` is not
currently conditioned based on the implementation of `fn destroy`. I'd
rather add complexity to this flag only if it's enabling interesting
test functionality.
---------
Co-authored-by: Geoff Romer <gromer@google.com>
Change impls from `<interface>.impl` to `<self>.as.<interface>.impl`,
and *member* functions to `<parent scope>.<fn>` (non-member functions
exclude their parent scope). Stop special-casing builtin functions,
given the new naming scheme.
The purpose of this is to make it clearer when a member function is
being accessed and, if so, which member function. In particular, we
often access interface `Op` functions. The builtin function
special-casing was intended to help with that, but we still have lots of
`Op` functions. This particular approach should make the interactions
clearer.
This changes up queueing of block IDs a little because, in particular,
we need to process bodies of entities only after constants finish
processing. But, it should also result in less memory usage during
processing because it means we have less on the insts stack at any given
time, since we track a block rather than all instructions contained by
the block.
This switches from the `CollectNamesInBlock` approach for entities, to
instead traversing entities as they're encountered. For example, when
traversing constants, when a type is found, the entity will have its
block queued for processing.
This leads to a change in the traversal order, which affects
disambiguation done by numeric sequencing (since that's just showing the
traversal order).
This will allow for simpler "name based on name" logic. This is
something I plan to use for:
- impls: `<type>.as.<interface>.impl`
- functions: `<entity>.<member function>`
- Note an impl may be used as the entity for a bound function.
By naming the entities as they're encountered, I'll be able to rely on
the generated names rather than recalculating them.
To assist this, I'm also differentiating between the ambiguous and
disambiguated name. Otherwise, we could end up with things like
`<function>.<disambiguator>.<call>.<other disambiguator>`, where the
repeated disambiguator may not be necessary in order to get full
disambiguation. It's also a smaller delta from the current output.
Note, changing `Name` to a class felt appropriate given its shape. I was
also noticing that parts of its API were unused, and the class helps
detect unused private members.
---------
Co-authored-by: Geoff Romer <gromer@google.com>
Dana Jansens
Geoff Romer
Christopher Di BellaandRichard Smith
Özgür T. ÖnsoyandDana Jansens
Chandler Carruthandjosh11b
Jon Ross-Perkinsandjonmeow
Nicholas Bishop
