C++ pointers to Carbon methods are supported using the same mechanisms
as for Carbon functions: we export the method to C++ and then form a
pointer to the exported method. This change does not support invoking a
C++ method pointer from Carbon, which will be more complicated because
we need to model instance binding on the Carbon side.
Check that every use of a non-constant instruction is dominated by a
definition of that instruction. Remove the fake (instruction creation
order based) dominance checks in convert; these start spuriously failing
during template instantiation of initializers.
Assisted-by: Claude Opus 5 via Antigravity
Add support for deferring initialization as a template action, and
performing the deferred initialization during template instantiation.
This is substantially more complex than other conversion actions, for
two primary reasons:
* The initializer in the generic may have storage arguments as inputs.
We model an initializing expression as having a "slot" where
initialization writes the location that should be initialized by that
initializing expression, and that needs to be an output of the
initialization action.
* Initialization from a tuple or struct literal needs to recurse into
that literal, and the literal will have been spelled in the generic,
meaning we don't have an `InstId` that can be used to name the specific
version of the initializer as input for nested conversions.
These issues are addressed by introducing two new features to the action
machinery:
In addition to `InstAction`, we now have `MultiInstAction`, which is an
action that produces a tuple of instruction values instead of a single
instruction value. Initialization actions produce one instruction for
the final result, which is spliced at the point of initialization, plus
one instruction for each storage argument, which are spliced into the
storage argument slots in the original generic. During initialization,
if we find one of those splices in the storage argument of an
initializing expression, we return the new storage argument back to the
initialization action to be included in the specific, instead of
overwriting the storage argument in the generic.
Actions whose `PerforrmAction` takes a `SpecificId` as input no longer
perform automatic refinement of their operands to specific instructions.
Instead, the action is given control over when and where it performs
that refinement. In `InitializeAction`, we use this freedom to form a
`SpecificInst` for the initializer in the primary output block, and form
a `SpecificInst` for the target in the target block. When detecting
whether we are initializing from a tuple or struct literal, we step over
the `SpecificInst` and track its `SpecificId`, and if necessary create a
new `SpecificInst` wrapping the sub-initializer when we recurse into the
nested element conversion.
Assisted-by: Claude and Gemini via Antigravity
The type `type` is now a `FacetType` inst with no constraints. This
brings the model implemented in the toolchain into better alignment with
the language design. The `SemIR::TypeType` struct remains as a scope for
holding the `TypeInstId`, `ConstantId`, and `TypeId` constants, but is
not an `InstKind` anymore.
The `TypeType` inst looks a lot like singletons, but there are many
`FacetType` insts so it doesn't quite fit that model. So we put it
alongside singletons with a fixed inst id but refer to it as a more
general "builtin" inst that is not a singleton.
`Namespace::PackageInstId` is similar, and we group it with `TypeType`
conceptually as another builtin instruction with a fixed id.
No conversion is needed anymore to use a `type` as a facet, since types
also have a `FacetType` type. This simplifies and removes a number of
helpers and branches throughout the code.
The `TypeType` inst is now part of the constant store, so we end up
printing it in the constants block in every test. But it's also named
`type` rather than `%type` to preserve the majority of existing
formatting behaviour, though this does look different from other
constants.
Assisted-by: Opus 5 was used to generate a first draft and validate the
refactoring. Though nearly everything non-trivial the tool wrote has
been modified or rewritten.
We use the same conversion codepath to handle both qualification
conversions and derived-to-base conversions, because we allow both to be
performed at once. However, we were previously modeling the
qualification conversion as happening *first*, and producing a result
whose type is the target type of the overall conversion (that is, the
base class type). That led to bogus SemIR, where a `Derived` -> `const
Base` conversion would first have a "compatible" conversion from
`Derived` to `const Base`, *then* an access of the base subobject (of
type `const Base`, within an object of type `const Base`).
We now reverse the order: first we do a derived-to-base conversion,
which already has logic to preserve qualifiers, and then we do any
necessary qualification conversions on the result to reach the overall
target type.
In passing, we now skip forming the `as_compatible` instruction at all
for a pure derived-to-base conversion that has no qualification
conversion, simplifying the SemIR by one instruction in the common case.
### Description
When looking up default initializers for class elements in
`ConvertStructToClass`, the compiler previously assumed that every
member looked up from the class scope was a `FieldDecl` and called
`GetAs<SemIR::FieldDecl>` directly.
For a derived class with a base class, looking up `base` returns a
`BaseDecl`, which caused a `CHECK` assertion failure when casting to
`FieldDecl`. Use `TryGetAs<SemIR::FieldDecl>` instead so non-`FieldDecl`
entries like `BaseDecl` are recognized as having no default initializer,
cleanly diagnosing that the `base` field is missing.
Fixes#7722
Assisted-by: Google Deepmind Antigravity
Test passing a template argument or a symbolic argument to a template.
Fix a bug in the template case where we'd crash when instantiating a
dependent discarded expression, because conversion produced an
`InstId::None` which the actions machinery did not expect and crashed
on.
Generalize ConvertToValue template action to handle other kinds of
conversion target that don't perform initialization. Initializing
conversions will need more work since they also need to use a splice to
form the storage block.
This allows various templated constructs to get further through
checking, but typically we hit another unsupported action such as a
conversion or call, so it's not enough to make much work.
In Convert, we require the source value's type to be compete so that we
can look for `base` classes and `adapt` relationships. However these can
only be present in a `ClassType`, so we only need `ClassType`s to be
complete.
Reduce the requirement in Convert to not complete types that are not a
`ClassType`, and which can not contain a `ClassType` as part of their
class.
Ideally we would only _only_ require the `ClassType` itself to be
complete, and only if we're looking for a base or adapt. However lower
depends on us completing all Convert source types that contain a class.
This seems to suggest we're lacking checks for complete types somewhere
else and Convert is making up for it. A TODO has been added. The
`toolchain/driver/testdata/compile/optimize/optimize_debug.carbon` test
is an example that CHECKs due to failing to verify the LLVM module if we
do not compute the complete type of all class-containing types in
Convert.
The critical step this PR is doing is to stop trying to complete a
`FacetType` when converting from a facet. This avoids trying to complete
a named constraint when converting `Self` inside that named constraint.
Doing so causes a cycle when the conversion of `Self` is performed in
eval of an `extend require` decl, since requiring the named constraint
to be complete re-evaluates the `extend require` decl again. A test is
added that crashed in an infinite loop before this change.
It also depends on #7584, which was intended to be an optimization but
is now load bearing. Because converting `Self` leaves an impl lookup
inst behind, and if that inst is re-evaluated inside impl lookup (by
forming a specific of a `require` decl through identify) then we have a
similar cycle.
Implement the toolchain side of proposal #7254, removing the `:!`
binding
syntax for generic and template parameters in favor of the keywords
`generic`,
`template`, and `runtime` plus contextual defaults for phase.
For valid programs this is semantics-preserving: each binding resolves
to the
same phase, and produces the same SemIR, as it did under `:!`/`:`. The
parser
derives a binding's phase from its syntactic context plus any explicit
phase
keyword; new diagnostics and error recovery for misused keywords are
described
below.
Implementation details for each component:
- Lexer: remove the `:!` (`ColonExclaim`) token, move its virtual
parse-node
budget onto `:`, and add the `generic` and `runtime` keywords.
- Parser: thread a `BindingContext` (`ExplicitParam`, `DeducedParam`, or
`CompileTimeEntityParam`) from declaration introducers down through
parameter
lists to each binding pattern, using a one-token lookahead to
distinguish a
name-qualifier parameter list from a declaration's own final list.
Parameters
of a compile-time entity (`class`, `interface`, `constraint`, `choice`,
`alias`, `export`, `namespace`) and deduced `[]` parameters default to
checked
generic; explicit function parameters and local bindings default to
runtime.
`HandleBindingPattern` resolves the phase from that context plus the
keyword: a
`generic` keyword needs no node of its own (the phase is carried by the
binding's node kind), while a `runtime` keyword is preserved as a
`RuntimeBindingName` node so `check` can name it in a diagnostic. A
phase
keyword that is merely redundant with the contextual default is
diagnosed
here, without invalidating the parse tree.
- Check: a phase keyword that is invalid for its context (for example
`runtime`
on a checked-generic parameter) is diagnosed here, and recovers by
building an
error binding that still introduces the name so that later uses of it do
not
produce cascading errors.
The removed `:!` syntax is now rejected as an ordinary parse error.
The `form`/`:?`/`->?` ("extended types") portion of proposal #7254 is
left for a
separate change.
Assisted-by: Claude Code
This proposal removes the `:!` syntax for generics and templates in
favor of keywords (`generic`, `template`, `runtime`) and contextual
defaults for phase. It also replaces `:?` with `fwd` and introduces
`exttype` for extended types.
Assisted-by: Antigravity with Gemini, and Claude
---------
Co-authored-by: Geoff Romer <gromer@google.com>
Move the existing derived->base conversion earlier in
`PerformBuiltinConversion`, into the block that handles qualifier
conversions. This allows, for example, converting from `partial Derived`
to `partial Base` -- see the tests in
`toolchain/check/testdata/class/inheritance/derived_to_base.carbon`.
Notably this allows accessing fields in an abstract base class via a
derived class without going through `base`. E.g.
`my_obj.field_in_base_class` rather than
`my_obj.base.field_in_base_class`.
In `Convert`, allow forming a value or reference of abstract class type,
but not an initializer.
For now, limit the scope to just `ClassElementAccess` to avoid affecting
tests where I'm unclear if allowing abstract types is correct.
The conversion will just produce an ErrorInst output.
Right now I am not sure how to get an ErrorInst into that position, but
with https://github.com/carbon-language/carbon-lang/pull/7364 rejecting
`.Self` we end up with this, and it crashes otherwise.
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>
This is only valid when the operand is an initializing expression that
holds a copy of the value, but we were incorrectly also forming it when
the operand was an in-place initializing expression.
Fixes a crash in lowering when attempting to lower an invalid
`value_of_initializer`.
This helps us move away from the clone-with-modifications approach to
thunking, which gets unwieldy as signatures get more complex.
---------
Co-authored-by: Richard Smith <richard@metafoo.co.uk>
As suggested in [1], replace `FieldInitializerMap` with a `FieldStore`.
The corresponding `FieldId` is now stored in `FieldDecl`. To make room
for the `FieldId`, the `ElementIndex` is now stored in the `Field`,
along with the initializer.
In import_ref.cpp, resolving `FieldDecl` initializers is now supported,
and in convert.cpp `LoadImportRef` is called to do so. The
`field_initializer_import.carbon` test now passes.
Printing a `FieldDecl` instruction now prints the initializer as well,
if present. See field_initializer.carbon for an example.
[1]:
https://github.com/carbon-language/carbon-lang/pull/7238#discussion_r3283217158
Allow a `ref`-tagged expression to be converted to match a reference
parameter. Move the `ref` checks to the start of `Convert`. Remove the
diagnostic for applying `ref` to a non-reference expression so that
non-reference expressions that convert to a reference would be accepted
(although we don't currently have any such conversions).
Assisted-by: Gemini via Antigravity
In handle_let_and_var.cpp, field initializers are now handled like
regular `var` initializers, by calling `LocalPatternMatch`.
In pattern_match.cpp, `FieldDecl`s with initializers are handled by
storing a value in `SemIR::File::field_initializers()`. This is a new
map where the keys are `FieldDecl` `InstId`s and the map values are
`InstId`s representing the initializer value.
In convert.cpp, `ConvertStructToStructOrClass` now has a `get_default`
function parameter that callers can use to provide a field default.
`ConvertStructToClass` uses this to provide a default from field
initializers.
This enables thunking to work when the function has `ref` parameters,
without jumping through hoops to add `ref` tags in the desugared
function body.
This also renames `is_operator_syntax` to `is_desugared`, which is more
general and more accurate.
See
[here](https://docs.google.com/document/d/1rWcueFwIfZox6GKVGxiUG4cBzjrZ6djXiIDGyJDtrE4/edit?tab=t.0)
for the design doc.
This also removes the default value of the `result_type_inst_id`
parameter of `HandleAction`, moves it before the action in the parameter
list, and documents it. This solves two problems:
- The default made it easy to forget, leading to unnecessary
`TypeOfInst` instructions.
- When it was present, putting it after the fairly "bulky" action
argument tended to make the callsite harder to read.
When an initializing expression is used to initialize a var parameter,
we need to create the storage earlier in SemIR than the initializing
expression. To do so, pass a pending block to initialization containing
the var storage.
Also stop using `temporary` for this purpose, since we treat temporaries
as potentially-constant and immutable, but `var` parameters can be
mutated by the callee. We should ideally introduce a new kind of
instruction for this purpose but for now we just use `var_storage`.
- A function with a return declaration always has exactly one
`ReturnSlotPattern`, representing the whole return declaration (whereas
previously that was omitted for value and reference returns).
- The `ReturnSlotPattern` always has a subpattern with the same form.
`OutParamPattern` already plays that role for initializing forms, and
`TuplePattern` will play that role for tuple forms. This change
introduces `ValueReturnPattern` and `RefReturnPattern` to represent
value and reference return forms.
- As before, the `ReturnSlotPattern` has a corresponding `ReturnSlot`
that represents the output that is initialized by a `return` statement.
Its structure parallels the structure of the `ReturnSlotPattern`, so we
need `ValueReturn` and `RefReturn` insts that correspond to
`ValueReturnPattern` and `RefReturnPattern`.
This is a step toward supporting generic return forms, where the
`ReturnSlotPattern`'s subpattern may be an action: this change ensures
that evaluating the action for a specific form produces the same SemIR
as if the form were concrete to begin with. More speculatively, this
should simplify the implementation of `return` statements with compound
return forms.
---------
Co-authored-by: Chandler Carruth <chandlerc@gmail.com>
- Rename `ActionIsDependent` to `ActionIsPerformable` (with negated
meaning), because that name is more concrete and, um, actionable.
- Replace `OperandIsDependent` with `OperandDependence`, which returns a
`ConstantDependence` instead of a bool. We need this additional
generality for handling form actions, where we sometimes need to ask
whether something has _any_ dependence, not just whether it has template
dependence.
Instead of allowing lower to pick whatever type layout it desires,
compute the layouts of types as part of completing the type, and make
lower build types that match that representation.
For now we assume that all pointers are 64-bit, since we don't have
access to target information. We allow tail padding reuse for structs
and tuple types (and by extension, for classes, since they use structs
as their object representation), but not for arrays.
In order to build matching LLVM types, we create LLVM packed structs
where necessary, and we insert inter-field padding on the end of the
previous field so that GEP indexes still always match Carbon's
ElementIndexes.
We don't yet use the computed alignment much in LLVM IR generation -- in
particular, `alloca`s, `load`s, and `store`s should probably use the
computed type alignment, but don't.
Assisted-by: Gemini via Antigravity
Fix some situations where we'd drop the storage argument when building
an in-place initializing expression. We now guarantee that an expression
with the in-place initializing category always has a storage argument.
Instead of recursing back into Convert, make CppThunkRef conversion just
add an extra step to category conversion, performing a copy conversion
followed by an ephemeral reference binding conversion.
Remove special-case handling in conversion logic for C++ enum types,
synthesize a custom witness of `Core.Copy` using the `primitive_copy`
builtin function.
Add `InstIs`, `GetInstAs`, and `TryGetInstAs` which act on the
underlying constant instruction in a constant value, to save an explicit
call to `GetInstId`.
```carbon
context.insts().GetAs<InstT>(context.constant_values().GetInstId(const_id))
```
can now be written as simply
```carbon
context.constant_values().GetInstAs<InstT>(const_id)
```
For future work, we might provide `GetInst()` so that
`context.insts().Get(context.constant_values().GetInstId(const_id)` can
be shortened also.
Performing a lookup against `Self` inside the definition of the named
constraint leads to cycles, as described in the document [Self
contradictions in Named
Constraints](https://docs.google.com/document/d/17rn2XmME8o2MM4OJqatSVuMa1iYZ1PAgcNrf0PXR9Q4/edit?tab=t.0).
To prevent those cycles, this change introduces a large refactoring of
impl lookup.
The impl lookup done inside eval is reduced to only performing
monomorphization. That is it:
- Only looks for an provides final witnesses.
- Is not allowed to identify the facet type of the query self.
- Returns either a final witness or None (or an error)
The paths for finding non-final witnesses are now done outside of eval,
directly in the initial `LookupImplWitness()` function. If no final
witness it found through eval, the resulting non-final
`LookupImplWitness` instruction witness is returned. It does not produce
cycles to identify the facet type of query self outside of eval, since
that does not result in repeating the identification when resolving
specifics of the named constraint or require decl.
Move the ArrayStack for Context::require_impls_stack into a new class
which tracks a NamedConstraintId (or InterfaceId) for each frame of
RequireImplsIds, so that in type completion we always can find the
correct frame for a given named constraint which is still being defined,
in order to find the RequireImplsIds in the in-progress definition.
This follows up on a discussion about wanting to use `Any*` inst
clusters to handle boilerplate construction, with the issue that
`UncheckedLoc` use removes validation. Some context is at
https://github.com/carbon-language/carbon-lang/pull/6930#discussion_r2963157428.
This folds in `MakeImportedLocIdAndInst` because the logic is related,
particularly for `LocId` values which are `ImportIRInstId`, and it
eliminates questions of what the right function is to use.
This uncovers an error in the `NodeKind` associated with
`FormBindingPattern`. For now I'm just adding a TODO regarding that.
Assisted-by: Google Antigravity with Gemini
This resolves some todos, and makes `Convert` safer to call, which
unblocks some changes in pattern matching that I'm working on.
Assisted-by: Gemini 3.1 Pro via Antigravity
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.
Treat the initial sequence ofarguments in a call to a C++ function up to
and including the last argument that is a type or template as being the
explicit template arguments for the call, rather than rejecting them
because they can't be converted to the parameter types.
Implements the current direction on leads issue #6768, except that no
syntax for explicitly annotating an argument as being a template
argument is provided.
---------
Co-authored-by: Carbon Infra Bot <carbon-external-infra@google.com>
When initializing `.base` in class initialization, use `partial Base` as
the destination type rather than `Base`. Treat `partial Base` as not
being abstract even when `Base` is.
Allow conversion from a `partial T` initializer to a `T` initializer.
Store the vptr while performing the conversion. Do not store the vptr
when performing a `partial T` initialization, only when performing a
non-partial `T` initialization.
Stop using "performed builtin conversion" as a proxy for whether we
created an initializing expression with a correctly-set storage
argument. That isn't correct in the case where the builtin conversion
creates a new initializing expression without setting its storage, such
as by creating an `AsCompatible` wrapper around an existing initializing
expression.
Instead look at whether the storage argument is a `TemporaryStorage`,
and only overwrite in that case, otherwise assuming that the storage
argument has been set correctly.
This fixes a miscompile that was already visible in our lowering tests!
Introduces `Context` and `SoftContext` messages, which can be introduced
through a `ContextBuilder`:
- The `Context` messages come before the diagnostic in the output.
- The first `Context` message steals the diagnostic level from the main
diagnostic, and turns the main diagnostic into a Note attached to the
context.
- A `SoftContext` message works similarly, but if it's preceeded by a
`Context` or `SoftContext` message, then it is dropped. This can be used
as a default/backup scope when nothing more interesting is provided up
the stack, such as in `TryEvalBlockForSpecific`.
The `ContextBuilder` is provided to a callback through
`Diagnostics::ContextScope`, an RAII type `AnnotationScope` but for
context messages.
This allows a high level operation to provide a context message like
"failed to identify facet type {0}" which will then be used as the error
if a diagnostic is produced during identification, with the latter
diagnostic attached as a note to explain why the contextual operation
failed.
In particular, this allows monomorphization errors (such as an array
bound being negative) to be attached to a higher lever operation instead
of being top-level diagnostics themselves, with the monomorphization
site being a note. This inverts the source code locations that appear in
the diagnostic, so that the top-level diagnostic points to the "user
code" which causes the monomorphization.
This is presented as an alternative strategy to #6753, which plumbed
diagnoser callbacks around to achieve the same goals.
We replace the diagnoser callbacks in type completion and operators with
ContextScope callbacks instead, which now provide better diagnostics for
monomorphization errors. Other callers to MakeSpecific do not yet have
ContextScopes introduced in order to turn monomorphization errors into
more interesting diagnostics.
Geoff Romer
Richard Smith
Lucile Rose Nihlen
Dana Jansens
Chandler Carruth
ATHARVA
Nicholas Bishop
David Blaikie
Jon Ross-Perkins
