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>
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.
- 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>
For calling non-`()` functions, the Carbon->Carbon thunk now takes an
extra reference parameter and writes the target function's return value
out to that parameter. (At the SemIR level this is how returns already
work, but adding this extra reference parameter is needed so that the
function is lowered correctly.) The C++ thunk now creates a local
variable to be initialized by the Carbon thunk, and then returns that
value to the original C++ caller.
This makes the thunk-call logic more general and more supportable by
reusing the existing pattern-matching logic.
---------
Co-authored-by: Richard Smith <richard@metafoo.co.uk>
`ReturnTypeInfo` is built around the assumption that a function call
results in exactly one initializing expression, but with `ref` returns
there may be zero, and in the future composite return forms will enable
there to be more than one. This change removes some usages of
`ReturnTypeInfo`, and restructures the calling code to be prepared for
multiple initializing returns.
This separates the return type from the return pattern, and replaces the
return pattern with a block of return patterns. This is a step toward
support for `ref` returns (where there's no corresponding return
pattern) and compund-form returns (where there may be multiple return
patterns).
This is a followup from #4834, I searched for "invalid" uses in our
codebase. This is mostly changing comments, and a couple debug
functions, but shouldn't affect testable behavior.
Note a couple things I'll highlight as not changing (but could) are:
- `ReturnTypeInfo::is_valid`
- `"invalid"` uses in the formatter
- `AddInvalid` for `!has_value` in `inst_fingerprinter` (because the
cases it's called sound invalid-ish)
This introduces `calling_convention_param_ids`, a single block that
consolidates all the information that was being used by consumers of
`param_refs` and `implicit_param_refs`, in a form that's easier to
produce and typically easier to consume.
See also [this Discord
discussion](https://discord.com/channels/655572317891461132/655578254970716160/1300545448909738125)
regarding the decision to keep the return slot last in the SemIR calling
convention, even though it goes first in the LLVM calling convention.
---------
Co-authored-by: Jon Ross-Perkins <jperkins@google.com>
Also propagate the pattern IR along with the pattern-match IR, and use
it where appropriate.
Strictly speaking, some parts of the pattern-match IR are allocated
eagerly, while traversing the pattern's parse tree, but they still
aren't actually emitted until we traverse the associated pattern insts.
---------
Co-authored-by: Jon Ross-Perkins <jperkins@google.com>
Geoff RomerandRichard Smith
Chandler Carruthandjosh11b
Nicholas Bishop
