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Move self to the explicit () parameter list (proposal #7016) (#7272)

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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 commit is contained in:
Chandler Carruth
2026-06-10 15:30:43 +00:00
committed by GitHub
co-authored by josh11b
parent fb05da761f
commit 7871237c15
296 changed files with 6101 additions and 4899 deletions
Download Patch File Download Diff File Expand all files Collapse all files
toolchain/check/testdata/impl/using_invalid_interface.carbon
Vendored
+20 -20
View File
@@ -19,14 +19,14 @@ class ArgToI(T:! I) {}
interface IMisuse {
let Arg:! type;
// CHECK:STDERR: fail_invalid_interface.carbon:[[@LINE+7]]:26: error: cannot convert type `Arg` into type implementing `I` [ConversionFailureTypeToFacet]
// CHECK:STDERR: fn Op[self: Self]() -> ArgToI(Arg);
// CHECK:STDERR: ^~~~~~~~~~~
// CHECK:STDERR: fail_invalid_interface.carbon:[[@LINE+7]]:18: error: cannot convert type `Arg` into type implementing `I` [ConversionFailureTypeToFacet]
// CHECK:STDERR: fn Op(self) -> ArgToI(Arg);
// CHECK:STDERR: ^~~~~~~~~~~
// CHECK:STDERR: fail_invalid_interface.carbon:[[@LINE-7]]:14: note: initializing generic parameter `T` declared here [InitializingGenericParam]
// CHECK:STDERR: class ArgToI(T:! I) {}
// CHECK:STDERR: ^~~~~
// CHECK:STDERR:
fn Op[self: Self]() -> ArgToI(Arg);
fn Op(self) -> ArgToI(Arg);
}
// --- fail_misusing_invalid_interface.carbon
@@ -40,23 +40,23 @@ class C {
// CHECK:STDERR: ^
// CHECK:STDERR:
impl as IMisuse where .Arg = T {
// CHECK:STDERR: fail_misusing_invalid_interface.carbon:[[@LINE+4]]:42: error: name `T` not found [NameNotFound]
// CHECK:STDERR: fn Op[unused self: Self]() -> ArgToI(T) {
// CHECK:STDERR: ^
// CHECK:STDERR: fail_misusing_invalid_interface.carbon:[[@LINE+4]]:34: error: name `T` not found [NameNotFound]
// CHECK:STDERR: fn Op(unused self) -> ArgToI(T) {
// CHECK:STDERR: ^
// CHECK:STDERR:
fn Op[unused self: Self]() -> ArgToI(T) {
fn Op(unused self) -> ArgToI(T) {
return {};
}
}
}
// CHECK:STDERR: fail_misusing_invalid_interface.carbon:[[@LINE+8]]:21: error: missing object argument in method call [MissingObjectInMethodCall]
// CHECK:STDERR: fail_misusing_invalid_interface.carbon:[[@LINE+8]]:21: error: 0 arguments passed to function expecting 1 argument [CallArgCountMismatch]
// CHECK:STDERR: fn F(T:! IMisuse) { T.Op(); }
// CHECK:STDERR: ^~~~~~
// CHECK:STDERR: fail_misusing_invalid_interface.carbon:[[@LINE-21]]:1: in import [InImport]
// CHECK:STDERR: fail_invalid_interface.carbon:16:3: note: calling function declared here [InCallToFunction]
// CHECK:STDERR: fn Op[self: Self]() -> ArgToI(Arg);
// CHECK:STDERR: ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
// CHECK:STDERR: fail_invalid_interface.carbon:16:3: note: calling function declared here [InCallToEntity]
// CHECK:STDERR: fn Op(self) -> ArgToI(Arg);
// CHECK:STDERR: ^~~~~~~~~~~~~~~~~~~~~~~~~~~
// CHECK:STDERR:
fn F(T:! IMisuse) { T.Op(); }
@@ -84,27 +84,27 @@ class ArgC {}
class C {
impl as IMisuse where .Arg = ArgC {
// CHECK:STDERR: fail_using_invalid_interface.carbon:[[@LINE+8]]:35: error: cannot convert type `ArgC` into type implementing `I` [ConversionFailureTypeToFacet]
// CHECK:STDERR: fn Op[unused self: Self]() -> ArgToI(ArgC) {
// CHECK:STDERR: ^~~~~~~~~~~~
// CHECK:STDERR: fail_using_invalid_interface.carbon:[[@LINE+8]]:27: error: cannot convert type `ArgC` into type implementing `I` [ConversionFailureTypeToFacet]
// CHECK:STDERR: fn Op(unused self) -> ArgToI(ArgC) {
// CHECK:STDERR: ^~~~~~~~~~~~
// CHECK:STDERR: fail_using_invalid_interface.carbon:[[@LINE-9]]:1: in import [InImport]
// CHECK:STDERR: fail_invalid_interface.carbon:5:14: note: initializing generic parameter `T` declared here [InitializingGenericParam]
// CHECK:STDERR: class ArgToI(T:! I) {}
// CHECK:STDERR: ^~~~~
// CHECK:STDERR:
fn Op[unused self: Self]() -> ArgToI(ArgC) {
fn Op(unused self) -> ArgToI(ArgC) {
return {};
}
}
}
// CHECK:STDERR: fail_using_invalid_interface.carbon:[[@LINE+8]]:21: error: missing object argument in method call [MissingObjectInMethodCall]
// CHECK:STDERR: fail_using_invalid_interface.carbon:[[@LINE+8]]:21: error: 0 arguments passed to function expecting 1 argument [CallArgCountMismatch]
// CHECK:STDERR: fn F(T:! IMisuse) { T.Op(); }
// CHECK:STDERR: ^~~~~~
// CHECK:STDERR: fail_using_invalid_interface.carbon:[[@LINE-23]]:1: in import [InImport]
// CHECK:STDERR: fail_invalid_interface.carbon:16:3: note: calling function declared here [InCallToFunction]
// CHECK:STDERR: fn Op[self: Self]() -> ArgToI(Arg);
// CHECK:STDERR: ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
// CHECK:STDERR: fail_invalid_interface.carbon:16:3: note: calling function declared here [InCallToEntity]
// CHECK:STDERR: fn Op(self) -> ArgToI(Arg);
// CHECK:STDERR: ^~~~~~~~~~~~~~~~~~~~~~~~~~~
// CHECK:STDERR:
fn F(T:! IMisuse) { T.Op(); }