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

Browse Source 
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/parse/testdata/generics/interface/basic.carbon
Vendored
+12 -15
View File
@@ -9,8 +9,8 @@
// TIP: bazel run //toolchain/testing:file_test -- --dump_output --file_tests=toolchain/parse/testdata/generics/interface/basic.carbon
interface Foo {
fn Add[self: Self](b: Self) -> Self;
fn Add[self: foo](b: Self) -> Self;
fn Add(self, b: Self) -> Self;
fn Add(self: foo, b: Self) -> Self;
}
// CHECK:STDOUT: - filename: basic.carbon
@@ -21,34 +21,31 @@ interface Foo {
// CHECK:STDOUT: {kind: 'InterfaceDefinitionStart', text: '{', subtree_size: 3},
// CHECK:STDOUT: {kind: 'FunctionIntroducer', text: 'fn'},
// CHECK:STDOUT: {kind: 'IdentifierNameMaybeBeforeSignature', text: 'Add'},
// CHECK:STDOUT: {kind: 'ImplicitParamListStart', text: '['},
// CHECK:STDOUT: {kind: 'SelfValueName', text: 'self'},
// CHECK:STDOUT: {kind: 'SelfTypeNameExpr', text: 'Self'},
// CHECK:STDOUT: {kind: 'LetBindingPattern', text: ':', subtree_size: 3},
// CHECK:STDOUT: {kind: 'ImplicitParamList', text: ']', subtree_size: 5},
// CHECK:STDOUT: {kind: 'ExplicitParamListStart', text: '('},
// CHECK:STDOUT: {kind: 'SelfValueName', text: 'self'},
// CHECK:STDOUT: {kind: 'SelfBindingPattern', text: 'self', subtree_size: 2},
// CHECK:STDOUT: {kind: 'PatternListComma', text: ','},
// CHECK:STDOUT: {kind: 'IdentifierNameNotBeforeSignature', text: 'b'},
// CHECK:STDOUT: {kind: 'SelfTypeNameExpr', text: 'Self'},
// CHECK:STDOUT: {kind: 'LetBindingPattern', text: ':', subtree_size: 3},
// CHECK:STDOUT: {kind: 'ExplicitParamList', text: ')', subtree_size: 5},
// CHECK:STDOUT: {kind: 'ExplicitParamList', text: ')', subtree_size: 8},
// CHECK:STDOUT: {kind: 'SelfTypeNameExpr', text: 'Self'},
// CHECK:STDOUT: {kind: 'ReturnType', text: '->', subtree_size: 2},
// CHECK:STDOUT: {kind: 'FunctionDecl', text: ';', subtree_size: 15},
// CHECK:STDOUT: {kind: 'FunctionDecl', text: ';', subtree_size: 13},
// CHECK:STDOUT: {kind: 'FunctionIntroducer', text: 'fn'},
// CHECK:STDOUT: {kind: 'IdentifierNameMaybeBeforeSignature', text: 'Add'},
// CHECK:STDOUT: {kind: 'ImplicitParamListStart', text: '['},
// CHECK:STDOUT: {kind: 'ExplicitParamListStart', text: '('},
// CHECK:STDOUT: {kind: 'SelfValueName', text: 'self'},
// CHECK:STDOUT: {kind: 'IdentifierNameExpr', text: 'foo'},
// CHECK:STDOUT: {kind: 'LetBindingPattern', text: ':', subtree_size: 3},
// CHECK:STDOUT: {kind: 'ImplicitParamList', text: ']', subtree_size: 5},
// CHECK:STDOUT: {kind: 'ExplicitParamListStart', text: '('},
// CHECK:STDOUT: {kind: 'PatternListComma', text: ','},
// CHECK:STDOUT: {kind: 'IdentifierNameNotBeforeSignature', text: 'b'},
// CHECK:STDOUT: {kind: 'SelfTypeNameExpr', text: 'Self'},
// CHECK:STDOUT: {kind: 'LetBindingPattern', text: ':', subtree_size: 3},
// CHECK:STDOUT: {kind: 'ExplicitParamList', text: ')', subtree_size: 5},
// CHECK:STDOUT: {kind: 'ExplicitParamList', text: ')', subtree_size: 9},
// CHECK:STDOUT: {kind: 'SelfTypeNameExpr', text: 'Self'},
// CHECK:STDOUT: {kind: 'ReturnType', text: '->', subtree_size: 2},
// CHECK:STDOUT: {kind: 'FunctionDecl', text: ';', subtree_size: 15},
// CHECK:STDOUT: {kind: 'InterfaceDefinition', text: '}', subtree_size: 34},
// CHECK:STDOUT: {kind: 'FunctionDecl', text: ';', subtree_size: 14},
// CHECK:STDOUT: {kind: 'InterfaceDefinition', text: '}', subtree_size: 31},
// CHECK:STDOUT: {kind: 'FileEnd', text: ''},
// CHECK:STDOUT: ]
toolchain/parse/testdata/generics/interface/default_fn.carbon
Vendored
+13 -18
View File
@@ -9,10 +9,10 @@
// TIP: bazel run //toolchain/testing:file_test -- --dump_output --file_tests=toolchain/parse/testdata/generics/interface/default_fn.carbon
interface Foo {
fn Scale[self: Self](s: i32) -> Self;
fn Scale(self, s: i32) -> Self;
// Default definition of `Invert` calls `Scale`.
default fn Invert[self: Self]() -> Self {
default fn Invert(self) -> Self {
return self.Scale(-1);
}
}
@@ -25,32 +25,27 @@ interface Foo {
// CHECK:STDOUT: {kind: 'InterfaceDefinitionStart', text: '{', subtree_size: 3},
// CHECK:STDOUT: {kind: 'FunctionIntroducer', text: 'fn'},
// CHECK:STDOUT: {kind: 'IdentifierNameMaybeBeforeSignature', text: 'Scale'},
// CHECK:STDOUT: {kind: 'ImplicitParamListStart', text: '['},
// CHECK:STDOUT: {kind: 'SelfValueName', text: 'self'},
// CHECK:STDOUT: {kind: 'SelfTypeNameExpr', text: 'Self'},
// CHECK:STDOUT: {kind: 'LetBindingPattern', text: ':', subtree_size: 3},
// CHECK:STDOUT: {kind: 'ImplicitParamList', text: ']', subtree_size: 5},
// CHECK:STDOUT: {kind: 'ExplicitParamListStart', text: '('},
// CHECK:STDOUT: {kind: 'SelfValueName', text: 'self'},
// CHECK:STDOUT: {kind: 'SelfBindingPattern', text: 'self', subtree_size: 2},
// CHECK:STDOUT: {kind: 'PatternListComma', text: ','},
// CHECK:STDOUT: {kind: 'IdentifierNameNotBeforeSignature', text: 's'},
// CHECK:STDOUT: {kind: 'IntTypeLiteral', text: 'i32'},
// CHECK:STDOUT: {kind: 'LetBindingPattern', text: ':', subtree_size: 3},
// CHECK:STDOUT: {kind: 'ExplicitParamList', text: ')', subtree_size: 5},
// CHECK:STDOUT: {kind: 'ExplicitParamList', text: ')', subtree_size: 8},
// CHECK:STDOUT: {kind: 'SelfTypeNameExpr', text: 'Self'},
// CHECK:STDOUT: {kind: 'ReturnType', text: '->', subtree_size: 2},
// CHECK:STDOUT: {kind: 'FunctionDecl', text: ';', subtree_size: 15},
// CHECK:STDOUT: {kind: 'FunctionDecl', text: ';', subtree_size: 13},
// CHECK:STDOUT: {kind: 'FunctionIntroducer', text: 'fn'},
// CHECK:STDOUT: {kind: 'DefaultModifier', text: 'default'},
// CHECK:STDOUT: {kind: 'IdentifierNameMaybeBeforeSignature', text: 'Invert'},
// CHECK:STDOUT: {kind: 'ImplicitParamListStart', text: '['},
// CHECK:STDOUT: {kind: 'SelfValueName', text: 'self'},
// CHECK:STDOUT: {kind: 'SelfTypeNameExpr', text: 'Self'},
// CHECK:STDOUT: {kind: 'LetBindingPattern', text: ':', subtree_size: 3},
// CHECK:STDOUT: {kind: 'ImplicitParamList', text: ']', subtree_size: 5},
// CHECK:STDOUT: {kind: 'ExplicitParamListStart', text: '('},
// CHECK:STDOUT: {kind: 'ExplicitParamList', text: ')', subtree_size: 2},
// CHECK:STDOUT: {kind: 'SelfValueName', text: 'self'},
// CHECK:STDOUT: {kind: 'SelfBindingPattern', text: 'self', subtree_size: 2},
// CHECK:STDOUT: {kind: 'ExplicitParamList', text: ')', subtree_size: 4},
// CHECK:STDOUT: {kind: 'SelfTypeNameExpr', text: 'Self'},
// CHECK:STDOUT: {kind: 'ReturnType', text: '->', subtree_size: 2},
// CHECK:STDOUT: {kind: 'FunctionDefinitionStart', text: '{', subtree_size: 13},
// CHECK:STDOUT: {kind: 'FunctionDefinitionStart', text: '{', subtree_size: 10},
// CHECK:STDOUT: {kind: 'ReturnStatementStart', text: 'return'},
// CHECK:STDOUT: {kind: 'SelfValueNameExpr', text: 'self'},
// CHECK:STDOUT: {kind: 'IdentifierNameNotBeforeSignature', text: 'Scale'},
@@ -60,7 +55,7 @@ interface Foo {
// CHECK:STDOUT: {kind: 'PrefixOperatorMinus', text: '-', subtree_size: 2},
// CHECK:STDOUT: {kind: 'CallExpr', text: ')', subtree_size: 7},
// CHECK:STDOUT: {kind: 'ReturnStatement', text: ';', subtree_size: 9},
// CHECK:STDOUT: {kind: 'FunctionDefinition', text: '}', subtree_size: 23},
// CHECK:STDOUT: {kind: 'InterfaceDefinition', text: '}', subtree_size: 42},
// CHECK:STDOUT: {kind: 'FunctionDefinition', text: '}', subtree_size: 20},
// CHECK:STDOUT: {kind: 'InterfaceDefinition', text: '}', subtree_size: 37},
// CHECK:STDOUT: {kind: 'FileEnd', text: ''},
// CHECK:STDOUT: ]
toolchain/parse/testdata/generics/interface/final_fn.carbon
Vendored
+14 -18
View File
@@ -9,8 +9,8 @@
// TIP: bazel run //toolchain/testing:file_test -- --dump_output --file_tests=toolchain/parse/testdata/generics/interface/final_fn.carbon
interface Order {
fn Less[self: Self](right: Self) -> bool;
final fn Greater[self: Self](right: Self) -> bool {
fn Less(self, right: Self) -> bool;
final fn Greater(self, right: Self) -> bool {
return right.Less(self);
}
}
@@ -23,35 +23,31 @@ interface Order {
// CHECK:STDOUT: {kind: 'InterfaceDefinitionStart', text: '{', subtree_size: 3},
// CHECK:STDOUT: {kind: 'FunctionIntroducer', text: 'fn'},
// CHECK:STDOUT: {kind: 'IdentifierNameMaybeBeforeSignature', text: 'Less'},
// CHECK:STDOUT: {kind: 'ImplicitParamListStart', text: '['},
// CHECK:STDOUT: {kind: 'SelfValueName', text: 'self'},
// CHECK:STDOUT: {kind: 'SelfTypeNameExpr', text: 'Self'},
// CHECK:STDOUT: {kind: 'LetBindingPattern', text: ':', subtree_size: 3},
// CHECK:STDOUT: {kind: 'ImplicitParamList', text: ']', subtree_size: 5},
// CHECK:STDOUT: {kind: 'ExplicitParamListStart', text: '('},
// CHECK:STDOUT: {kind: 'SelfValueName', text: 'self'},
// CHECK:STDOUT: {kind: 'SelfBindingPattern', text: 'self', subtree_size: 2},
// CHECK:STDOUT: {kind: 'PatternListComma', text: ','},
// CHECK:STDOUT: {kind: 'IdentifierNameNotBeforeSignature', text: 'right'},
// CHECK:STDOUT: {kind: 'SelfTypeNameExpr', text: 'Self'},
// CHECK:STDOUT: {kind: 'LetBindingPattern', text: ':', subtree_size: 3},
// CHECK:STDOUT: {kind: 'ExplicitParamList', text: ')', subtree_size: 5},
// CHECK:STDOUT: {kind: 'ExplicitParamList', text: ')', subtree_size: 8},
// CHECK:STDOUT: {kind: 'BoolTypeLiteral', text: 'bool'},
// CHECK:STDOUT: {kind: 'ReturnType', text: '->', subtree_size: 2},
// CHECK:STDOUT: {kind: 'FunctionDecl', text: ';', subtree_size: 15},
// CHECK:STDOUT: {kind: 'FunctionDecl', text: ';', subtree_size: 13},
// CHECK:STDOUT: {kind: 'FunctionIntroducer', text: 'fn'},
// CHECK:STDOUT: {kind: 'FinalModifier', text: 'final'},
// CHECK:STDOUT: {kind: 'IdentifierNameMaybeBeforeSignature', text: 'Greater'},
// CHECK:STDOUT: {kind: 'ImplicitParamListStart', text: '['},
// CHECK:STDOUT: {kind: 'SelfValueName', text: 'self'},
// CHECK:STDOUT: {kind: 'SelfTypeNameExpr', text: 'Self'},
// CHECK:STDOUT: {kind: 'LetBindingPattern', text: ':', subtree_size: 3},
// CHECK:STDOUT: {kind: 'ImplicitParamList', text: ']', subtree_size: 5},
// CHECK:STDOUT: {kind: 'ExplicitParamListStart', text: '('},
// CHECK:STDOUT: {kind: 'SelfValueName', text: 'self'},
// CHECK:STDOUT: {kind: 'SelfBindingPattern', text: 'self', subtree_size: 2},
// CHECK:STDOUT: {kind: 'PatternListComma', text: ','},
// CHECK:STDOUT: {kind: 'IdentifierNameNotBeforeSignature', text: 'right'},
// CHECK:STDOUT: {kind: 'SelfTypeNameExpr', text: 'Self'},
// CHECK:STDOUT: {kind: 'LetBindingPattern', text: ':', subtree_size: 3},
// CHECK:STDOUT: {kind: 'ExplicitParamList', text: ')', subtree_size: 5},
// CHECK:STDOUT: {kind: 'ExplicitParamList', text: ')', subtree_size: 8},
// CHECK:STDOUT: {kind: 'BoolTypeLiteral', text: 'bool'},
// CHECK:STDOUT: {kind: 'ReturnType', text: '->', subtree_size: 2},
// CHECK:STDOUT: {kind: 'FunctionDefinitionStart', text: '{', subtree_size: 16},
// CHECK:STDOUT: {kind: 'FunctionDefinitionStart', text: '{', subtree_size: 14},
// CHECK:STDOUT: {kind: 'ReturnStatementStart', text: 'return'},
// CHECK:STDOUT: {kind: 'IdentifierNameExpr', text: 'right'},
// CHECK:STDOUT: {kind: 'IdentifierNameNotBeforeSignature', text: 'Less'},
@@ -60,7 +56,7 @@ interface Order {
// CHECK:STDOUT: {kind: 'SelfValueNameExpr', text: 'self'},
// CHECK:STDOUT: {kind: 'CallExpr', text: ')', subtree_size: 6},
// CHECK:STDOUT: {kind: 'ReturnStatement', text: ';', subtree_size: 8},
// CHECK:STDOUT: {kind: 'FunctionDefinition', text: '}', subtree_size: 25},
// CHECK:STDOUT: {kind: 'InterfaceDefinition', text: '}', subtree_size: 44},
// CHECK:STDOUT: {kind: 'FunctionDefinition', text: '}', subtree_size: 23},
// CHECK:STDOUT: {kind: 'InterfaceDefinition', text: '}', subtree_size: 40},
// CHECK:STDOUT: {kind: 'FileEnd', text: ''},
// CHECK:STDOUT: ]
toolchain/parse/testdata/generics/interface/final_member_definition.carbon
Vendored
+9 -11
View File
@@ -9,7 +9,7 @@
// TIP: bazel run //toolchain/testing:file_test -- --dump_output --file_tests=toolchain/parse/testdata/generics/interface/final_member_definition.carbon
interface Foo {
final fn Add[unused self: Self](b: Self) -> Self {
final fn Add(unused self, b: Self) -> Self {
print("Allowed.");
}
}
@@ -23,26 +23,24 @@ interface Foo {
// CHECK:STDOUT: {kind: 'FunctionIntroducer', text: 'fn'},
// CHECK:STDOUT: {kind: 'FinalModifier', text: 'final'},
// CHECK:STDOUT: {kind: 'IdentifierNameMaybeBeforeSignature', text: 'Add'},
// CHECK:STDOUT: {kind: 'ImplicitParamListStart', text: '['},
// CHECK:STDOUT: {kind: 'SelfValueName', text: 'self'},
// CHECK:STDOUT: {kind: 'SelfTypeNameExpr', text: 'Self'},
// CHECK:STDOUT: {kind: 'LetBindingPattern', text: ':', subtree_size: 3},
// CHECK:STDOUT: {kind: 'UnusedPattern', text: 'unused', subtree_size: 4},
// CHECK:STDOUT: {kind: 'ImplicitParamList', text: ']', subtree_size: 6},
// CHECK:STDOUT: {kind: 'ExplicitParamListStart', text: '('},
// CHECK:STDOUT: {kind: 'SelfValueName', text: 'self'},
// CHECK:STDOUT: {kind: 'SelfBindingPattern', text: 'self', subtree_size: 2},
// CHECK:STDOUT: {kind: 'UnusedPattern', text: 'unused', subtree_size: 3},
// CHECK:STDOUT: {kind: 'PatternListComma', text: ','},
// CHECK:STDOUT: {kind: 'IdentifierNameNotBeforeSignature', text: 'b'},
// CHECK:STDOUT: {kind: 'SelfTypeNameExpr', text: 'Self'},
// CHECK:STDOUT: {kind: 'LetBindingPattern', text: ':', subtree_size: 3},
// CHECK:STDOUT: {kind: 'ExplicitParamList', text: ')', subtree_size: 5},
// CHECK:STDOUT: {kind: 'ExplicitParamList', text: ')', subtree_size: 9},
// CHECK:STDOUT: {kind: 'SelfTypeNameExpr', text: 'Self'},
// CHECK:STDOUT: {kind: 'ReturnType', text: '->', subtree_size: 2},
// CHECK:STDOUT: {kind: 'FunctionDefinitionStart', text: '{', subtree_size: 17},
// CHECK:STDOUT: {kind: 'FunctionDefinitionStart', text: '{', subtree_size: 15},
// CHECK:STDOUT: {kind: 'IdentifierNameExpr', text: 'print'},
// CHECK:STDOUT: {kind: 'CallExprStart', text: '(', subtree_size: 2},
// CHECK:STDOUT: {kind: 'StringLiteral', text: '"Allowed."'},
// CHECK:STDOUT: {kind: 'CallExpr', text: ')', subtree_size: 4},
// CHECK:STDOUT: {kind: 'ExprStatement', text: ';', subtree_size: 5},
// CHECK:STDOUT: {kind: 'FunctionDefinition', text: '}', subtree_size: 23},
// CHECK:STDOUT: {kind: 'InterfaceDefinition', text: '}', subtree_size: 27},
// CHECK:STDOUT: {kind: 'FunctionDefinition', text: '}', subtree_size: 21},
// CHECK:STDOUT: {kind: 'InterfaceDefinition', text: '}', subtree_size: 25},
// CHECK:STDOUT: {kind: 'FileEnd', text: ''},
// CHECK:STDOUT: ]
toolchain/parse/testdata/generics/interface/self_ref.carbon
Vendored
+12 -15
View File
@@ -9,8 +9,8 @@
// TIP: bazel run //toolchain/testing:file_test -- --dump_output --file_tests=toolchain/parse/testdata/generics/interface/self_ref.carbon
interface Foo {
fn Sub[ref self: Self](b: Self) -> Self;
fn Sub[ref self: foo](b: Self) -> Self;
fn Sub(ref self, b: Self) -> Self;
fn Sub(ref self: foo, b: Self) -> Self;
}
// CHECK:STDOUT: - filename: self_ref.carbon
@@ -21,36 +21,33 @@ interface Foo {
// CHECK:STDOUT: {kind: 'InterfaceDefinitionStart', text: '{', subtree_size: 3},
// CHECK:STDOUT: {kind: 'FunctionIntroducer', text: 'fn'},
// CHECK:STDOUT: {kind: 'IdentifierNameMaybeBeforeSignature', text: 'Sub'},
// CHECK:STDOUT: {kind: 'ImplicitParamListStart', text: '['},
// CHECK:STDOUT: {kind: 'ExplicitParamListStart', text: '('},
// CHECK:STDOUT: {kind: 'SelfValueName', text: 'self'},
// CHECK:STDOUT: {kind: 'RefBindingName', text: 'ref', subtree_size: 2},
// CHECK:STDOUT: {kind: 'SelfTypeNameExpr', text: 'Self'},
// CHECK:STDOUT: {kind: 'LetBindingPattern', text: ':', subtree_size: 4},
// CHECK:STDOUT: {kind: 'ImplicitParamList', text: ']', subtree_size: 6},
// CHECK:STDOUT: {kind: 'ExplicitParamListStart', text: '('},
// CHECK:STDOUT: {kind: 'SelfBindingPattern', text: 'self', subtree_size: 3},
// CHECK:STDOUT: {kind: 'PatternListComma', text: ','},
// CHECK:STDOUT: {kind: 'IdentifierNameNotBeforeSignature', text: 'b'},
// CHECK:STDOUT: {kind: 'SelfTypeNameExpr', text: 'Self'},
// CHECK:STDOUT: {kind: 'LetBindingPattern', text: ':', subtree_size: 3},
// CHECK:STDOUT: {kind: 'ExplicitParamList', text: ')', subtree_size: 5},
// CHECK:STDOUT: {kind: 'ExplicitParamList', text: ')', subtree_size: 9},
// CHECK:STDOUT: {kind: 'SelfTypeNameExpr', text: 'Self'},
// CHECK:STDOUT: {kind: 'ReturnType', text: '->', subtree_size: 2},
// CHECK:STDOUT: {kind: 'FunctionDecl', text: ';', subtree_size: 16},
// CHECK:STDOUT: {kind: 'FunctionDecl', text: ';', subtree_size: 14},
// CHECK:STDOUT: {kind: 'FunctionIntroducer', text: 'fn'},
// CHECK:STDOUT: {kind: 'IdentifierNameMaybeBeforeSignature', text: 'Sub'},
// CHECK:STDOUT: {kind: 'ImplicitParamListStart', text: '['},
// CHECK:STDOUT: {kind: 'ExplicitParamListStart', text: '('},
// CHECK:STDOUT: {kind: 'SelfValueName', text: 'self'},
// CHECK:STDOUT: {kind: 'RefBindingName', text: 'ref', subtree_size: 2},
// CHECK:STDOUT: {kind: 'IdentifierNameExpr', text: 'foo'},
// CHECK:STDOUT: {kind: 'LetBindingPattern', text: ':', subtree_size: 4},
// CHECK:STDOUT: {kind: 'ImplicitParamList', text: ']', subtree_size: 6},
// CHECK:STDOUT: {kind: 'ExplicitParamListStart', text: '('},
// CHECK:STDOUT: {kind: 'PatternListComma', text: ','},
// CHECK:STDOUT: {kind: 'IdentifierNameNotBeforeSignature', text: 'b'},
// CHECK:STDOUT: {kind: 'SelfTypeNameExpr', text: 'Self'},
// CHECK:STDOUT: {kind: 'LetBindingPattern', text: ':', subtree_size: 3},
// CHECK:STDOUT: {kind: 'ExplicitParamList', text: ')', subtree_size: 5},
// CHECK:STDOUT: {kind: 'ExplicitParamList', text: ')', subtree_size: 10},
// CHECK:STDOUT: {kind: 'SelfTypeNameExpr', text: 'Self'},
// CHECK:STDOUT: {kind: 'ReturnType', text: '->', subtree_size: 2},
// CHECK:STDOUT: {kind: 'FunctionDecl', text: ';', subtree_size: 16},
// CHECK:STDOUT: {kind: 'InterfaceDefinition', text: '}', subtree_size: 36},
// CHECK:STDOUT: {kind: 'FunctionDecl', text: ';', subtree_size: 15},
// CHECK:STDOUT: {kind: 'InterfaceDefinition', text: '}', subtree_size: 33},
// CHECK:STDOUT: {kind: 'FileEnd', text: ''},
// CHECK:STDOUT: ]