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Replace :! binding syntax with phase keywords and contextual defaults (#7479)

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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 commit is contained in:
Chandler Carruth
2026-07-11 01:22:44 +00:00
committed by GitHub
parent bf106c3b4b
commit 8be274cf60
482 changed files with 16917 additions and 16226 deletions
Download Patch File Download Diff File Expand all files Collapse all files
toolchain/parse/testdata/generics/interface/associated_constants.carbon
Vendored
+12 -12
View File
@@ -13,9 +13,9 @@
library "[[@TEST_NAME]]";
interface I {
let T:! type;
final let I:! i32;
default let D:! bool;
let T: type;
final let I: i32;
default let D: bool;
}
// --- initializer.carbon
@@ -23,9 +23,9 @@ interface I {
library "[[@TEST_NAME]]";
interface I {
let T:! type = (i32, i32);
final let I:! i32 = 42;
default let D:! bool = false;
let T: type = (i32, i32);
final let I: i32 = 42;
default let D: bool = false;
}
// CHECK:STDOUT: - filename: associated_constants.carbon
@@ -40,19 +40,19 @@ interface I {
// CHECK:STDOUT: {kind: 'AssociatedConstantIntroducer', text: 'let'},
// CHECK:STDOUT: {kind: 'IdentifierNameNotBeforeSignature', text: 'T'},
// CHECK:STDOUT: {kind: 'TypeTypeLiteral', text: 'type'},
// CHECK:STDOUT: {kind: 'AssociatedConstantNameAndType', text: ':!', subtree_size: 3},
// CHECK:STDOUT: {kind: 'AssociatedConstantNameAndType', text: ':', subtree_size: 3},
// CHECK:STDOUT: {kind: 'AssociatedConstantDecl', text: ';', subtree_size: 5},
// CHECK:STDOUT: {kind: 'AssociatedConstantIntroducer', text: 'let'},
// CHECK:STDOUT: {kind: 'FinalModifier', text: 'final'},
// CHECK:STDOUT: {kind: 'IdentifierNameNotBeforeSignature', text: 'I'},
// CHECK:STDOUT: {kind: 'IntTypeLiteral', text: 'i32'},
// CHECK:STDOUT: {kind: 'AssociatedConstantNameAndType', text: ':!', subtree_size: 3},
// CHECK:STDOUT: {kind: 'AssociatedConstantNameAndType', text: ':', subtree_size: 3},
// CHECK:STDOUT: {kind: 'AssociatedConstantDecl', text: ';', subtree_size: 6},
// CHECK:STDOUT: {kind: 'AssociatedConstantIntroducer', text: 'let'},
// CHECK:STDOUT: {kind: 'DefaultModifier', text: 'default'},
// CHECK:STDOUT: {kind: 'IdentifierNameNotBeforeSignature', text: 'D'},
// CHECK:STDOUT: {kind: 'BoolTypeLiteral', text: 'bool'},
// CHECK:STDOUT: {kind: 'AssociatedConstantNameAndType', text: ':!', subtree_size: 3},
// CHECK:STDOUT: {kind: 'AssociatedConstantNameAndType', text: ':', subtree_size: 3},
// CHECK:STDOUT: {kind: 'AssociatedConstantDecl', text: ';', subtree_size: 6},
// CHECK:STDOUT: {kind: 'InterfaceDefinition', text: '}', subtree_size: 21},
// CHECK:STDOUT: {kind: 'FileEnd', text: ''},
@@ -69,7 +69,7 @@ interface I {
// CHECK:STDOUT: {kind: 'AssociatedConstantIntroducer', text: 'let'},
// CHECK:STDOUT: {kind: 'IdentifierNameNotBeforeSignature', text: 'T'},
// CHECK:STDOUT: {kind: 'TypeTypeLiteral', text: 'type'},
// CHECK:STDOUT: {kind: 'AssociatedConstantNameAndType', text: ':!', subtree_size: 3},
// CHECK:STDOUT: {kind: 'AssociatedConstantNameAndType', text: ':', subtree_size: 3},
// CHECK:STDOUT: {kind: 'AssociatedConstantInitializer', text: '='},
// CHECK:STDOUT: {kind: 'TupleLiteralStart', text: '('},
// CHECK:STDOUT: {kind: 'IntTypeLiteral', text: 'i32'},
@@ -81,7 +81,7 @@ interface I {
// CHECK:STDOUT: {kind: 'FinalModifier', text: 'final'},
// CHECK:STDOUT: {kind: 'IdentifierNameNotBeforeSignature', text: 'I'},
// CHECK:STDOUT: {kind: 'IntTypeLiteral', text: 'i32'},
// CHECK:STDOUT: {kind: 'AssociatedConstantNameAndType', text: ':!', subtree_size: 3},
// CHECK:STDOUT: {kind: 'AssociatedConstantNameAndType', text: ':', subtree_size: 3},
// CHECK:STDOUT: {kind: 'AssociatedConstantInitializer', text: '='},
// CHECK:STDOUT: {kind: 'IntLiteral', text: '42'},
// CHECK:STDOUT: {kind: 'AssociatedConstantDecl', text: ';', subtree_size: 8},
@@ -89,7 +89,7 @@ interface I {
// CHECK:STDOUT: {kind: 'DefaultModifier', text: 'default'},
// CHECK:STDOUT: {kind: 'IdentifierNameNotBeforeSignature', text: 'D'},
// CHECK:STDOUT: {kind: 'BoolTypeLiteral', text: 'bool'},
// CHECK:STDOUT: {kind: 'AssociatedConstantNameAndType', text: ':!', subtree_size: 3},
// CHECK:STDOUT: {kind: 'AssociatedConstantNameAndType', text: ':', subtree_size: 3},
// CHECK:STDOUT: {kind: 'AssociatedConstantInitializer', text: '='},
// CHECK:STDOUT: {kind: 'BoolLiteralFalse', text: 'false'},
// CHECK:STDOUT: {kind: 'AssociatedConstantDecl', text: ';', subtree_size: 8},