mirror of
https://github.com/carbon-language/carbon-lang.git
synced 2026-09-24 22:02:23 +01:00
Chandler Carruth
8be274cf60
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
38 lines
1.3 KiB
C++
38 lines
1.3 KiB
C++
// Part of the Carbon Language project, under the Apache License v2.0 with LLVM
|
|
// Exceptions. See /LICENSE for license information.
|
|
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
|
|
|
|
#include "toolchain/parse/context.h"
|
|
#include "toolchain/parse/handle.h"
|
|
|
|
namespace Carbon::Parse {
|
|
|
|
auto HandleUnusedPattern(Context& context) -> void {
|
|
auto state = context.PopState();
|
|
if (state.in_unused_pattern) {
|
|
CARBON_DIAGNOSTIC(NestedUnused, Error,
|
|
"`unused` nested within another `unused`");
|
|
context.emitter().Emit(*context.position(), NestedUnused);
|
|
state.has_error = true;
|
|
}
|
|
context.PushState(StateKind::FinishUnusedPattern);
|
|
context.ConsumeChecked(Lex::TokenKind::Unused);
|
|
|
|
context.PushStateForPattern(StateKind::Pattern, state.in_var_pattern,
|
|
/*in_unused_pattern=*/true, state.binding_context,
|
|
state.ambient_precedence);
|
|
}
|
|
|
|
auto HandleFinishUnusedPattern(Context& context) -> void {
|
|
auto state = context.PopState();
|
|
context.AddNode(NodeKind::UnusedPattern, state.token, state.has_error);
|
|
|
|
// Propagate errors to the parent state so that they can take different
|
|
// actions on invalid patterns.
|
|
if (state.has_error) {
|
|
context.ReturnErrorOnState();
|
|
}
|
|
}
|
|
|
|
} // namespace Carbon::Parse
|