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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
48 lines
1.4 KiB
Plaintext
48 lines
1.4 KiB
Plaintext
// Part of the Carbon Language project, under the Apache License v2.0 with LLVM
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// Exceptions. See /LICENSE for license information.
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// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
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// TODO: This library is not part of the design. Either write a matching
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// proposal or remove this.
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package Core library "range";
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import library "prelude/destroy";
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import library "prelude/iterate";
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import library "prelude/operators/arithmetic";
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import library "prelude/operators/as";
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import library "prelude/operators/comparison";
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import library "prelude/types/int";
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import library "prelude/types/int_literal";
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import library "prelude/types/optional";
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class IntRange(N: IntLiteral) {
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fn Make(start: Int(N), end: Int(N)) -> Self {
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return {.start = start, .end = end};
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}
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impl as Iterate where .CursorType = Int(N) and .ElementType = Int(N) {
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fn NewCursor(self) -> Int(N) { return self.start; }
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fn Next(self, cursor: Int(N)*) -> Optional(Int(N)) {
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var value: Int(N) = *cursor;
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if (value < self.end) {
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++*cursor;
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return Optional(Int(N)).Some(value);
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} else {
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return Optional(Int(N)).None();
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}
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}
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}
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private var start: Int(N);
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private var end: Int(N);
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}
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fn Range(end: i32) -> IntRange(32) {
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return IntRange(32).Make(0, end);
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}
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fn InclusiveRange(start: i32, end: i32) -> IntRange(32) {
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return IntRange(32).Make(start, end + 1);
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}
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