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oli-ej
a683fb574b
Implements parsing of struct patterns as per https://github.com/carbon-language/carbon-lang/issues/6680. This handles the full and short syntax given in the [design doc](https://github.com/carbon-language/carbon-lang/blob/trunk/docs/design/pattern_matching.md#struct-patterns), but the handling of the shorthand syntax may need to change as I move on to implementing Check support (currently the shorthand is represented as one of `LetBindingPattern`, `VarBindingPattern`, or `VariablePattern`). This implementation assumes that the answer to https://github.com/carbon-language/carbon-lang/issues/7404 is that trailing commas are allowed in the struct pattern, except for the case where an `_` is present, in which case the next token must be the closing brace `}`.
121 lines
4.1 KiB
C++
121 lines
4.1 KiB
C++
// 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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#include "toolchain/parse/context.h"
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#include "toolchain/parse/handle.h"
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namespace Carbon::Parse {
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// Handles VarAs(Regular|Returned).
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static auto HandleVar(Context& context, StateKind finish_state_kind,
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Lex::TokenIndex returned_token = Lex::TokenIndex::None)
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-> void {
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auto state = context.PopState();
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// The finished variable declaration will start at the `var` or `returned`.
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context.PushState(state, finish_state_kind);
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// TODO: is there a cleaner way to give VarAfterPattern access to the `var`
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// token?
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state.token = *(context.position() - 1);
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context.PushState(state, StateKind::VarAfterPattern);
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if (returned_token.has_value()) {
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context.AddLeafNode(NodeKind::ReturnedModifier, returned_token);
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}
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context.PushStateForPattern(StateKind::Pattern, /*in_var_pattern=*/true,
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/*in_unused_pattern=*/false,
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/*in_field_shorthand_pattern=*/false,
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BindingContext::ExplicitParam,
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PrecedenceGroup::ForTopLevelPattern());
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}
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auto HandleVarAsRegular(Context& context) -> void {
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HandleVar(context, StateKind::VarFinish);
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}
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auto HandleVarAsReturned(Context& context) -> void {
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auto returned_token = context.Consume();
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if (!context.PositionIs(Lex::TokenKind::Var)) {
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CARBON_DIAGNOSTIC(ExpectedVarAfterReturned, Error,
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"expected `var` after `returned`");
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context.emitter().Emit(*context.position(), ExpectedVarAfterReturned);
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context.AddLeafNode(NodeKind::EmptyDecl,
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context.SkipPastLikelyEnd(returned_token),
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/*has_error=*/true);
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context.PopAndDiscardState();
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return;
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}
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context.AddLeafNode(NodeKind::VariableIntroducer, context.Consume());
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HandleVar(context, StateKind::VarFinish, returned_token);
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}
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auto HandleVarAfterPattern(Context& context) -> void {
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auto state = context.PopState();
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if (state.has_error) {
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if (auto after_pattern =
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context.FindNextOf({Lex::TokenKind::Equal, Lex::TokenKind::Semi})) {
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context.SkipTo(*after_pattern);
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}
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}
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context.AddNode(NodeKind::VariablePattern, state.token, state.has_error);
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if (context.PositionIs(Lex::TokenKind::Equal)) {
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context.AddLeafNode(NodeKind::VariableInitializer,
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context.ConsumeChecked(Lex::TokenKind::Equal));
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context.PushState(StateKind::Expr);
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}
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}
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auto HandleVarFinish(Context& context) -> void {
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auto state = context.PopState();
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auto end_token = state.token;
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if (context.PositionIs(Lex::TokenKind::Semi)) {
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end_token = context.Consume();
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} else {
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// TODO: Disambiguate between statement and member declaration.
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context.DiagnoseExpectedDeclSemi(Lex::TokenKind::Var);
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state.has_error = true;
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end_token = context.SkipPastLikelyEnd(state.token);
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}
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context.AddNode(NodeKind::VariableDecl, end_token, state.has_error);
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}
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auto HandleVariablePattern(Context& context) -> void {
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auto state = context.PopState();
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if (state.in_var_pattern) {
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CARBON_DIAGNOSTIC(NestedVar, Error, "`var` nested within another `var`");
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context.emitter().Emit(*context.position(), NestedVar);
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state.has_error = true;
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}
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state.kind = StateKind::FinishVariablePattern;
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context.PushState(state);
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context.ConsumeChecked(Lex::TokenKind::Var);
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// A `var` binding is always runtime, regardless of the enclosing context.
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context.PushStateForPattern(
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StateKind::Pattern, /*in_var_pattern=*/true, state.in_unused_pattern,
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state.in_field_shorthand_pattern, BindingContext::ExplicitParam,
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state.ambient_precedence);
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}
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auto HandleFinishVariablePattern(Context& context) -> void {
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auto state = context.PopState();
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context.AddNode(NodeKind::VariablePattern, state.token, state.has_error);
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// Propagate errors to the parent state so that they can take different
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// actions on invalid patterns.
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if (state.has_error) {
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context.ReturnErrorOnState();
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}
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}
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} // namespace Carbon::Parse
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