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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 `}`.
96 lines
3.7 KiB
C++
96 lines
3.7 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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auto HandlePattern(Context& context) -> void {
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auto state = context.PopState();
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switch (context.PositionKind()) {
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case Lex::TokenKind::OpenParen:
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context.PushStateForPattern(
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StateKind::PatternListAsTuple, state.in_var_pattern,
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state.in_unused_pattern, state.in_field_shorthand_pattern,
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state.binding_context, state.ambient_precedence);
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break;
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case Lex::TokenKind::OpenCurlyBrace:
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context.PushStateForPattern(
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StateKind::PatternListAsStruct, state.in_var_pattern,
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state.in_unused_pattern, state.in_field_shorthand_pattern,
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state.binding_context, state.ambient_precedence);
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break;
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case Lex::TokenKind::Var:
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context.PushStateForPattern(
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StateKind::VariablePattern, state.in_var_pattern,
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state.in_unused_pattern, state.in_field_shorthand_pattern,
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state.binding_context, state.ambient_precedence);
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break;
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case Lex::TokenKind::Unused:
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context.PushStateForPattern(
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StateKind::UnusedPattern, state.in_var_pattern,
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state.in_unused_pattern, state.in_field_shorthand_pattern,
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state.binding_context, state.ambient_precedence);
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break;
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case Lex::TokenKind::Template:
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case Lex::TokenKind::Generic:
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case Lex::TokenKind::Runtime:
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case Lex::TokenKind::Ref:
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// `self` is always a binding, even when its type is omitted (and so is not
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// followed by a `:`).
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case Lex::TokenKind::SelfValueIdentifier:
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context.PushStateForPattern(
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StateKind::BindingPattern, state.in_var_pattern,
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state.in_unused_pattern, state.in_field_shorthand_pattern,
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state.binding_context, state.ambient_precedence);
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break;
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default:
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if (context.PositionKind().is_word() &&
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context.PositionKind(Lookahead::NextToken)
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.is_binding_pattern_operator()) {
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context.PushStateForPattern(
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StateKind::BindingPattern, state.in_var_pattern,
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state.in_unused_pattern, state.in_field_shorthand_pattern,
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state.binding_context, state.ambient_precedence);
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break;
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}
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context.PushStateForPattern(
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StateKind::ExprPattern, state.in_var_pattern, state.in_unused_pattern,
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state.in_field_shorthand_pattern, state.binding_context,
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state.ambient_precedence);
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context.PushStateForExpr(state.ambient_precedence);
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break;
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}
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}
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auto HandleExprPattern(Context& context) -> void {
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auto state = context.PopState();
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// If we parsed an expression followed by a binding operator, we most likely
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// have a malformed attempt to introduce a binding pattern that we interpreted
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// as an expression pattern, so diagnose that here rather than diagnosing a
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// missing `;` at an outer level.
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if (context.PositionKind().is_binding_pattern_operator()) {
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if (!state.has_error) {
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CARBON_DIAGNOSTIC(ExpectedBindingName, Error,
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"unexpected expression before {0} in binding pattern",
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Lex::TokenKind);
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// TODO: Underline the parsed expression.
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context.emitter().Emit(*context.position(), ExpectedBindingName,
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context.PositionKind());
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state.has_error = true;
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}
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context.Consume();
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// It'd be nice to skip the type expression here too, but we can't determine
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// the end of it.
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}
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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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