mirror of
https://github.com/carbon-language/carbon-lang.git
synced 2026-09-27 14:20:23 +01:00
Chandler CarruthandJon Ross-Perkins
94cf343b05
LLVM's bazel build has changed a bit, so this updates the tree for that. LLVM is also moving `llvm::Optional` to match the standard API, but it seemed simpler to just switch to `std::optional`. Co-authored-by: Jon Ross-Perkins <jperkins@google.com>
102 lines
3.4 KiB
C++
102 lines
3.4 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
|
|
|
|
#ifndef CARBON_TOOLCHAIN_PARSER_PRECEDENCE_H_
|
|
#define CARBON_TOOLCHAIN_PARSER_PRECEDENCE_H_
|
|
|
|
#include <optional>
|
|
|
|
#include "toolchain/lexer/token_kind.h"
|
|
|
|
namespace Carbon {
|
|
|
|
// Given two operators `$` and `@`, and an expression `a $ b @ c`, how should
|
|
// the expression be parsed?
|
|
enum class OperatorPriority : int8_t {
|
|
// The left operator has higher precedence: `(a $ b) @ c`.
|
|
LeftFirst = -1,
|
|
// The expression is ambiguous.
|
|
Ambiguous = 0,
|
|
// The right operator has higher precedence: `a $ (b @ c)`.
|
|
RightFirst = 1,
|
|
};
|
|
|
|
enum class Associativity : int8_t {
|
|
LeftToRight = -1,
|
|
None = 0,
|
|
RightToLeft = 1
|
|
};
|
|
|
|
// A precedence group associated with an operator or expression.
|
|
class PrecedenceGroup {
|
|
public:
|
|
struct Trailing;
|
|
|
|
// Objects of this type should only be constructed using the static factory
|
|
// functions below.
|
|
PrecedenceGroup() = delete;
|
|
|
|
// Get the sentinel precedence level for a postfix expression. All operators
|
|
// should have lower precedence than this.
|
|
static auto ForPostfixExpression() -> PrecedenceGroup;
|
|
|
|
// Get the sentinel precedence level for a top-level expression context. All
|
|
// operators should have higher precedence than this.
|
|
static auto ForTopLevelExpression() -> PrecedenceGroup;
|
|
|
|
// Get the precedence level at which to parse a type expression. All type
|
|
// operators should have higher precedence than this.
|
|
static auto ForType() -> PrecedenceGroup;
|
|
|
|
// Look up the operator information of the given prefix operator token, or
|
|
// return std::nullopt if the given token is not a prefix operator.
|
|
static auto ForLeading(TokenKind kind) -> std::optional<PrecedenceGroup>;
|
|
|
|
// Look up the operator information of the given infix or postfix operator
|
|
// token, or return std::nullopt if the given token is not an infix or postfix
|
|
// operator. `infix` indicates whether this is a valid infix operator, but is
|
|
// only considered if the same operator symbol is available as both infix and
|
|
// postfix.
|
|
static auto ForTrailing(TokenKind kind, bool infix)
|
|
-> std::optional<Trailing>;
|
|
|
|
friend auto operator==(PrecedenceGroup lhs, PrecedenceGroup rhs) -> bool {
|
|
return lhs.level_ == rhs.level_;
|
|
}
|
|
friend auto operator!=(PrecedenceGroup lhs, PrecedenceGroup rhs) -> bool {
|
|
return lhs.level_ != rhs.level_;
|
|
}
|
|
|
|
// Compare the precedence levels for two adjacent operators.
|
|
static auto GetPriority(PrecedenceGroup left, PrecedenceGroup right)
|
|
-> OperatorPriority;
|
|
|
|
// Get the associativity of this precedence group.
|
|
[[nodiscard]] auto GetAssociativity() const -> Associativity {
|
|
return static_cast<Associativity>(GetPriority(*this, *this));
|
|
}
|
|
|
|
private:
|
|
// We rely on implicit conversions via `int8_t` for enumerators defined in the
|
|
// implementation.
|
|
// NOLINTNEXTLINE(google-explicit-constructor)
|
|
PrecedenceGroup(int8_t level) : level_(level) {}
|
|
|
|
// The precedence level.
|
|
int8_t level_;
|
|
};
|
|
|
|
// Precedence information for a trailing operator.
|
|
struct PrecedenceGroup::Trailing {
|
|
// The precedence level.
|
|
PrecedenceGroup level;
|
|
// `true` if this is an infix binary operator, `false` if this is a postfix
|
|
// unary operator.
|
|
bool is_binary;
|
|
};
|
|
|
|
} // namespace Carbon
|
|
|
|
#endif // CARBON_TOOLCHAIN_PARSER_PRECEDENCE_H_
|