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|
use rustc_span::kw;
use crate::ast::{self, BinOpKind, RangeLimits};
use crate::token::{self, Token};
/// Associative operator.
#[derive(Copy, Clone, PartialEq, Debug)]
pub enum AssocOp {
/// A binary op.
Binary(BinOpKind),
/// `?=` where ? is one of the assignable BinOps
AssignOp(BinOpKind),
/// `=`
Assign,
/// `as`
Cast,
/// `..` or `..=` range
Range(RangeLimits),
}
#[derive(PartialEq, Debug)]
pub enum Fixity {
/// The operator is left-associative
Left,
/// The operator is right-associative
Right,
/// The operator is not associative
None,
}
impl AssocOp {
/// Creates a new AssocOp from a token.
pub fn from_token(t: &Token) -> Option<AssocOp> {
use AssocOp::*;
match t.kind {
token::Eq => Some(Assign),
token::Plus => Some(Binary(BinOpKind::Add)),
token::Minus => Some(Binary(BinOpKind::Sub)),
token::Star => Some(Binary(BinOpKind::Mul)),
token::Slash => Some(Binary(BinOpKind::Div)),
token::Percent => Some(Binary(BinOpKind::Rem)),
token::Caret => Some(Binary(BinOpKind::BitXor)),
token::And => Some(Binary(BinOpKind::BitAnd)),
token::Or => Some(Binary(BinOpKind::BitOr)),
token::Shl => Some(Binary(BinOpKind::Shl)),
token::Shr => Some(Binary(BinOpKind::Shr)),
token::PlusEq => Some(AssignOp(BinOpKind::Add)),
token::MinusEq => Some(AssignOp(BinOpKind::Sub)),
token::StarEq => Some(AssignOp(BinOpKind::Mul)),
token::SlashEq => Some(AssignOp(BinOpKind::Div)),
token::PercentEq => Some(AssignOp(BinOpKind::Rem)),
token::CaretEq => Some(AssignOp(BinOpKind::BitXor)),
token::AndEq => Some(AssignOp(BinOpKind::BitAnd)),
token::OrEq => Some(AssignOp(BinOpKind::BitOr)),
token::ShlEq => Some(AssignOp(BinOpKind::Shl)),
token::ShrEq => Some(AssignOp(BinOpKind::Shr)),
token::Lt => Some(Binary(BinOpKind::Lt)),
token::Le => Some(Binary(BinOpKind::Le)),
token::Ge => Some(Binary(BinOpKind::Ge)),
token::Gt => Some(Binary(BinOpKind::Gt)),
token::EqEq => Some(Binary(BinOpKind::Eq)),
token::Ne => Some(Binary(BinOpKind::Ne)),
token::AndAnd => Some(Binary(BinOpKind::And)),
token::OrOr => Some(Binary(BinOpKind::Or)),
token::DotDot => Some(Range(RangeLimits::HalfOpen)),
// DotDotDot is no longer supported, but we need some way to display the error
token::DotDotEq | token::DotDotDot => Some(Range(RangeLimits::Closed)),
// `<-` should probably be `< -`
token::LArrow => Some(Binary(BinOpKind::Lt)),
_ if t.is_keyword(kw::As) => Some(Cast),
_ => None,
}
}
/// Gets the precedence of this operator
pub fn precedence(&self) -> ExprPrecedence {
use AssocOp::*;
match *self {
Cast => ExprPrecedence::Cast,
Binary(bin_op) => bin_op.precedence(),
Range(_) => ExprPrecedence::Range,
Assign | AssignOp(_) => ExprPrecedence::Assign,
}
}
/// Gets the fixity of this operator
pub fn fixity(&self) -> Fixity {
use AssocOp::*;
// NOTE: it is a bug to have an operators that has same precedence but different fixities!
match *self {
Assign | AssignOp(_) => Fixity::Right,
Binary(binop) => binop.fixity(),
Cast => Fixity::Left,
Range(_) => Fixity::None,
}
}
pub fn is_comparison(&self) -> bool {
use AssocOp::*;
match *self {
Binary(binop) => binop.is_comparison(),
Assign | AssignOp(_) | Cast | Range(_) => false,
}
}
pub fn is_assign_like(&self) -> bool {
use AssocOp::*;
match *self {
Assign | AssignOp(_) => true,
Cast | Binary(_) | Range(_) => false,
}
}
/// This operator could be used to follow a block unambiguously.
///
/// This is used for error recovery at the moment, providing a suggestion to wrap blocks with
/// parentheses while having a high degree of confidence on the correctness of the suggestion.
pub fn can_continue_expr_unambiguously(&self) -> bool {
use AssocOp::*;
use BinOpKind::*;
matches!(
self,
Assign | // `{ 42 } = { 42 }`
Binary(
BitXor | // `{ 42 } ^ 3`
Div | // `{ 42 } / 42`
Rem | // `{ 42 } % 2`
Shr | // `{ 42 } >> 2`
Le | // `{ 42 } <= 3`
Gt | // `{ 42 } > 3`
Ge // `{ 42 } >= 3`
) |
AssignOp(_) | // `{ 42 } +=`
// Equal | // `{ 42 } == { 42 }` Accepting these here would regress incorrect
// NotEqual | // `{ 42 } != { 42 } struct literals parser recovery.
Cast // `{ 42 } as usize`
)
}
}
#[derive(Clone, Copy, PartialEq, PartialOrd)]
pub enum ExprPrecedence {
// return, break, yield, closures
Jump,
// = += -= *= /= %= &= |= ^= <<= >>=
Assign,
// .. ..=
Range,
// ||
LOr,
// &&
LAnd,
// == != < > <= >=
Compare,
// |
BitOr,
// ^
BitXor,
// &
BitAnd,
// << >>
Shift,
// + -
Sum,
// * / %
Product,
// as
Cast,
// unary - * ! & &mut
Prefix,
// paths, loops, function calls, array indexing, field expressions, method calls
Unambiguous,
}
/// In `let p = e`, operators with precedence `<=` this one requires parentheses in `e`.
pub fn prec_let_scrutinee_needs_par() -> ExprPrecedence {
ExprPrecedence::LAnd
}
/// Suppose we have `let _ = e` and the `order` of `e`.
/// Is the `order` such that `e` in `let _ = e` needs parentheses when it is on the RHS?
///
/// Conversely, suppose that we have `(let _ = a) OP b` and `order` is that of `OP`.
/// Can we print this as `let _ = a OP b`?
pub fn needs_par_as_let_scrutinee(order: ExprPrecedence) -> bool {
order <= prec_let_scrutinee_needs_par()
}
/// Expressions that syntactically contain an "exterior" struct literal i.e., not surrounded by any
/// parens or other delimiters, e.g., `X { y: 1 }`, `X { y: 1 }.method()`, `foo == X { y: 1 }` and
/// `X { y: 1 } == foo` all do, but `(X { y: 1 }) == foo` does not.
pub fn contains_exterior_struct_lit(value: &ast::Expr) -> bool {
match &value.kind {
ast::ExprKind::Struct(..) => true,
ast::ExprKind::Assign(lhs, rhs, _)
| ast::ExprKind::AssignOp(_, lhs, rhs)
| ast::ExprKind::Binary(_, lhs, rhs) => {
// X { y: 1 } + X { y: 2 }
contains_exterior_struct_lit(lhs) || contains_exterior_struct_lit(rhs)
}
ast::ExprKind::Await(x, _)
| ast::ExprKind::Unary(_, x)
| ast::ExprKind::Cast(x, _)
| ast::ExprKind::Type(x, _)
| ast::ExprKind::Field(x, _)
| ast::ExprKind::Index(x, _, _)
| ast::ExprKind::Match(x, _, ast::MatchKind::Postfix) => {
// &X { y: 1 }, X { y: 1 }.y
contains_exterior_struct_lit(x)
}
ast::ExprKind::MethodCall(box ast::MethodCall { receiver, .. }) => {
// X { y: 1 }.bar(...)
contains_exterior_struct_lit(receiver)
}
_ => false,
}
}
|
