bjoernager/rust
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Tighten up assignment operator representations.

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In the AST, currently we use `BinOpKind` within `ExprKind::AssignOp` and
`AssocOp::AssignOp`, even though this allows some nonsensical
combinations. E.g. there is no `&&=` operator. Likewise for HIR and
THIR.

This commit introduces `AssignOpKind` which only includes the ten
assignable operators, and uses it in `ExprKind::AssignOp` and
`AssocOp::AssignOp`. (And does similar things for `hir::ExprKind` and
`thir::ExprKind`.) This avoids the possibility of nonsensical
combinations, as seen by the removal of the `bug!` case in
`lang_item_for_binop`.

The commit is mostly plumbing, including:
- Adds an `impl From<AssignOpKind> for BinOpKind` (AST) and `impl
  From<AssignOp> for BinOp` (MIR/THIR).
- `BinOpCategory` can now be created from both `BinOpKind` and
  `AssignOpKind`.
- Replaces the `IsAssign` type with `Op`, which has more information and
  a few methods.
- `suggest_swapping_lhs_and_rhs`: moves the condition to the call site,
  it's easier that way.
- `check_expr_inner`: had to factor out some code into a separate
  method.

I'm on the fence about whether avoiding the nonsensical combinations is
worth the extra code.
This commit is contained in:
Nicholas Nethercote 2024-12-20 10:15:05 +11:00
parent ac8ccf09b4
commit ddcb370bc6
26 changed files with 391 additions and 239 deletions
Download patch file Download diff file Expand all files Collapse all files

14
compiler/rustc_parse/src/parser/expr.rs
View file

@ -14,10 +14,10 @@ use rustc_ast::util::classify;
use rustc_ast::util::parser::{AssocOp, ExprPrecedence, Fixity, prec_let_scrutinee_needs_par};
use rustc_ast::visit::{Visitor, walk_expr};
use rustc_ast::{
self as ast, AnonConst, Arm, AttrStyle, AttrVec, BinOp, BinOpKind, BlockCheckMode, CaptureBy,
ClosureBinder, DUMMY_NODE_ID, Expr, ExprField, ExprKind, FnDecl, FnRetTy, Label, MacCall,
MetaItemLit, Movability, Param, RangeLimits, StmtKind, Ty, TyKind, UnOp, UnsafeBinderCastKind,
YieldKind,
self as ast, AnonConst, Arm, AssignOp, AssignOpKind, AttrStyle, AttrVec, BinOp, BinOpKind,
BlockCheckMode, CaptureBy, ClosureBinder, DUMMY_NODE_ID, Expr, ExprField, ExprKind, FnDecl,
FnRetTy, Label, MacCall, MetaItemLit, Movability, Param, RangeLimits, StmtKind, Ty, TyKind,
UnOp, UnsafeBinderCastKind, YieldKind,
};
use rustc_data_structures::stack::ensure_sufficient_stack;
use rustc_errors::{Applicability, Diag, PResult, StashKey, Subdiagnostic};
@ -359,7 +359,7 @@ impl<'a> Parser<'a> {
(
Some(
AssocOp::Binary(BinOpKind::Shr | BinOpKind::Gt | BinOpKind::Ge)
| AssocOp::AssignOp(BinOpKind::Shr),
| AssocOp::AssignOp(AssignOpKind::ShrAssign),
),
_,
) if self.restrictions.contains(Restrictions::CONST_EXPR) => {
@ -3914,8 +3914,8 @@ impl<'a> Parser<'a> {
self.dcx().emit_err(errors::LeftArrowOperator { span });
}
fn mk_assign_op(&self, binop: BinOp, lhs: P<Expr>, rhs: P<Expr>) -> ExprKind {
ExprKind::AssignOp(binop, lhs, rhs)
fn mk_assign_op(&self, assign_op: AssignOp, lhs: P<Expr>, rhs: P<Expr>) -> ExprKind {
ExprKind::AssignOp(assign_op, lhs, rhs)
}
fn mk_range(