ExprKind::Range(ref e1, ref e2, lims) => {
self.lower_expr_range(e.span, e1.as_deref(), e2.as_deref(), lims)
}
+ ExprKind::Underscore => {
+ self.sess
+ .struct_span_err(
+ e.span,
+ "in expressions, `_` can only be used on the left-hand side of an assignment",
+ )
+ .span_label(e.span, "`_` not allowed here")
+ .emit();
+ hir::ExprKind::Err
+ }
ExprKind::Path(ref qself, ref path) => {
let qpath = self.lower_qpath(
e.id,
}
ExprKind::InlineAsm(ref asm) => self.lower_expr_asm(e.span, asm),
ExprKind::LlvmInlineAsm(ref asm) => self.lower_expr_llvm_asm(asm),
- ExprKind::Struct(ref path, ref fields, ref maybe_expr) => {
- let maybe_expr = maybe_expr.as_ref().map(|x| self.lower_expr(x));
+ ExprKind::Struct(ref path, ref fields, ref rest) => {
+ let rest = match rest {
+ StructRest::Base(e) => Some(self.lower_expr(e)),
+ StructRest::Rest(sp) => {
+ self.sess
+ .struct_span_err(*sp, "base expression required after `..`")
+ .span_label(*sp, "add a base expression here")
+ .emit();
+ Some(&*self.arena.alloc(self.expr_err(*sp)))
+ }
+ StructRest::None => None,
+ };
hir::ExprKind::Struct(
self.arena.alloc(self.lower_qpath(
e.id,
ImplTraitContext::disallowed(),
)),
self.arena.alloc_from_iter(fields.iter().map(|x| self.lower_field(x))),
- maybe_expr,
+ rest,
)
}
ExprKind::Yield(ref opt_expr) => self.lower_expr_yield(e.span, opt_expr.as_deref()),
whole_span: Span,
) -> hir::ExprKind<'hir> {
// Return early in case of an ordinary assignment.
- fn is_ordinary(lhs: &Expr) -> bool {
+ fn is_ordinary(lower_ctx: &mut LoweringContext<'_, '_>, lhs: &Expr) -> bool {
match &lhs.kind {
- ExprKind::Tup(..) => false,
+ ExprKind::Array(..)
+ | ExprKind::Struct(..)
+ | ExprKind::Tup(..)
+ | ExprKind::Underscore => false,
+ // Check for tuple struct constructor.
+ ExprKind::Call(callee, ..) => lower_ctx.extract_tuple_struct_path(callee).is_none(),
ExprKind::Paren(e) => {
match e.kind {
// We special-case `(..)` for consistency with patterns.
ExprKind::Range(None, None, RangeLimits::HalfOpen) => false,
- _ => is_ordinary(e),
+ _ => is_ordinary(lower_ctx, e),
}
}
_ => true,
}
}
- if is_ordinary(lhs) {
+ if is_ordinary(self, lhs) {
return hir::ExprKind::Assign(self.lower_expr(lhs), self.lower_expr(rhs), eq_sign_span);
}
if !self.sess.features_untracked().destructuring_assignment {
hir::ExprKind::Block(&self.block_all(whole_span, stmts, None), None)
}
+ /// If the given expression is a path to a tuple struct, returns that path.
+ /// It is not a complete check, but just tries to reject most paths early
+ /// if they are not tuple structs.
+ /// Type checking will take care of the full validation later.
+ fn extract_tuple_struct_path<'a>(&mut self, expr: &'a Expr) -> Option<&'a Path> {
+ // For tuple struct destructuring, it must be a non-qualified path (like in patterns).
+ if let ExprKind::Path(None, path) = &expr.kind {
+ // Does the path resolves to something disallowed in a tuple struct/variant pattern?
+ if let Some(partial_res) = self.resolver.get_partial_res(expr.id) {
+ if partial_res.unresolved_segments() == 0
+ && !partial_res.base_res().expected_in_tuple_struct_pat()
+ {
+ return None;
+ }
+ }
+ return Some(path);
+ }
+ None
+ }
+
/// Convert the LHS of a destructuring assignment to a pattern.
/// Each sub-assignment is recorded in `assignments`.
fn destructure_assign(
assignments: &mut Vec<hir::Stmt<'hir>>,
) -> &'hir hir::Pat<'hir> {
match &lhs.kind {
+ // Underscore pattern.
+ ExprKind::Underscore => {
+ return self.pat_without_dbm(lhs.span, hir::PatKind::Wild);
+ }
+ // Slice patterns.
+ ExprKind::Array(elements) => {
+ let (pats, rest) =
+ self.destructure_sequence(elements, "slice", eq_sign_span, assignments);
+ let slice_pat = if let Some((i, span)) = rest {
+ let (before, after) = pats.split_at(i);
+ hir::PatKind::Slice(
+ before,
+ Some(self.pat_without_dbm(span, hir::PatKind::Wild)),
+ after,
+ )
+ } else {
+ hir::PatKind::Slice(pats, None, &[])
+ };
+ return self.pat_without_dbm(lhs.span, slice_pat);
+ }
+ // Tuple structs.
+ ExprKind::Call(callee, args) => {
+ if let Some(path) = self.extract_tuple_struct_path(callee) {
+ let (pats, rest) = self.destructure_sequence(
+ args,
+ "tuple struct or variant",
+ eq_sign_span,
+ assignments,
+ );
+ let qpath = self.lower_qpath(
+ callee.id,
+ &None,
+ path,
+ ParamMode::Optional,
+ ImplTraitContext::disallowed(),
+ );
+ // Destructure like a tuple struct.
+ let tuple_struct_pat =
+ hir::PatKind::TupleStruct(qpath, pats, rest.map(|r| r.0));
+ return self.pat_without_dbm(lhs.span, tuple_struct_pat);
+ }
+ }
+ // Structs.
+ ExprKind::Struct(path, fields, rest) => {
+ let field_pats = self.arena.alloc_from_iter(fields.iter().map(|f| {
+ let pat = self.destructure_assign(&f.expr, eq_sign_span, assignments);
+ hir::FieldPat {
+ hir_id: self.next_id(),
+ ident: f.ident,
+ pat,
+ is_shorthand: f.is_shorthand,
+ span: f.span,
+ }
+ }));
+ let qpath = self.lower_qpath(
+ lhs.id,
+ &None,
+ path,
+ ParamMode::Optional,
+ ImplTraitContext::disallowed(),
+ );
+ let fields_omitted = match rest {
+ StructRest::Base(e) => {
+ self.sess
+ .struct_span_err(
+ e.span,
+ "functional record updates are not allowed in destructuring \
+ assignments",
+ )
+ .span_suggestion(
+ e.span,
+ "consider removing the trailing pattern",
+ String::new(),
+ rustc_errors::Applicability::MachineApplicable,
+ )
+ .emit();
+ true
+ }
+ StructRest::Rest(_) => true,
+ StructRest::None => false,
+ };
+ let struct_pat = hir::PatKind::Struct(qpath, field_pats, fields_omitted);
+ return self.pat_without_dbm(lhs.span, struct_pat);
+ }
// Tuples.
ExprKind::Tup(elements) => {
let (pats, rest) =
projects / rust.git / blobdiff