diff --git a/compiler/rustc_ast/src/ast.rs b/compiler/rustc_ast/src/ast.rs index 4360fbeb9bbc1..a398fd80119be 100644 --- a/compiler/rustc_ast/src/ast.rs +++ b/compiler/rustc_ast/src/ast.rs @@ -1295,6 +1295,7 @@ impl Expr { ExprKind::Yield(..) => ExprPrecedence::Yield, ExprKind::Yeet(..) => ExprPrecedence::Yeet, ExprKind::FormatArgs(..) => ExprPrecedence::FormatArgs, + ExprKind::Become(..) => ExprPrecedence::Become, ExprKind::Err => ExprPrecedence::Err, } } @@ -1515,6 +1516,11 @@ pub enum ExprKind { /// with an optional value to be returned. Yeet(Option>), + /// A tail call return, with the value to be returned. + /// + /// While `.0` must be a function call, we check this later, after parsing. + Become(P), + /// Bytes included via `include_bytes!` /// Added for optimization purposes to avoid the need to escape /// large binary blobs - should always behave like [`ExprKind::Lit`] diff --git a/compiler/rustc_ast/src/mut_visit.rs b/compiler/rustc_ast/src/mut_visit.rs index 66b94d12a32c6..53a9c9a046ea0 100644 --- a/compiler/rustc_ast/src/mut_visit.rs +++ b/compiler/rustc_ast/src/mut_visit.rs @@ -1457,6 +1457,7 @@ pub fn noop_visit_expr( ExprKind::Yeet(expr) => { visit_opt(expr, |expr| vis.visit_expr(expr)); } + ExprKind::Become(expr) => vis.visit_expr(expr), ExprKind::InlineAsm(asm) => vis.visit_inline_asm(asm), ExprKind::FormatArgs(fmt) => vis.visit_format_args(fmt), ExprKind::OffsetOf(container, fields) => { diff --git a/compiler/rustc_ast/src/util/parser.rs b/compiler/rustc_ast/src/util/parser.rs index 35afd5423721d..096077e09bf76 100644 --- a/compiler/rustc_ast/src/util/parser.rs +++ b/compiler/rustc_ast/src/util/parser.rs @@ -245,6 +245,7 @@ pub enum ExprPrecedence { Ret, Yield, Yeet, + Become, Range, @@ -298,7 +299,8 @@ impl ExprPrecedence { | ExprPrecedence::Continue | ExprPrecedence::Ret | ExprPrecedence::Yield - | ExprPrecedence::Yeet => PREC_JUMP, + | ExprPrecedence::Yeet + | ExprPrecedence::Become => PREC_JUMP, // `Range` claims to have higher precedence than `Assign`, but `x .. x = x` fails to // parse, instead of parsing as `(x .. x) = x`. Giving `Range` a lower precedence diff --git a/compiler/rustc_ast/src/visit.rs b/compiler/rustc_ast/src/visit.rs index 275692ad5dda7..d9de5b8e197db 100644 --- a/compiler/rustc_ast/src/visit.rs +++ b/compiler/rustc_ast/src/visit.rs @@ -908,6 +908,7 @@ pub fn walk_expr<'a, V: Visitor<'a>>(visitor: &mut V, expression: &'a Expr) { ExprKind::Yeet(optional_expression) => { walk_list!(visitor, visit_expr, optional_expression); } + ExprKind::Become(expr) => visitor.visit_expr(expr), ExprKind::MacCall(mac) => visitor.visit_mac_call(mac), ExprKind::Paren(subexpression) => visitor.visit_expr(subexpression), ExprKind::InlineAsm(asm) => visitor.visit_inline_asm(asm), diff --git a/compiler/rustc_ast_lowering/src/expr.rs b/compiler/rustc_ast_lowering/src/expr.rs index f52797c4f3f1d..225714a13615f 100644 --- a/compiler/rustc_ast_lowering/src/expr.rs +++ b/compiler/rustc_ast_lowering/src/expr.rs @@ -275,6 +275,12 @@ impl<'hir> LoweringContext<'_, 'hir> { hir::ExprKind::Ret(e) } ExprKind::Yeet(sub_expr) => self.lower_expr_yeet(e.span, sub_expr.as_deref()), + ExprKind::Become(sub_expr) => { + let sub_expr = self.lower_expr(sub_expr); + + // FIXME(explicit_tail_calls): Use `hir::ExprKind::Become` once we implemented it + hir::ExprKind::Ret(Some(sub_expr)) + } ExprKind::InlineAsm(asm) => { hir::ExprKind::InlineAsm(self.lower_inline_asm(e.span, asm)) } diff --git a/compiler/rustc_ast_passes/src/feature_gate.rs b/compiler/rustc_ast_passes/src/feature_gate.rs index 2125349909ef1..b0dbc2c23403e 100644 --- a/compiler/rustc_ast_passes/src/feature_gate.rs +++ b/compiler/rustc_ast_passes/src/feature_gate.rs @@ -555,6 +555,7 @@ pub fn check_crate(krate: &ast::Crate, sess: &Session) { gate_all!(dyn_star, "`dyn*` trait objects are experimental"); gate_all!(const_closures, "const closures are experimental"); gate_all!(builtin_syntax, "`builtin #` syntax is unstable"); + gate_all!(explicit_tail_calls, "`become` expression is experimental"); if !visitor.features.negative_bounds { for &span in spans.get(&sym::negative_bounds).iter().copied().flatten() { diff --git a/compiler/rustc_ast_pretty/src/pprust/state/expr.rs b/compiler/rustc_ast_pretty/src/pprust/state/expr.rs index 87c32ffce1214..609920180a2fa 100644 --- a/compiler/rustc_ast_pretty/src/pprust/state/expr.rs +++ b/compiler/rustc_ast_pretty/src/pprust/state/expr.rs @@ -537,6 +537,11 @@ impl<'a> State<'a> { self.print_expr_maybe_paren(expr, parser::PREC_JUMP); } } + ast::ExprKind::Become(result) => { + self.word("become"); + self.word(" "); + self.print_expr_maybe_paren(result, parser::PREC_JUMP); + } ast::ExprKind::InlineAsm(a) => { // FIXME: This should have its own syntax, distinct from a macro invocation. self.word("asm!"); diff --git a/compiler/rustc_builtin_macros/src/assert/context.rs b/compiler/rustc_builtin_macros/src/assert/context.rs index b619e80e15f3c..902c1e40c7541 100644 --- a/compiler/rustc_builtin_macros/src/assert/context.rs +++ b/compiler/rustc_builtin_macros/src/assert/context.rs @@ -320,6 +320,7 @@ impl<'cx, 'a> Context<'cx, 'a> { | ExprKind::Underscore | ExprKind::While(_, _, _) | ExprKind::Yeet(_) + | ExprKind::Become(_) | ExprKind::Yield(_) => {} } } diff --git a/compiler/rustc_feature/src/active.rs b/compiler/rustc_feature/src/active.rs index 4c53f9d8369fd..20a33e7fb36e3 100644 --- a/compiler/rustc_feature/src/active.rs +++ b/compiler/rustc_feature/src/active.rs @@ -395,6 +395,8 @@ declare_features! ( (active, exclusive_range_pattern, "1.11.0", Some(37854), None), /// Allows exhaustive pattern matching on types that contain uninhabited types. (active, exhaustive_patterns, "1.13.0", Some(51085), None), + /// Allows explicit tail calls via `become` expression. + (incomplete, explicit_tail_calls, "CURRENT_RUSTC_VERSION", Some(112788), None), /// Allows using `efiapi`, `sysv64` and `win64` as calling convention /// for functions with varargs. (active, extended_varargs_abi_support, "1.65.0", Some(100189), None), diff --git a/compiler/rustc_parse/src/parser/expr.rs b/compiler/rustc_parse/src/parser/expr.rs index f00bc54589a7f..88c6cc1ae7072 100644 --- a/compiler/rustc_parse/src/parser/expr.rs +++ b/compiler/rustc_parse/src/parser/expr.rs @@ -1430,6 +1430,8 @@ impl<'a> Parser<'a> { self.parse_expr_yield() } else if self.is_do_yeet() { self.parse_expr_yeet() + } else if self.eat_keyword(kw::Become) { + self.parse_expr_become() } else if self.check_keyword(kw::Let) { self.parse_expr_let() } else if self.eat_keyword(kw::Underscore) { @@ -1746,6 +1748,16 @@ impl<'a> Parser<'a> { self.maybe_recover_from_bad_qpath(expr) } + /// Parse `"become" expr`, with `"become"` token already eaten. + fn parse_expr_become(&mut self) -> PResult<'a, P> { + let lo = self.prev_token.span; + let kind = ExprKind::Become(self.parse_expr()?); + let span = lo.to(self.prev_token.span); + self.sess.gated_spans.gate(sym::explicit_tail_calls, span); + let expr = self.mk_expr(span, kind); + self.maybe_recover_from_bad_qpath(expr) + } + /// Parse `"break" (('label (:? expr)?) | expr?)` with `"break"` token already eaten. /// If the label is followed immediately by a `:` token, the label and `:` are /// parsed as part of the expression (i.e. a labeled loop). The language team has diff --git a/compiler/rustc_passes/src/hir_stats.rs b/compiler/rustc_passes/src/hir_stats.rs index dc5e454074ded..90809270118d0 100644 --- a/compiler/rustc_passes/src/hir_stats.rs +++ b/compiler/rustc_passes/src/hir_stats.rs @@ -569,7 +569,8 @@ impl<'v> ast_visit::Visitor<'v> for StatCollector<'v> { Array, ConstBlock, Call, MethodCall, Tup, Binary, Unary, Lit, Cast, Type, Let, If, While, ForLoop, Loop, Match, Closure, Block, Async, Await, TryBlock, Assign, AssignOp, Field, Index, Range, Underscore, Path, AddrOf, Break, Continue, Ret, - InlineAsm, FormatArgs, OffsetOf, MacCall, Struct, Repeat, Paren, Try, Yield, Yeet, IncludedBytes, Err + InlineAsm, FormatArgs, OffsetOf, MacCall, Struct, Repeat, Paren, Try, Yield, Yeet, + Become, IncludedBytes, Err ] ); ast_visit::walk_expr(self, e) diff --git a/compiler/rustc_span/src/symbol.rs b/compiler/rustc_span/src/symbol.rs index bd39cbf17cec1..3282a82d9774b 100644 --- a/compiler/rustc_span/src/symbol.rs +++ b/compiler/rustc_span/src/symbol.rs @@ -686,6 +686,7 @@ symbols! { expf32, expf64, explicit_generic_args_with_impl_trait, + explicit_tail_calls, export_name, expr, extended_key_value_attributes, diff --git a/src/tools/clippy/clippy_utils/src/sugg.rs b/src/tools/clippy/clippy_utils/src/sugg.rs index f477524eec5cc..a87d58110b0c1 100644 --- a/src/tools/clippy/clippy_utils/src/sugg.rs +++ b/src/tools/clippy/clippy_utils/src/sugg.rs @@ -211,6 +211,7 @@ impl<'a> Sugg<'a> { | ast::ExprKind::Path(..) | ast::ExprKind::Repeat(..) | ast::ExprKind::Ret(..) + | ast::ExprKind::Become(..) | ast::ExprKind::Yeet(..) | ast::ExprKind::FormatArgs(..) | ast::ExprKind::Struct(..) diff --git a/src/tools/rustfmt/src/expr.rs b/src/tools/rustfmt/src/expr.rs index 5dc628adb0c6f..44aaddd8cb27f 100644 --- a/src/tools/rustfmt/src/expr.rs +++ b/src/tools/rustfmt/src/expr.rs @@ -232,6 +232,7 @@ pub(crate) fn format_expr( ast::ExprKind::Ret(Some(ref expr)) => { rewrite_unary_prefix(context, "return ", &**expr, shape) } + ast::ExprKind::Become(ref expr) => rewrite_unary_prefix(context, "become ", &**expr, shape), ast::ExprKind::Yeet(None) => Some("do yeet".to_owned()), ast::ExprKind::Yeet(Some(ref expr)) => { rewrite_unary_prefix(context, "do yeet ", &**expr, shape) diff --git a/src/tools/rustfmt/src/utils.rs b/src/tools/rustfmt/src/utils.rs index ca1716574071b..890a05b8c8259 100644 --- a/src/tools/rustfmt/src/utils.rs +++ b/src/tools/rustfmt/src/utils.rs @@ -505,6 +505,7 @@ pub(crate) fn is_block_expr(context: &RewriteContext<'_>, expr: &ast::Expr, repr | ast::ExprKind::Range(..) | ast::ExprKind::Repeat(..) | ast::ExprKind::Ret(..) + | ast::ExprKind::Become(..) | ast::ExprKind::Yeet(..) | ast::ExprKind::Tup(..) | ast::ExprKind::Type(..) diff --git a/tests/ui/feature-gates/feature-gate-explicit_tail_calls.rs b/tests/ui/feature-gates/feature-gate-explicit_tail_calls.rs new file mode 100644 index 0000000000000..856a7f393289a --- /dev/null +++ b/tests/ui/feature-gates/feature-gate-explicit_tail_calls.rs @@ -0,0 +1,9 @@ +pub fn you() -> T { + become bottom(); //~ error: `become` expression is experimental +} + +pub fn bottom() -> T { + become you(); //~ error: `become` expression is experimental +} + +fn main() {} diff --git a/tests/ui/feature-gates/feature-gate-explicit_tail_calls.stderr b/tests/ui/feature-gates/feature-gate-explicit_tail_calls.stderr new file mode 100644 index 0000000000000..b58da19c1745f --- /dev/null +++ b/tests/ui/feature-gates/feature-gate-explicit_tail_calls.stderr @@ -0,0 +1,21 @@ +error[E0658]: `become` expression is experimental + --> $DIR/feature-gate-explicit_tail_calls.rs:2:5 + | +LL | become bottom(); + | ^^^^^^^^^^^^^^^ + | + = note: see issue #112788 for more information + = help: add `#![feature(explicit_tail_calls)]` to the crate attributes to enable + +error[E0658]: `become` expression is experimental + --> $DIR/feature-gate-explicit_tail_calls.rs:6:5 + | +LL | become you(); + | ^^^^^^^^^^^^ + | + = note: see issue #112788 for more information + = help: add `#![feature(explicit_tail_calls)]` to the crate attributes to enable + +error: aborting due to 2 previous errors + +For more information about this error, try `rustc --explain E0658`.