Plumb awaitness of for loops

eholk · eholk · commit caa63dc8158c · 2023-12-08T14:51:50.000-08:00
diff --git a/compiler/rustc_ast/src/ast.rs b/compiler/rustc_ast/src/ast.rs
@@ -1261,7 +1261,7 @@ impl Expr {
             ExprKind::Let(..) => ExprPrecedence::Let,
             ExprKind::If(..) => ExprPrecedence::If,
             ExprKind::While(..) => ExprPrecedence::While,
-            ExprKind::ForLoop(..) => ExprPrecedence::ForLoop,
+            ExprKind::ForLoop { .. } => ExprPrecedence::ForLoop,
             ExprKind::Loop(..) => ExprPrecedence::Loop,
             ExprKind::Match(..) => ExprPrecedence::Match,
             ExprKind::Closure(..) => ExprPrecedence::Closure,
@@ -1423,10 +1423,10 @@ pub enum ExprKind {
     While(P<Expr>, P<Block>, Option<Label>),
     /// A `for` loop, with an optional label.
     ///
-    /// `'label: for pat in expr { block }`
+    /// `'label: for await? pat in iter { block }`
     ///
     /// This is desugared to a combination of `loop` and `match` expressions.
-    ForLoop(P<Pat>, P<Expr>, P<Block>, Option<Label>),
+    ForLoop { pat: P<Pat>, iter: P<Expr>, body: P<Block>, label: Option<Label>, is_await: bool },
     /// Conditionless loop (can be exited with `break`, `continue`, or `return`).
     ///
     /// `'label: loop { block }`
diff --git a/compiler/rustc_ast/src/mut_visit.rs b/compiler/rustc_ast/src/mut_visit.rs
@@ -1388,7 +1388,7 @@ pub fn noop_visit_expr<T: MutVisitor>(
             vis.visit_block(body);
             visit_opt(label, |label| vis.visit_label(label));
         }
-        ExprKind::ForLoop(pat, iter, body, label) => {
+        ExprKind::ForLoop{pat, iter, body, label, is_await: _} => {
             vis.visit_pat(pat);
             vis.visit_expr(iter);
             vis.visit_block(body);
diff --git a/compiler/rustc_ast/src/util/classify.rs b/compiler/rustc_ast/src/util/classify.rs
@@ -19,7 +19,7 @@ pub fn expr_requires_semi_to_be_stmt(e: &ast::Expr) -> bool {
             | ast::ExprKind::Block(..)
             | ast::ExprKind::While(..)
             | ast::ExprKind::Loop(..)
-            | ast::ExprKind::ForLoop(..)
+            | ast::ExprKind::ForLoop { .. }
             | ast::ExprKind::TryBlock(..)
             | ast::ExprKind::ConstBlock(..)
     )
@@ -46,8 +46,15 @@ pub fn expr_trailing_brace(mut expr: &ast::Expr) -> Option<&ast::Expr> {
             Closure(closure) => {
                 expr = &closure.body;
             }
-            Gen(..) | Block(..) | ForLoop(..) | If(..) | Loop(..) | Match(..) | Struct(..)
-            | TryBlock(..) | While(..) => break Some(expr),
+            Gen(..)
+            | Block(..)
+            | ForLoop { .. }
+            | If(..)
+            | Loop(..)
+            | Match(..)
+            | Struct(..)
+            | TryBlock(..)
+            | While(..) => break Some(expr),
             _ => break None,
         }
     }
diff --git a/compiler/rustc_ast/src/visit.rs b/compiler/rustc_ast/src/visit.rs
@@ -844,11 +844,11 @@ pub fn walk_expr<'a, V: Visitor<'a>>(visitor: &mut V, expression: &'a Expr) {
             visitor.visit_expr(subexpression);
             visitor.visit_block(block);
         }
-        ExprKind::ForLoop(pattern, subexpression, block, opt_label) => {
-            walk_list!(visitor, visit_label, opt_label);
-            visitor.visit_pat(pattern);
-            visitor.visit_expr(subexpression);
-            visitor.visit_block(block);
+        ExprKind::ForLoop { pat, iter, body, label, is_await: _ } => {
+            walk_list!(visitor, visit_label, label);
+            visitor.visit_pat(pat);
+            visitor.visit_expr(iter);
+            visitor.visit_block(body);
         }
         ExprKind::Loop(block, opt_label, _) => {
             walk_list!(visitor, visit_label, opt_label);
diff --git a/compiler/rustc_ast_lowering/src/expr.rs b/compiler/rustc_ast_lowering/src/expr.rs
@@ -56,12 +56,12 @@ impl<'hir> LoweringContext<'_, 'hir> {
                     return ex;
                 }
                 // Desugar `ExprForLoop`
-                // from: `[opt_ident]: for <pat> in <head> <body>`
+                // from: `[opt_ident]: for await? <pat> in <iter> <body>`
                 //
                 // This also needs special handling because the HirId of the returned `hir::Expr` will not
-                // correspond to the `e.id`, so `lower_expr_for` handles attribute lowering itself.
-                ExprKind::ForLoop(pat, head, body, opt_label) => {
-                    return self.lower_expr_for(e, pat, head, body, *opt_label);
+                // correspond to the `e.id`, so `lower_expr_for` handles attribute low}ering itself.
+                ExprKind::ForLoop { pat, iter, body, label, is_await } => {
+                    return self.lower_expr_for(e, pat, iter, body, *label, *is_await);
                 }
                 _ => (),
             }
@@ -331,7 +331,7 @@ impl<'hir> LoweringContext<'_, 'hir> {
                 ),
                 ExprKind::Try(sub_expr) => self.lower_expr_try(e.span, sub_expr),
 
-                ExprKind::Paren(_) | ExprKind::ForLoop(..) => {
+                ExprKind::Paren(_) | ExprKind::ForLoop{..} => {
                     unreachable!("already handled")
                 }
 
@@ -1554,6 +1554,7 @@ impl<'hir> LoweringContext<'_, 'hir> {
         head: &Expr,
         body: &Block,
         opt_label: Option<Label>,
+        _is_await: bool,
     ) -> hir::Expr<'hir> {
         let head = self.lower_expr_mut(head);
         let pat = self.lower_pat(pat);
diff --git a/compiler/rustc_ast_pretty/src/pprust/state/expr.rs b/compiler/rustc_ast_pretty/src/pprust/state/expr.rs
@@ -370,20 +370,23 @@ impl<'a> State<'a> {
                 self.space();
                 self.print_block_with_attrs(blk, attrs);
             }
-            ast::ExprKind::ForLoop(pat, iter, blk, opt_label) => {
-                if let Some(label) = opt_label {
+            ast::ExprKind::ForLoop { pat, iter, body, label, is_await } => {
+                if let Some(label) = label {
                     self.print_ident(label.ident);
                     self.word_space(":");
                 }
                 self.cbox(0);
                 self.ibox(0);
                 self.word_nbsp("for");
+                if *is_await {
+                    self.word_nbsp("await");
+                }
                 self.print_pat(pat);
                 self.space();
                 self.word_space("in");
                 self.print_expr_as_cond(iter);
                 self.space();
-                self.print_block_with_attrs(blk, attrs);
+                self.print_block_with_attrs(body, attrs);
             }
             ast::ExprKind::Loop(blk, opt_label, _) => {
                 if let Some(label) = opt_label {
diff --git a/compiler/rustc_builtin_macros/src/assert/context.rs b/compiler/rustc_builtin_macros/src/assert/context.rs
@@ -303,7 +303,7 @@ impl<'cx, 'a> Context<'cx, 'a> {
             | ExprKind::Continue(_)
             | ExprKind::Err
             | ExprKind::Field(_, _)
-            | ExprKind::ForLoop(_, _, _, _)
+            | ExprKind::ForLoop {..}
             | ExprKind::FormatArgs(_)
             | ExprKind::IncludedBytes(..)
             | ExprKind::InlineAsm(_)
diff --git a/compiler/rustc_lint/src/unused.rs b/compiler/rustc_lint/src/unused.rs
@@ -852,8 +852,8 @@ trait UnusedDelimLint {
                 (cond, UnusedDelimsCtx::WhileCond, true, Some(left), Some(right), true)
             }
 
-            ForLoop(_, ref cond, ref block, ..) => {
-                (cond, UnusedDelimsCtx::ForIterExpr, true, None, Some(block.span.lo()), true)
+            ForLoop { ref iter, ref body, .. } => {
+                (iter, UnusedDelimsCtx::ForIterExpr, true, None, Some(body.span.lo()), true)
             }
 
             Match(ref head, _) if Self::LINT_EXPR_IN_PATTERN_MATCHING_CTX => {
@@ -1085,7 +1085,7 @@ impl EarlyLintPass for UnusedParens {
         }
 
         match e.kind {
-            ExprKind::Let(ref pat, _, _, _) | ExprKind::ForLoop(ref pat, ..) => {
+            ExprKind::Let(ref pat, _, _, _) | ExprKind::ForLoop { ref pat, .. } => {
                 self.check_unused_parens_pat(cx, pat, false, false, (true, true));
             }
             // We ignore parens in cases like `if (((let Some(0) = Some(1))))` because we already
diff --git a/compiler/rustc_parse/src/parser/expr.rs b/compiler/rustc_parse/src/parser/expr.rs
@@ -1799,7 +1799,7 @@ impl<'a> Parser<'a> {
                     && matches!(
                         expr.kind,
                         ExprKind::While(_, _, None)
-                            | ExprKind::ForLoop(_, _, _, None)
+                            | ExprKind::ForLoop { label: None, .. }
                             | ExprKind::Loop(_, None, _)
                             | ExprKind::Block(_, None)
                     )
@@ -2672,8 +2672,14 @@ impl<'a> Parser<'a> {
         Ok((pat, expr))
     }
 
-    /// Parses `for <src_pat> in <src_expr> <src_loop_block>` (`for` token already eaten).
+    /// Parses `for await? <src_pat> in <src_expr> <src_loop_block>` (`for` token already eaten).
     fn parse_expr_for(&mut self, opt_label: Option<Label>, lo: Span) -> PResult<'a, P<Expr>> {
+        let is_await = self.eat_keyword(kw::Await);
+
+        if is_await {
+            self.sess.gated_spans.gate(sym::async_iterator, self.prev_token.span);
+        }
+
         let (pat, expr) = self.parse_for_head()?;
         // Recover from missing expression in `for` loop
         if matches!(expr.kind, ExprKind::Block(..))
@@ -2686,13 +2692,14 @@ impl<'a> Parser<'a> {
             let block = self.mk_block(thin_vec![], BlockCheckMode::Default, self.prev_token.span);
             return Ok(self.mk_expr(
                 lo.to(self.prev_token.span),
-                ExprKind::ForLoop(pat, err_expr, block, opt_label),
+                ExprKind::ForLoop { pat, iter: err_expr, body: block, label: opt_label, is_await },
             ));
         }
 
         let (attrs, loop_block) = self.parse_inner_attrs_and_block()?;
 
-        let kind = ExprKind::ForLoop(pat, expr, loop_block, opt_label);
+        let kind =
+            ExprKind::ForLoop { pat, iter: expr, body: loop_block, label: opt_label, is_await };
 
         self.recover_loop_else("for", lo)?;
 
@@ -3770,7 +3777,7 @@ impl MutVisitor for CondChecker<'_> {
             | ExprKind::Lit(_)
             | ExprKind::If(_, _, _)
             | ExprKind::While(_, _, _)
-            | ExprKind::ForLoop(_, _, _, _)
+            | ExprKind::ForLoop { .. }
             | ExprKind::Loop(_, _, _)
             | ExprKind::Match(_, _)
             | ExprKind::Closure(_)
diff --git a/compiler/rustc_resolve/src/late.rs b/compiler/rustc_resolve/src/late.rs
@@ -4246,11 +4246,11 @@ impl<'a: 'ast, 'b, 'ast, 'tcx> LateResolutionVisitor<'a, 'b, 'ast, 'tcx> {
                 });
             }
 
-            ExprKind::ForLoop(ref pat, ref iter_expr, ref block, label) => {
-                self.visit_expr(iter_expr);
+            ExprKind::ForLoop { ref pat, ref iter, ref body, label, is_await: _ } => {
+                self.visit_expr(iter);
                 self.with_rib(ValueNS, RibKind::Normal, |this| {
                     this.resolve_pattern_top(pat, PatternSource::For);
-                    this.resolve_labeled_block(label, expr.id, block);
+                    this.resolve_labeled_block(label, expr.id, body);
                 });
             }
 
diff --git a/compiler/rustc_resolve/src/late/diagnostics.rs b/compiler/rustc_resolve/src/late/diagnostics.rs
@@ -1409,7 +1409,7 @@ impl<'a: 'ast, 'ast, 'tcx> LateResolutionVisitor<'a, '_, 'ast, 'tcx> {
                             | ExprKind::Unary(..)
                             | ExprKind::If(..)
                             | ExprKind::While(..)
-                            | ExprKind::ForLoop(..)
+                            | ExprKind::ForLoop { .. }
                             | ExprKind::Match(..),
                         ..
                     }),
diff --git a/compiler/rustc_span/src/symbol.rs b/compiler/rustc_span/src/symbol.rs
@@ -423,6 +423,7 @@ symbols! {
         async_closure,
         async_fn_in_trait,
         async_fn_track_caller,
+        async_iterator,
         atomic,
         atomic_mod,
         atomics,
diff --git a/src/tools/clippy/clippy_lints/src/needless_continue.rs b/src/tools/clippy/clippy_lints/src/needless_continue.rs
@@ -220,7 +220,11 @@ where
     F: FnMut(&ast::Block, Option<&ast::Label>),
 {
     if let ast::ExprKind::While(_, loop_block, label)
-    | ast::ExprKind::ForLoop(_, _, loop_block, label)
+    | ast::ExprKind::ForLoop {
+        body: loop_block,
+        label,
+        ..
+    }
     | ast::ExprKind::Loop(loop_block, label, ..) = &expr.kind
     {
         func(loop_block, label.as_ref());
diff --git a/src/tools/clippy/clippy_lints/src/redundant_else.rs b/src/tools/clippy/clippy_lints/src/redundant_else.rs
@@ -111,7 +111,7 @@ impl<'ast> Visitor<'ast> for BreakVisitor {
             ExprKind::If(_, ref then, Some(ref els)) => self.check_block(then) && self.check_expr(els),
             ExprKind::If(_, _, None)
             // ignore loops for simplicity
-            | ExprKind::While(..) | ExprKind::ForLoop(..) | ExprKind::Loop(..) => false,
+            | ExprKind::While(..) | ExprKind::ForLoop { .. } | ExprKind::Loop(..) => false,
             _ => {
                 walk_expr(self, expr);
                 return;
diff --git a/src/tools/clippy/clippy_lints/src/suspicious_operation_groupings.rs b/src/tools/clippy/clippy_lints/src/suspicious_operation_groupings.rs
@@ -554,7 +554,7 @@ fn ident_difference_expr_with_base_location(
         | (Closure(_), Closure(_))
         | (Match(_, _), Match(_, _))
         | (Loop(_, _, _), Loop(_, _, _))
-        | (ForLoop(_, _, _, _), ForLoop(_, _, _, _))
+        | (ForLoop { .. }, ForLoop { .. })
         | (While(_, _, _), While(_, _, _))
         | (If(_, _, _), If(_, _, _))
         | (Let(_, _, _, _), Let(_, _, _, _))
diff --git a/src/tools/clippy/clippy_utils/src/ast_utils.rs b/src/tools/clippy/clippy_utils/src/ast_utils.rs
@@ -169,9 +169,22 @@ pub fn eq_expr(l: &Expr, r: &Expr) -> bool {
         (Let(lp, le, _, _), Let(rp, re, _, _)) => eq_pat(lp, rp) && eq_expr(le, re),
         (If(lc, lt, le), If(rc, rt, re)) => eq_expr(lc, rc) && eq_block(lt, rt) && eq_expr_opt(le, re),
         (While(lc, lt, ll), While(rc, rt, rl)) => eq_label(ll, rl) && eq_expr(lc, rc) && eq_block(lt, rt),
-        (ForLoop(lp, li, lt, ll), ForLoop(rp, ri, rt, rl)) => {
-            eq_label(ll, rl) && eq_pat(lp, rp) && eq_expr(li, ri) && eq_block(lt, rt)
-        },
+        (
+            ForLoop {
+                pat: lp,
+                iter: li,
+                body: lt,
+                label: ll,
+                is_await: la,
+            },
+            ForLoop {
+                pat: rp,
+                iter: ri,
+                body: rt,
+                label: rl,
+                is_await: ra,
+            },
+        ) => eq_label(ll, rl) && eq_pat(lp, rp) && eq_expr(li, ri) && eq_block(lt, rt) && la == ra,
         (Loop(lt, ll, _), Loop(rt, rl, _)) => eq_label(ll, rl) && eq_block(lt, rt),
         (Block(lb, ll), Block(rb, rl)) => eq_label(ll, rl) && eq_block(lb, rb),
         (TryBlock(l), TryBlock(r)) => eq_block(l, r),
diff --git a/src/tools/clippy/clippy_utils/src/sugg.rs b/src/tools/clippy/clippy_utils/src/sugg.rs
@@ -197,7 +197,7 @@ impl<'a> Sugg<'a> {
             | ast::ExprKind::Continue(..)
             | ast::ExprKind::Yield(..)
             | ast::ExprKind::Field(..)
-            | ast::ExprKind::ForLoop(..)
+            | ast::ExprKind::ForLoop { .. }
             | ast::ExprKind::Index(..)
             | ast::ExprKind::InlineAsm(..)
             | ast::ExprKind::OffsetOf(..)
diff --git a/src/tools/rustfmt/src/closures.rs b/src/tools/rustfmt/src/closures.rs
@@ -438,7 +438,7 @@ fn is_block_closure_forced(context: &RewriteContext<'_>, expr: &ast::Expr) -> bo
 
 fn is_block_closure_forced_inner(expr: &ast::Expr, version: Version) -> bool {
     match expr.kind {
-        ast::ExprKind::If(..) | ast::ExprKind::While(..) | ast::ExprKind::ForLoop(..) => true,
+        ast::ExprKind::If(..) | ast::ExprKind::While(..) | ast::ExprKind::ForLoop { .. } => true,
         ast::ExprKind::Loop(..) if version == Version::Two => true,
         ast::ExprKind::AddrOf(_, _, ref expr)
         | ast::ExprKind::Try(ref expr)
@@ -463,7 +463,7 @@ fn expr_requires_semi_to_be_stmt(e: &ast::Expr) -> bool {
         | ast::ExprKind::Block(..)
         | ast::ExprKind::While(..)
         | ast::ExprKind::Loop(..)
-        | ast::ExprKind::ForLoop(..)
+        | ast::ExprKind::ForLoop{ ..}
         | ast::ExprKind::TryBlock(..) => false,
         _ => true,
     }
diff --git a/src/tools/rustfmt/src/expr.rs b/src/tools/rustfmt/src/expr.rs
@@ -134,7 +134,7 @@ pub(crate) fn format_expr(
         }
         ast::ExprKind::Let(ref pat, ref expr, _span, _) => rewrite_let(context, shape, pat, expr),
         ast::ExprKind::If(..)
-        | ast::ExprKind::ForLoop(..)
+        | ast::ExprKind::ForLoop { .. }
         | ast::ExprKind::Loop(..)
         | ast::ExprKind::While(..) => to_control_flow(expr, expr_type)
             .and_then(|control_flow| control_flow.rewrite(context, shape)),
@@ -682,9 +682,15 @@ fn to_control_flow(expr: &ast::Expr, expr_type: ExprType) -> Option<ControlFlow<
                 expr.span,
             ))
         }
-        ast::ExprKind::ForLoop(ref pat, ref cond, ref block, label) => {
-            Some(ControlFlow::new_for(pat, cond, block, label, expr.span))
-        }
+        ast::ExprKind::ForLoop {
+            ref pat,
+            ref iter,
+            ref body,
+            label,
+            is_await,
+        } => Some(ControlFlow::new_for(
+            pat, iter, body, label, expr.span, is_await,
+        )),
         ast::ExprKind::Loop(ref block, label, _) => {
             Some(ControlFlow::new_loop(block, label, expr.span))
         }
@@ -771,14 +777,15 @@ impl<'a> ControlFlow<'a> {
         block: &'a ast::Block,
         label: Option<ast::Label>,
         span: Span,
+        is_await: bool,
     ) -> ControlFlow<'a> {
         ControlFlow {
             cond: Some(cond),
             block,
             else_block: None,
             label,
             pat: Some(pat),
-            keyword: "for",
+            keyword: if is_await { "for await" } else { "for" },
             matcher: "",
             connector: " in",
             allow_single_line: false,
@@ -1364,7 +1371,7 @@ pub(crate) fn can_be_overflowed_expr(
                 || context.config.overflow_delimited_expr()
         }
         ast::ExprKind::If(..)
-        | ast::ExprKind::ForLoop(..)
+        | ast::ExprKind::ForLoop { .. }
         | ast::ExprKind::Loop(..)
         | ast::ExprKind::While(..) => {
             context.config.combine_control_expr() && context.use_block_indent() && args_len == 1
diff --git a/src/tools/rustfmt/src/matches.rs b/src/tools/rustfmt/src/matches.rs
@@ -591,7 +591,7 @@ fn can_flatten_block_around_this(body: &ast::Expr) -> bool {
         ast::ExprKind::If(..) => false,
         // We do not allow collapsing a block around expression with condition
         // to avoid it being cluttered with match arm.
-        ast::ExprKind::ForLoop(..) | ast::ExprKind::While(..) => false,
+        ast::ExprKind::ForLoop { .. } | ast::ExprKind::While(..) => false,
         ast::ExprKind::Loop(..)
         | ast::ExprKind::Match(..)
         | ast::ExprKind::Block(..)
diff --git a/src/tools/rustfmt/src/overflow.rs b/src/tools/rustfmt/src/overflow.rs
diff --git a/src/tools/rustfmt/src/utils.rs b/src/tools/rustfmt/src/utils.rs

Original file line number	Diff line number	Diff line change
`@@ -1388,7 +1388,7 @@ pub fn noop_visit_expr<T: MutVisitor>(`
`1388`	`1388`	`vis.visit_block(body);`
`1389`	`1389`	`visit_opt(label, \|label\| vis.visit_label(label));`
`1390`	`1390`	`}`
`1391`		`- ExprKind::ForLoop(pat, iter, body, label) => {`
	`1391`	`+ ExprKind::ForLoop{pat, iter, body, label, is_await: _} => {`
`1392`	`1392`	`vis.visit_pat(pat);`
`1393`	`1393`	`vis.visit_expr(iter);`
`1394`	`1394`	`vis.visit_block(body);`
Original file line number	Diff line number	Diff line change
`@@ -852,8 +852,8 @@ trait UnusedDelimLint {`
`852`	`852`	`(cond, UnusedDelimsCtx::WhileCond, true, Some(left), Some(right), true)`
`853`	`853`	`}`
`854`	`854`
`855`		`- ForLoop(_, ref cond, ref block, ..) => {`
`856`		`- (cond, UnusedDelimsCtx::ForIterExpr, true, None, Some(block.span.lo()), true)`
	`855`	`+ ForLoop { ref iter, ref body, .. } => {`
	`856`	`+ (iter, UnusedDelimsCtx::ForIterExpr, true, None, Some(body.span.lo()), true)`
`857`	`857`	`}`
`858`	`858`
`859`	`859`	`Match(ref head, _) if Self::LINT_EXPR_IN_PATTERN_MATCHING_CTX => {`
`@@ -1085,7 +1085,7 @@ impl EarlyLintPass for UnusedParens {`
`1085`	`1085`	`}`
`1086`	`1086`
`1087`	`1087`	`match e.kind {`
`1088`		`- ExprKind::Let(ref pat, _, _, _) \| ExprKind::ForLoop(ref pat, ..) => {`
	`1088`	`+ ExprKind::Let(ref pat, _, _, _) \| ExprKind::ForLoop { ref pat, .. } => {`
`1089`	`1089`	`self.check_unused_parens_pat(cx, pat, false, false, (true, true));`
`1090`	`1090`	`}`
`1091`	`1091`	// We ignore parens in cases like `if (((let Some(0) = Some(1))))` because we already
Original file line number	Diff line number	Diff line change
`@@ -4246,11 +4246,11 @@ impl<'a: 'ast, 'b, 'ast, 'tcx> LateResolutionVisitor<'a, 'b, 'ast, 'tcx> {`
`4246`	`4246`	`});`
`4247`	`4247`	`}`
`4248`	`4248`
`4249`		`- ExprKind::ForLoop(ref pat, ref iter_expr, ref block, label) => {`
`4250`		`- self.visit_expr(iter_expr);`
	`4249`	`+ ExprKind::ForLoop { ref pat, ref iter, ref body, label, is_await: _ } => {`
	`4250`	`+ self.visit_expr(iter);`
`4251`	`4251`	`self.with_rib(ValueNS, RibKind::Normal, \|this\| {`
`4252`	`4252`	`this.resolve_pattern_top(pat, PatternSource::For);`
`4253`		`- this.resolve_labeled_block(label, expr.id, block);`
	`4253`	`+ this.resolve_labeled_block(label, expr.id, body);`
`4254`	`4254`	`});`
`4255`	`4255`	`}`
`4256`	`4256`