Rollup merge of rust-lang#50793 - jrlusby:master, r=petrochenkov

tidy: Add a check for empty UI test files

Check for empty `.stderr` and `.stdout` files in UI test directories.
Empty files could  still pass testing for `compile-pass` tests with no output
so they can get into the repo accidentally, but they are not necessary and can
be removed.

This is very much an in progress pull request. I'm having an issue with rustfmt. It wanted to reformat the entire file for almost every file by default. And when I run tidy it just errors out because it catches the empty files that are already in the repo.

My next step is goin got be to remove those empty file and see if running tidy again will actually reformat things outside of the context of `cargo fmt`

Fixes rust-lang#50785

Author: kennytm

src/librustc/cfg/construct.rs

@@ -179,7 +179,7 @@ impl<'a, 'tcx> CFGBuilder<'a, 'tcx> {
 
     fn expr(&mut self, expr: &hir::Expr, pred: CFGIndex) -> CFGIndex {
         match expr.node {
-            hir::ExprBlock(ref blk) => {
+            hir::ExprBlock(ref blk, _) => {
                 let blk_exit = self.block(&blk, pred);
                 self.add_ast_node(expr.hir_id.local_id, &[blk_exit])
             }

src/librustc/hir/intravisit.rs

@@ -1015,7 +1015,10 @@ pub fn walk_expr<'v, V: Visitor<'v>>(visitor: &mut V, expression: &'v Expr) {
                              expression.span,
                              expression.id)
         }
-        ExprBlock(ref block) => visitor.visit_block(block),
+        ExprBlock(ref block, ref opt_label) => {
+            walk_list!(visitor, visit_label, opt_label);
+            visitor.visit_block(block);
+        }
         ExprAssign(ref left_hand_expression, ref right_hand_expression) => {
             visitor.visit_expr(right_hand_expression);
             visitor.visit_expr(left_hand_expression)

src/librustc/hir/lowering.rs

@@ -3048,7 +3048,7 @@ impl<'a> LoweringContext<'a> {
                     );
                     block.expr = Some(this.wrap_in_try_constructor(
                         "from_ok", tail, unstable_span));
-                    hir::ExprBlock(P(block))
+                    hir::ExprBlock(P(block), None)
                 })
             }
             ExprKind::Match(ref expr, ref arms) => hir::ExprMatch(
@@ -3100,7 +3100,11 @@ impl<'a> LoweringContext<'a> {
                     })
                 })
             }
-            ExprKind::Block(ref blk) => hir::ExprBlock(self.lower_block(blk, false)),
+            ExprKind::Block(ref blk, opt_label) => {
+                hir::ExprBlock(self.lower_block(blk,
+                                                opt_label.is_some()),
+                                                self.lower_label(opt_label))
+            }
             ExprKind::Assign(ref el, ref er) => {
                 hir::ExprAssign(P(self.lower_expr(el)), P(self.lower_expr(er)))
             }
@@ -3843,7 +3847,7 @@ impl<'a> LoweringContext<'a> {
     }
 
     fn expr_block(&mut self, b: P<hir::Block>, attrs: ThinVec<Attribute>) -> hir::Expr {
-        self.expr(b.span, hir::ExprBlock(b), attrs)
+        self.expr(b.span, hir::ExprBlock(b, None), attrs)
     }
 
     fn expr_tuple(&mut self, sp: Span, exprs: hir::HirVec<hir::Expr>) -> P<hir::Expr> {

src/librustc/hir/mod.rs

@@ -778,9 +778,8 @@ pub struct Block {
     pub rules: BlockCheckMode,
     pub span: Span,
     /// If true, then there may exist `break 'a` values that aim to
-    /// break out of this block early. As of this writing, this is not
-    /// currently permitted in Rust itself, but it is generated as
-    /// part of `catch` statements.
+    /// break out of this block early.
+    /// Used by `'label: {}` blocks and by `catch` statements.
     pub targeted_by_break: bool,
     /// If true, don't emit return value type errors as the parser had
     /// to recover from a parse error so this block will not have an
@@ -1381,8 +1380,8 @@ pub enum Expr_ {
     /// This may also be a generator literal, indicated by the final boolean,
     /// in that case there is an GeneratorClause.
     ExprClosure(CaptureClause, P<FnDecl>, BodyId, Span, Option<GeneratorMovability>),
-    /// A block (`{ ... }`)
-    ExprBlock(P<Block>),
+    /// A block (`'label: { ... }`)
+    ExprBlock(P<Block>, Option<Label>),
 
     /// An assignment (`a = foo()`)
     ExprAssign(P<Expr>, P<Expr>),

src/librustc/hir/print.rs

@@ -1047,7 +1047,7 @@ impl<'a> State<'a> {
                         self.print_else(e.as_ref().map(|e| &**e))
                     }
                     // "final else"
-                    hir::ExprBlock(ref b) => {
+                    hir::ExprBlock(ref b, _) => {
                         self.cbox(indent_unit - 1)?;
                         self.ibox(0)?;
                         self.s.word(" else ")?;
@@ -1377,7 +1377,11 @@ impl<'a> State<'a> {
                 // empty box to satisfy the close.
                 self.ibox(0)?;
             }
-            hir::ExprBlock(ref blk) => {
+            hir::ExprBlock(ref blk, opt_label) => {
+                if let Some(label) = opt_label {
+                    self.print_name(label.name)?;
+                    self.word_space(":")?;
+                }
                 // containing cbox, will be closed by print-block at }
                 self.cbox(indent_unit)?;
                 // head-box, will be closed by print-block after {
@@ -1893,7 +1897,11 @@ impl<'a> State<'a> {
         self.word_space("=>")?;
 
         match arm.body.node {
-            hir::ExprBlock(ref blk) => {
+            hir::ExprBlock(ref blk, opt_label) => {
+                if let Some(label) = opt_label {
+                    self.print_name(label.name)?;
+                    self.word_space(":")?;
+                }
                 // the block will close the pattern's ibox
                 self.print_block_unclosed_indent(&blk, indent_unit)?;
 
@@ -2299,7 +2307,7 @@ fn expr_requires_semi_to_be_stmt(e: &hir::Expr) -> bool {
     match e.node {
         hir::ExprIf(..) |
         hir::ExprMatch(..) |
-        hir::ExprBlock(_) |
+        hir::ExprBlock(..) |
         hir::ExprWhile(..) |
         hir::ExprLoop(..) => false,
         _ => true,

src/librustc/ich/impls_hir.rs

@@ -589,7 +589,7 @@ impl_stable_hash_for!(enum hir::Expr_ {
     ExprLoop(body, label, loop_src),
     ExprMatch(matchee, arms, match_src),
     ExprClosure(capture_clause, decl, body_id, span, gen),
-    ExprBlock(blk),
+    ExprBlock(blk, label),
     ExprAssign(lhs, rhs),
     ExprAssignOp(op, lhs, rhs),
     ExprField(owner, field_name),

src/librustc/middle/expr_use_visitor.rs

@@ -499,7 +499,7 @@ impl<'a, 'gcx, 'tcx> ExprUseVisitor<'a, 'gcx, 'tcx> {
                 self.consume_expr(&rhs);
             }
 
-            hir::ExprBlock(ref blk) => {
+            hir::ExprBlock(ref blk, _) => {
                 self.walk_block(&blk);
             }
 

src/librustc/middle/liveness.rs

@@ -1187,7 +1187,9 @@ impl<'a, 'tcx> Liveness<'a, 'tcx> {
             succ
           }
 
-          hir::ExprBlock(ref blk) => {
+          // Note that labels have been resolved, so we don't need to look
+          // at the label ident
+          hir::ExprBlock(ref blk, _) => {
             self.propagate_through_block(&blk, succ)
           }
         }

src/librustc/middle/region.rs

@@ -1247,7 +1247,7 @@ fn resolve_local<'a, 'tcx>(visitor: &mut RegionResolutionVisitor<'a, 'tcx>,
             hir::ExprCast(ref subexpr, _) => {
                 record_rvalue_scope_if_borrow_expr(visitor, &subexpr, blk_id)
             }
-            hir::ExprBlock(ref block) => {
+            hir::ExprBlock(ref block, _) => {
                 if let Some(ref subexpr) = block.expr {
                     record_rvalue_scope_if_borrow_expr(
                         visitor, &subexpr, blk_id);

src/librustc_lint/builtin.rs

@@ -228,7 +228,7 @@ impl UnsafeCode {
 
 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for UnsafeCode {
     fn check_expr(&mut self, cx: &LateContext, e: &hir::Expr) {
-        if let hir::ExprBlock(ref blk) = e.node {
+        if let hir::ExprBlock(ref blk, _) = e.node {
             // Don't warn about generated blocks, that'll just pollute the output.
             if blk.rules == hir::UnsafeBlock(hir::UserProvided) {
                 self.report_unsafe(cx, blk.span, "usage of an `unsafe` block");

src/librustc_mir/build/block.rs

@@ -36,7 +36,7 @@ impl<'a, 'gcx, 'tcx> Builder<'a, 'gcx, 'tcx> {
         self.in_opt_scope(opt_destruction_scope.map(|de|(de, source_info)), block, move |this| {
             this.in_scope((region_scope, source_info), LintLevel::Inherited, block, move |this| {
                 if targeted_by_break {
-                    // This is a `break`-able block (currently only `catch { ... }`)
+                    // This is a `break`-able block
                     let exit_block = this.cfg.start_new_block();
                     let block_exit = this.in_breakable_scope(
                         None, exit_block, destination.clone(), |this| {

src/librustc_mir/hair/cx/expr.rs

@@ -292,7 +292,7 @@ fn make_mirror_unadjusted<'a, 'gcx, 'tcx>(cx: &mut Cx<'a, 'gcx, 'tcx>,
             }
         }
 
-        hir::ExprBlock(ref blk) => ExprKind::Block { body: &blk },
+        hir::ExprBlock(ref blk, _) => ExprKind::Block { body: &blk },
 
         hir::ExprAssign(ref lhs, ref rhs) => {
             ExprKind::Assign {

src/librustc_mir/transform/add_validation.rs

@@ -141,7 +141,7 @@ fn fn_contains_unsafe<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>, src: MirSource) ->
             }
             // Check if this is an unsafe block, or an item
             match node {
-                Node::NodeExpr(&hir::Expr { node: hir::ExprBlock(ref block), ..}) => {
+                Node::NodeExpr(&hir::Expr { node: hir::ExprBlock(ref block, _), ..}) => {
                     if block_is_unsafe(&*block) {
                         // Found an unsafe block, we can bail out here.
                         return true;

src/librustc_passes/diagnostics.rs

@@ -259,6 +259,44 @@ let result = loop { // ok!
     i += 1;
 };
 ```
+"##,
+
+E0695: r##"
+A `break` statement without a label appeared inside a labeled block.
+
+Example of erroneous code:
+
+```compile_fail,E0695
+# #![feature(label_break_value)]
+loop {
+    'a: {
+        break;
+    }
+}
+```
+
+Make sure to always label the `break`:
+
+```
+# #![feature(label_break_value)]
+'l: loop {
+    'a: {
+        break 'l;
+    }
+}
+```
+
+Or if you want to `break` the labeled block:
+
+```
+# #![feature(label_break_value)]
+loop {
+    'a: {
+        break 'a;
+    }
+    break;
+}
+```
 "##
 }
 
@@ -271,4 +309,5 @@ register_diagnostics! {
     E0642, // patterns aren't allowed in methods without bodies
     E0666, // nested `impl Trait` is illegal
     E0667, // `impl Trait` in projections
+    E0696, // `continue` pointing to a labeled block
 }

src/librustc_passes/loops.rs

@@ -13,7 +13,7 @@ use rustc::session::Session;
 
 use rustc::hir::map::Map;
 use rustc::hir::intravisit::{self, Visitor, NestedVisitorMap};
-use rustc::hir;
+use rustc::hir::{self, Destination};
 use syntax::ast;
 use syntax_pos::Span;
 
@@ -39,6 +39,7 @@ enum Context {
     Normal,
     Loop(LoopKind),
     Closure,
+    LabeledBlock,
 }
 
 #[derive(Copy, Clone)]
@@ -84,7 +85,16 @@ impl<'a, 'hir> Visitor<'hir> for CheckLoopVisitor<'a, 'hir> {
             hir::ExprClosure(.., b, _, _) => {
                 self.with_context(Closure, |v| v.visit_nested_body(b));
             }
+            hir::ExprBlock(ref b, Some(_label)) => {
+                self.with_context(LabeledBlock, |v| v.visit_block(&b));
+            }
             hir::ExprBreak(label, ref opt_expr) => {
+                if self.require_label_in_labeled_block(e.span, &label, "break") {
+                    // If we emitted an error about an unlabeled break in a labeled
+                    // block, we don't need any further checking for this break any more
+                    return;
+                }
+
                 let loop_id = match label.target_id.into() {
                     Ok(loop_id) => loop_id,
                     Err(hir::LoopIdError::OutsideLoopScope) => ast::DUMMY_NODE_ID,
@@ -94,6 +104,7 @@ impl<'a, 'hir> Visitor<'hir> for CheckLoopVisitor<'a, 'hir> {
                     },
                     Err(hir::LoopIdError::UnresolvedLabel) => ast::DUMMY_NODE_ID,
                 };
+
                 if loop_id != ast::DUMMY_NODE_ID {
                     match self.hir_map.find(loop_id).unwrap() {
                         hir::map::NodeBlock(_) => return,
@@ -113,13 +124,15 @@ impl<'a, 'hir> Visitor<'hir> for CheckLoopVisitor<'a, 'hir> {
                         })
                     };
                     match loop_kind {
-                        None | Some(LoopKind::Loop(hir::LoopSource::Loop)) => (),
+                        None |
+                        Some(LoopKind::Loop(hir::LoopSource::Loop)) => (),
                         Some(kind) => {
                             struct_span_err!(self.sess, e.span, E0571,
                                              "`break` with value from a `{}` loop",
                                              kind.name())
                                 .span_label(e.span,
-                                            "can only break with a value inside `loop`")
+                                            "can only break with a value inside \
+                                            `loop` or breakable block")
                                 .span_suggestion(e.span,
                                                  &format!("instead, use `break` on its own \
                                                            without a value inside this `{}` loop",
@@ -130,13 +143,29 @@ impl<'a, 'hir> Visitor<'hir> for CheckLoopVisitor<'a, 'hir> {
                     }
                 }
 
-                self.require_loop("break", e.span);
+                self.require_break_cx("break", e.span);
             }
             hir::ExprAgain(label) => {
-                if let Err(hir::LoopIdError::UnlabeledCfInWhileCondition) = label.target_id {
-                    self.emit_unlabled_cf_in_while_condition(e.span, "continue");
+                self.require_label_in_labeled_block(e.span, &label, "continue");
+
+                match label.target_id {
+                    Ok(loop_id) => {
+                        if let hir::map::NodeBlock(block) = self.hir_map.find(loop_id).unwrap() {
+                            struct_span_err!(self.sess, e.span, E0696,
+                                            "`continue` pointing to a labeled block")
+                                .span_label(e.span,
+                                            "labeled blocks cannot be `continue`'d")
+                                .span_note(block.span,
+                                            "labeled block the continue points to")
+                                .emit();
+                        }
+                    }
+                    Err(hir::LoopIdError::UnlabeledCfInWhileCondition) => {
+                        self.emit_unlabled_cf_in_while_condition(e.span, "continue");
+                    }
+                    _ => {}
                 }
-                self.require_loop("continue", e.span)
+                self.require_break_cx("continue", e.span)
             },
             _ => intravisit::walk_expr(self, e),
         }
@@ -153,8 +182,9 @@ impl<'a, 'hir> CheckLoopVisitor<'a, 'hir> {
         self.cx = old_cx;
     }
 
-    fn require_loop(&self, name: &str, span: Span) {
+    fn require_break_cx(&self, name: &str, span: Span) {
         match self.cx {
+            LabeledBlock |
             Loop(_) => {}
             Closure => {
                 struct_span_err!(self.sess, span, E0267, "`{}` inside of a closure", name)
@@ -169,6 +199,22 @@ impl<'a, 'hir> CheckLoopVisitor<'a, 'hir> {
         }
     }
 
+    fn require_label_in_labeled_block(&mut self, span: Span, label: &Destination, cf_type: &str)
+        -> bool
+    {
+        if self.cx == LabeledBlock {
+            if label.label.is_none() {
+                struct_span_err!(self.sess, span, E0695,
+                                "unlabeled `{}` inside of a labeled block", cf_type)
+                    .span_label(span,
+                                format!("`{}` statements that would diverge to or through \
+                                a labeled block need to bear a label", cf_type))
+                    .emit();
+                return true;
+            }
+        }
+        return false;
+    }
     fn emit_unlabled_cf_in_while_condition(&mut self, span: Span, cf_type: &str) {
         struct_span_err!(self.sess, span, E0590,
                          "`break` or `continue` with no label in the condition of a `while` loop")

src/librustc_passes/rvalue_promotion.rs

@@ -342,7 +342,7 @@ fn check_expr<'a, 'tcx>(v: &mut CheckCrateVisitor<'a, 'tcx>, e: &hir::Expr, node
             let mut callee = &**callee;
             loop {
                 callee = match callee.node {
-                    hir::ExprBlock(ref block) => match block.expr {
+                    hir::ExprBlock(ref block, _) => match block.expr {
                         Some(ref tail) => &tail,
                         None => break
                     },
@@ -404,7 +404,7 @@ fn check_expr<'a, 'tcx>(v: &mut CheckCrateVisitor<'a, 'tcx>, e: &hir::Expr, node
             }
         }
 
-        hir::ExprBlock(_) |
+        hir::ExprBlock(..) |
         hir::ExprIndex(..) |
         hir::ExprField(..) |
         hir::ExprArray(_) |

src/librustc_resolve/lib.rs

@@ -3753,6 +3753,8 @@ impl<'a> Resolver<'a> {
                 self.ribs[ValueNS].pop();
             }
 
+            ExprKind::Block(ref block, label) => self.resolve_labeled_block(label, block.id, block),
+
             // Equivalent to `visit::walk_expr` + passing some context to children.
             ExprKind::Field(ref subexpression, _) => {
                 self.resolve_expr(subexpression, Some(expr));