Merge pull request rust-lang#5 from mojave2/lint_loop_exit

new_lint loop_without_break_or_return

Author: surechen

CHANGELOG.md

@@ -4652,6 +4652,7 @@ Released 2018-09-13
 [`lines_filter_map_ok`]: https://rust-lang.github.io/rust-clippy/master/index.html#lines_filter_map_ok
 [`linkedlist`]: https://rust-lang.github.io/rust-clippy/master/index.html#linkedlist
 [`logic_bug`]: https://rust-lang.github.io/rust-clippy/master/index.html#logic_bug
+[`loop_without_break_or_return`]: https://rust-lang.github.io/rust-clippy/master/index.html#loop_without_break_or_return
 [`lossy_float_literal`]: https://rust-lang.github.io/rust-clippy/master/index.html#lossy_float_literal
 [`macro_use_imports`]: https://rust-lang.github.io/rust-clippy/master/index.html#macro_use_imports
 [`main_recursion`]: https://rust-lang.github.io/rust-clippy/master/index.html#main_recursion

clippy_lints/src/declared_lints.rs

@@ -244,6 +244,7 @@ pub(crate) static LINTS: &[&crate::LintInfo] = &[
     crate::literal_representation::MISTYPED_LITERAL_SUFFIXES_INFO,
     crate::literal_representation::UNREADABLE_LITERAL_INFO,
     crate::literal_representation::UNUSUAL_BYTE_GROUPINGS_INFO,
+    crate::loop_without_break_or_return::LOOP_WITHOUT_BREAK_OR_RETURN_INFO,
     crate::loops::EMPTY_LOOP_INFO,
     crate::loops::EXPLICIT_COUNTER_LOOP_INFO,
     crate::loops::EXPLICIT_INTO_ITER_LOOP_INFO,

clippy_lints/src/lib.rs

@@ -173,6 +173,7 @@ mod let_with_type_underscore;
 mod lifetimes;
 mod lines_filter_map_ok;
 mod literal_representation;
+mod loop_without_break_or_return;
 mod loops;
 mod macro_use;
 mod main_recursion;
@@ -968,6 +969,7 @@ pub fn register_plugins(store: &mut rustc_lint::LintStore, sess: &Session, conf:
     store.register_late_pass(|_| Box::new(unsafe_block_in_proc_macro::UnsafeBlockInProcMacro::new()));
     store.register_early_pass(|| Box::new(implicit_abi::ImplicitAbi));
     store.register_early_pass(|| Box::new(non_reentrant_functions::NonReentrantFunctions));
+    store.register_early_pass(|| Box::new(loop_without_break_or_return::LoopWithoutBreakOrReturn));
     // add lints here, do not remove this comment, it's used in `new_lint`
 }
 

clippy_lints/src/loop_without_break_or_return.rs

@@ -0,0 +1,82 @@
+use clippy_utils::diagnostics::span_lint;
+use rustc_ast::ast::{Block, Expr, ExprKind, Label, StmtKind};
+use rustc_lint::{EarlyContext, EarlyLintPass};
+use rustc_session::{declare_lint_pass, declare_tool_lint};
+
+declare_clippy_lint! {
+    /// ### What it does
+    /// Checks for loop-without-exit-mechanism.
+    ///
+    /// ### Why is this bad?
+    /// This makes code bug-prone.
+    ///
+    /// ### Example
+    /// ```rust
+    /// loop {
+    ///     println!("so something");
+    /// }
+    /// ```
+    /// Use instead:
+    /// ```rust
+    /// loop {
+    ///     println!("do something");
+    ///     if flag {
+    ///         break;
+    ///     }
+    /// }
+    /// ```
+    #[clippy::version = "1.70.0"]
+    pub LOOP_WITHOUT_BREAK_OR_RETURN,
+    nursery,
+    "loop block without `break` or `return` statement"
+}
+declare_lint_pass!(LoopWithoutBreakOrReturn => [LOOP_WITHOUT_BREAK_OR_RETURN]);
+
+impl EarlyLintPass for LoopWithoutBreakOrReturn {
+    fn check_expr(&mut self, cx: &EarlyContext<'_>, expr: &Expr) {
+        if expr.span.from_expansion() {
+            return;
+        }
+
+        let msg: &str = "consider adding `break` or `return` statement in the loop block";
+
+        if let ExprKind::Loop(block, label, _) = &expr.kind {
+            if !check_block(block, label, true) {
+                span_lint(cx, LOOP_WITHOUT_BREAK_OR_RETURN, expr.span, msg);
+            }
+        }
+    }
+}
+
+fn check_block(block: &Block, label: &Option<Label>, outest: bool) -> bool {
+    block.stmts.iter().any(|stmt| match &stmt.kind {
+        StmtKind::Semi(expr) | StmtKind::Expr(expr) => !expr.span.from_expansion() && check_expr(expr, label, outest),
+        _ => false,
+    })
+}
+
+fn check_expr(expr: &Expr, label: &Option<Label>, outest: bool) -> bool {
+    match &expr.kind {
+        ExprKind::Ret(..) => true,
+        ExprKind::Break(lbl, _) => {
+            if outest {
+                true
+            } else {
+                label.is_some() && label == lbl
+            }
+        },
+        ExprKind::If(_, blk, else_expr) => {
+            let mut do_exit = check_block(blk, label, outest);
+            if let Some(expr) = else_expr {
+                do_exit = do_exit || check_expr(expr, label, outest);
+            }
+            do_exit
+        },
+        ExprKind::Loop(blk, ..) | ExprKind::ForLoop(_, _, blk, _) | ExprKind::While(_, blk, _) => {
+            check_block(blk, label, false)
+        },
+        ExprKind::Block(blk, _) | ExprKind::Async(_, blk) => check_block(blk, label, outest),
+        ExprKind::Match(_, arms) => arms.iter().any(|arm| check_expr(&arm.body, label, outest)),
+        _ => false,
+    }
+}

tests/ui/loop_without_break_or_return.rs

@@ -0,0 +1,102 @@
+#![allow(unused, clippy::never_loop)]
+#![warn(clippy::loop_without_break_or_return)]
+
+fn test_01() {
+    loop {
+        println!("Hello, Rust!");
+    }
+
+    loop {
+        break;
+    }
+
+    'outer: loop {
+        break 'outer;
+    }
+
+    'outer: loop {
+        break;
+    }
+}
+
+fn test_02() {
+    loop {
+        if 2 < 3 {
+            break;
+        }
+    }
+}
+
+fn test_03() {
+    'outer1: loop {
+        for x in 0..5 {
+            if x == 3 {
+                break 'outer1;
+            }
+        }
+    }
+
+    'outer2: loop {
+        for x in 0..5 {
+            if x == 3 {
+                break;
+            }
+        }
+    }
+
+    'outer3: loop {
+        for x in 0..5 {
+            if x == 3 {
+                println!("Hello, Rust!");
+            } else {
+                break 'outer3;
+            }
+        }
+    }
+}
+
+fn test_04() {
+    'outer1: loop {
+        loop {
+            println!("Hello, Rust!");
+        }
+        break;
+    }
+
+    'outer2: loop {
+        loop {
+            break;
+        }
+    }
+
+    'outer3: loop {
+        loop {
+            break 'outer3;
+        }
+    }
+
+    'outer4: loop {
+        'inner: loop {
+            loop {
+                break 'inner;
+            }
+        }
+    }
+
+    'outer5: loop {
+        loop {
+            'inner: loop {
+                loop {
+                    loop {
+                        break 'inner;
+                    }
+                    break 'outer5;
+                }
+            }
+        }
+    }
+}
+
+fn main() {
+    // test code goes here
+}

tests/ui/loop_without_break_or_return.stderr

@@ -0,0 +1,66 @@
+error: consider adding `break` or `return` statement in the loop block
+  --> $DIR/loop_without_break_or_return.rs:5:5
+   |
+LL | /     loop {
+LL | |         println!("Hello, Rust!");
+LL | |     }
+   | |_____^
+   |
+   = note: `-D clippy::loop-without-break-or-return` implied by `-D warnings`
+
+error: consider adding `break` or `return` statement in the loop block
+  --> $DIR/loop_without_break_or_return.rs:39:5
+   |
+LL | /     'outer2: loop {
+LL | |         for x in 0..5 {
+LL | |             if x == 3 {
+LL | |                 break;
+LL | |             }
+LL | |         }
+LL | |     }
+   | |_____^
+
+error: consider adding `break` or `return` statement in the loop block
+  --> $DIR/loop_without_break_or_return.rs:60:9
+   |
+LL | /         loop {
+LL | |             println!("Hello, Rust!");
+LL | |         }
+   | |_________^
+
+error: consider adding `break` or `return` statement in the loop block
+  --> $DIR/loop_without_break_or_return.rs:66:5
+   |
+LL | /     'outer2: loop {
+LL | |         loop {
+LL | |             break;
+LL | |         }
+LL | |     }
+   | |_____^
+
+error: consider adding `break` or `return` statement in the loop block
+  --> $DIR/loop_without_break_or_return.rs:78:5
+   |
+LL | /     'outer4: loop {
+LL | |         'inner: loop {
+LL | |             loop {
+LL | |                 break 'inner;
+LL | |             }
+LL | |         }
+LL | |     }
+   | |_____^
+
+error: consider adding `break` or `return` statement in the loop block
+  --> $DIR/loop_without_break_or_return.rs:87:9
+   |
+LL | /         loop {
+LL | |             'inner: loop {
+LL | |                 loop {
+LL | |                     loop {
+...  |
+LL | |             }
+LL | |         }
+   | |_________^
+
+error: aborting due to 6 previous errors
+