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fix never_loop

This commit is contained in:
Cameron Steffen 2017-05-30 20:44:01 -05:00
parent 892cc2833c
commit 20728fb0d0
5 changed files with 133 additions and 72 deletions
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2
README.md
View File

@ -295,7 +295,7 @@ name
[needless_return](https://github.com/Manishearth/rust-clippy/wiki#needless_return) | warn | using a return statement like `return expr;` where an expression would suffice
[needless_update](https://github.com/Manishearth/rust-clippy/wiki#needless_update) | warn | using `Foo { ..base }` when there are no missing fields
[neg_multiply](https://github.com/Manishearth/rust-clippy/wiki#neg_multiply) | warn | multiplying integers with -1
[never_loop](https://github.com/Manishearth/rust-clippy/wiki#never_loop) | allow | any loop with an unconditional `break` or `return` statement
[never_loop](https://github.com/Manishearth/rust-clippy/wiki#never_loop) | warn | any loop that will always `break` or `return`
[new_ret_no_self](https://github.com/Manishearth/rust-clippy/wiki#new_ret_no_self) | warn | not returning `Self` in a `new` method
[new_without_default](https://github.com/Manishearth/rust-clippy/wiki#new_without_default) | warn | `fn new() -> Self` method without `Default` implementation
[new_without_default_derive](https://github.com/Manishearth/rust-clippy/wiki#new_without_default_derive) | warn | `fn new() -> Self` without `#[derive]`able `Default` implementation

2
clippy_lints/src/lib.rs
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@ -324,7 +324,6 @@ pub fn register_plugins(reg: &mut rustc_plugin::Registry) {
enum_variants::STUTTER,
if_not_else::IF_NOT_ELSE,
items_after_statements::ITEMS_AFTER_STATEMENTS,
loops::NEVER_LOOP,
matches::SINGLE_MATCH_ELSE,
mem_forget::MEM_FORGET,
methods::FILTER_MAP,
@ -420,6 +419,7 @@ pub fn register_plugins(reg: &mut rustc_plugin::Registry) {
loops::FOR_LOOP_OVER_RESULT,
loops::ITER_NEXT_LOOP,
loops::NEEDLESS_RANGE_LOOP,
loops::NEVER_LOOP,
loops::REVERSE_RANGE_LOOP,
loops::UNUSED_COLLECT,
loops::WHILE_LET_LOOP,

107
clippy_lints/src/loops.rs
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@ -285,15 +285,13 @@ declare_lint! {
"looping on a map using `iter` when `keys` or `values` would do"
}
/// **What it does:** Checks for loops that contain an unconditional `break`
/// or `return`.
/// **What it does:** Checks for loops that will always `break`, `return` or
/// `continue` an outer loop.
///
/// **Why is this bad?** This loop never loops, all it does is obfuscating the
/// code.
///
/// **Known problems:** Ignores `continue` statements in the loop that create
/// nontrivial control flow. Therefore set to `Allow` by default.
/// See https://github.com/Manishearth/rust-clippy/issues/1586
/// **Known problems:** None
///
/// **Example:**
/// ```rust
@ -301,8 +299,8 @@ declare_lint! {
/// ```
declare_lint! {
pub NEVER_LOOP,
Allow,
"any loop with an unconditional `break` or `return` statement"
Warn,
"any loop that will always `break` or `return`"
}
#[derive(Copy, Clone)]
@ -344,7 +342,7 @@ impl<'a, 'tcx> LateLintPass<'a, 'tcx> for Pass {
"empty `loop {}` detected. You may want to either use `panic!()` or add \
`std::thread::sleep(..);` to the loop body.");
}
if never_loop_block(block) {
if never_loop(block, &expr.id) {
span_lint(cx, NEVER_LOOP, expr.span, "this loop never actually loops");
}
@ -424,47 +422,100 @@ impl<'a, 'tcx> LateLintPass<'a, 'tcx> for Pass {
}
}
fn never_loop_block(block: &Block) -> bool {
block.stmts.iter().any(never_loop_stmt) || block.expr.as_ref().map_or(false, |e| never_loop_expr(e))
fn never_loop(block: &Block, id: &NodeId) -> bool {
!contains_continue_block(block, id) && loop_exit_block(block)
}
fn never_loop_stmt(stmt: &Stmt) -> bool {
fn contains_continue_block(block: &Block, dest: &NodeId) -> bool {
block.stmts.iter().any(|e| contains_continue_stmt(e, dest))
|| block.expr.as_ref().map_or(false, |e| contains_continue_expr(e, dest))
}
fn contains_continue_stmt(stmt: &Stmt, dest: &NodeId) -> bool {
match stmt.node {
StmtSemi(ref e, _) |
StmtExpr(ref e, _) => never_loop_expr(e),
StmtDecl(ref d, _) => never_loop_decl(d),
StmtExpr(ref e, _) => contains_continue_expr(e, dest),
StmtDecl(ref d, _) => contains_continue_decl(d, dest),
}
}
fn never_loop_decl(decl: &Decl) -> bool {
if let DeclLocal(ref local) = decl.node {
local.init.as_ref().map_or(false, |e| never_loop_expr(e))
} else {
false
fn contains_continue_decl(decl: &Decl, dest: &NodeId) -> bool {
match decl.node {
DeclLocal(ref local) => local.init.as_ref().map_or(false, |e| contains_continue_expr(e, dest)),
_ => false
}
}
fn never_loop_expr(expr: &Expr) -> bool {
fn contains_continue_expr(expr: &Expr, dest: &NodeId) -> bool {
match expr.node {
ExprBreak(..) | ExprRet(..) => true,
ExprBox(ref e) |
ExprUnary(_, ref e) |
ExprBinary(_, ref e, _) | // because short-circuiting
ExprCast(ref e, _) |
ExprType(ref e, _) |
ExprField(ref e, _) |
ExprTupField(ref e, _) |
ExprRepeat(ref e, _) |
ExprAddrOf(_, ref e) => never_loop_expr(e),
ExprAddrOf(_, ref e) |
ExprRepeat(ref e, _) => contains_continue_expr(e, dest),
ExprBinary(_, ref e1, ref e2) |
ExprAssign(ref e1, ref e2) |
ExprAssignOp(_, ref e1, ref e2) |
ExprIndex(ref e1, ref e2) => never_loop_expr(e1) || never_loop_expr(e2),
ExprIndex(ref e1, ref e2) => [e1, e2].iter().any(|e| contains_continue_expr(e, dest)),
ExprArray(ref es) |
ExprTup(ref es) |
ExprMethodCall(_, _, ref es) => es.iter().any(|e| never_loop_expr(e)),
ExprCall(ref e, ref es) => never_loop_expr(e) || es.iter().any(|e| never_loop_expr(e)),
ExprBlock(ref block) => never_loop_block(block),
ExprStruct(_, _, ref base) => base.as_ref().map_or(false, |e| never_loop_expr(e)),
ExprMethodCall(_, _, ref es) => es.iter().any(|e| contains_continue_expr(e, dest)),
ExprCall(ref e, ref es) => contains_continue_expr(e, dest) || es.iter().any(|e| contains_continue_expr(e, dest)),
ExprBlock(ref block) => contains_continue_block(block, dest),
ExprStruct(_, _, ref base) => base.as_ref().map_or(false, |e| contains_continue_expr(e, dest)),
ExprAgain(d) => d.target_id.opt_id().map_or(false, |id| id == *dest),
_ => false,
}
}
fn loop_exit_block(block: &Block) -> bool {
block.stmts.iter().any(|e| loop_exit_stmt(e))
|| block.expr.as_ref().map_or(false, |e| loop_exit_expr(e))
}
fn loop_exit_stmt(stmt: &Stmt) -> bool {
match stmt.node {
StmtSemi(ref e, _) |
StmtExpr(ref e, _) => loop_exit_expr(e),
StmtDecl(ref d, _) => loop_exit_decl(d),
}
}
fn loop_exit_decl(decl: &Decl) -> bool {
match decl.node {
DeclLocal(ref local) => local.init.as_ref().map_or(false, |e| loop_exit_expr(e)),
_ => false
}
}
fn loop_exit_expr(expr: &Expr) -> bool {
match expr.node {
ExprBox(ref e) |
ExprUnary(_, ref e) |
ExprCast(ref e, _) |
ExprType(ref e, _) |
ExprField(ref e, _) |
ExprTupField(ref e, _) |
ExprAddrOf(_, ref e) |
ExprRepeat(ref e, _) => loop_exit_expr(e),
ExprMethodCall(_, _, ref es) => es.iter().any(|e| loop_exit_expr(e)),
ExprArray(ref es) |
ExprTup(ref es) => es.iter().any(|e| loop_exit_expr(e)),
ExprCall(ref e, ref es) => loop_exit_expr(e) || es.iter().any(|e| loop_exit_expr(e)),
ExprBinary(_, ref e1, ref e2) |
ExprAssign(ref e1, ref e2) |
ExprAssignOp(_, ref e1, ref e2) |
ExprIndex(ref e1, ref e2) => [e1, e2].iter().any(|e| loop_exit_expr(e)),
ExprIf(ref e, ref e2, ref e3) => loop_exit_expr(e) || e3.as_ref().map_or(false, |e| loop_exit_expr(e)) && loop_exit_expr(e2),
ExprWhile(ref e, ref b, _) => loop_exit_expr(e) || loop_exit_block(b),
ExprMatch(ref e, ref arms, _) => loop_exit_expr(e) || arms.iter().all(|a| loop_exit_expr(&a.body)),
ExprBlock(ref b) => loop_exit_block(b),
ExprBreak(_, _) |
ExprAgain(_) |
ExprRet(_) => true,
_ => false,
}
}

63
clippy_tests/examples/never_loop.rs
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@ -2,33 +2,56 @@
#![plugin(clippy)]
#![warn(never_loop)]
#![allow(dead_code, unused)]
#![allow(single_match, while_true)]
fn main() {
fn break_stmt() {
loop {
println!("This is only ever printed once");
break;
}
}
let x = 1;
fn conditional_break() {
let mut x = 5;
loop {
println!("This, too"); // but that's OK
x -= 1;
if x == 1 {
break;
}
}
loop {
loop {
// another one
break;
}
break;
}
loop {
loop {
if x == 1 { return; }
break
}
}
}
fn nested_loop() {
loop {
while true {
break
}
break
}
}
fn if_false() {
let x = 1;
loop {
if x == 1 {
return
}
}
}
fn match_false() {
let x = 1;
loop {
match x {
1 => return,
_ => (),
}
}
}
fn main() {
break_stmt();
conditional_break();
nested_loop();
if_false();
match_false();
}

31
clippy_tests/examples/never_loop.stderr
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@ -2,38 +2,25 @@ error: this loop never actually loops
--> never_loop.rs:8:5
|
8 | / loop {
9 | | println!("This is only ever printed once");
10 | | break;
11 | | }
9 | | break;
10 | | }
| |_____^
|
= note: `-D never-loop` implied by `-D warnings`
error: this loop never actually loops
--> never_loop.rs:21:5
--> never_loop.rs:24:5
|
21 | / loop {
22 | | loop {
23 | | // another one
24 | | break;
25 | | }
26 | | break;
27 | | }
24 | / loop {
25 | | while true {
26 | | break
27 | | }
28 | | break
29 | | }
| |_____^
|
= note: `-D never-loop` implied by `-D warnings`
error: this loop never actually loops
--> never_loop.rs:22:9
|
22 | / loop {
23 | | // another one
24 | | break;
25 | | }
| |_________^
|
= note: `-D never-loop` implied by `-D warnings`
error: aborting due to previous error(s)
error: Could not compile `clippy_tests`.