use rustc::lint::*;
use rustc_front::hir::*;
use reexport::*;
use rustc_front::intravisit::{Visitor, walk_expr, walk_block, walk_decl};
use rustc::middle::ty;
use rustc::middle::def::DefLocal;
use consts::{constant_simple, Constant};
use rustc::front::map::Node::{NodeBlock};
use std::borrow::Cow;
use std::collections::{HashSet,HashMap};
use syntax::ast::Lit_::*;
use utils::{snippet, span_lint, get_parent_expr, match_trait_method, match_type,
in_external_macro, expr_block, span_help_and_lint, is_integer_literal,
get_enclosing_block};
use utils::{VEC_PATH, LL_PATH};
/// **What it does:** This lint checks for looping over the range of `0..len` of some collection just to get the values by index. It is `Warn` by default.
///
/// **Why is this bad?** Just iterating the collection itself makes the intent more clear and is probably faster.
///
/// **Known problems:** None
///
/// **Example:**
/// ```
/// for i in 0..vec.len() {
/// println!("{}", vec[i]);
/// }
/// ```
declare_lint!{ pub NEEDLESS_RANGE_LOOP, Warn,
"for-looping over a range of indices where an iterator over items would do" }
/// **What it does:** This lint checks for loops on `x.iter()` where `&x` will do, and suggest the latter. It is `Warn` by default.
///
/// **Why is this bad?** Readability.
///
/// **Known problems:** False negatives. We currently only warn on some known types.
///
/// **Example:** `for x in y.iter() { .. }` (where y is a `Vec` or slice)
declare_lint!{ pub EXPLICIT_ITER_LOOP, Warn,
"for-looping over `_.iter()` or `_.iter_mut()` when `&_` or `&mut _` would do" }
/// **What it does:** This lint checks for loops on `x.next()`. It is `Warn` by default.
///
/// **Why is this bad?** `next()` returns either `Some(value)` if there was a value, or `None` otherwise. The insidious thing is that `Option<_>` implements `IntoIterator`, so that possibly one value will be iterated, leading to some hard to find bugs. No one will want to write such code [except to win an Underhanded Rust Contest](https://www.reddit.com/r/rust/comments/3hb0wm/underhanded_rust_contest/cu5yuhr).
///
/// **Known problems:** None
///
/// **Example:** `for x in y.next() { .. }`
declare_lint!{ pub ITER_NEXT_LOOP, Warn,
"for-looping over `_.next()` which is probably not intended" }
/// **What it does:** This lint detects `loop + match` combinations that are easier written as a `while let` loop.
///
/// **Why is this bad?** The `while let` loop is usually shorter and more readable
///
/// **Known problems:** Sometimes the wrong binding is displayed (#383)
///
/// **Example:**
///
/// ```
/// loop {
/// let x = match y {
/// Some(x) => x,
/// None => break,
/// }
/// // .. do something with x
/// }
/// // is easier written as
/// while let Some(x) = y {
/// // .. do something with x
/// }
/// ```
declare_lint!{ pub WHILE_LET_LOOP, Warn,
"`loop { if let { ... } else break }` can be written as a `while let` loop" }
/// **What it does:** This lint checks for using `collect()` on an iterator without using the result. It is `Warn` by default.
///
/// **Why is this bad?** It is more idiomatic to use a `for` loop over the iterator instead.
///
/// **Known problems:** None
///
/// **Example:** `vec.iter().map(|x| /* some operation returning () */).collect::<Vec<_>>();`
declare_lint!{ pub UNUSED_COLLECT, Warn,
"`collect()`ing an iterator without using the result; this is usually better \
written as a for loop" }
/// **What it does:** This lint checks for loops over ranges `x..y` where both `x` and `y` are constant and `x` is greater or equal to `y`, unless the range is reversed or has a negative `.step_by(_)`.
///
/// **Why is it bad?** Such loops will either be skipped or loop until wrap-around (in debug code, this may `panic!()`). Both options are probably not intended.
///
/// **Known problems:** The lint cannot catch loops over dynamically defined ranges. Doing this would require simulating all possible inputs and code paths through the program, which would be complex and error-prone.
///
/// **Examples**: `for x in 5..10-5 { .. }` (oops, stray `-`)
declare_lint!{ pub REVERSE_RANGE_LOOP, Warn,
"Iterating over an empty range, such as `10..0` or `5..5`" }
/// **What it does:** This lint checks `for` loops over slices with an explicit counter and suggests the use of `.enumerate()`. It is `Warn` by default.
///
/// **Why is it bad?** Not only is the version using `.enumerate()` more readable, the compiler is able to remove bounds checks which can lead to faster code in some instances.
///
/// **Known problems:** None.
///
/// **Example:** `for i in 0..v.len() { foo(v[i]); }` or `for i in 0..v.len() { bar(i, v[i]); }`
declare_lint!{ pub EXPLICIT_COUNTER_LOOP, Warn,
"for-looping with an explicit counter when `_.enumerate()` would do" }
/// **What it does:** This lint checks for empty `loop` expressions. It is `Warn` by default.
///
/// **Why is this bad?** Those busy loops burn CPU cycles without doing anything. Think of the environment and either block on something or at least make the thread sleep for some microseconds.
///
/// **Known problems:** None
///
/// **Example:** `loop {}`
declare_lint!{ pub EMPTY_LOOP, Warn, "empty `loop {}` detected" }
/// **What it does:** This lint checks for `while let` expressions on iterators. It is `Warn` by default.
///
/// **Why is this bad?** Readability. A simple `for` loop is shorter and conveys the intent better.
///
/// **Known problems:** None
///
/// **Example:** `while let Some(val) = iter() { .. }`
declare_lint!{ pub WHILE_LET_ON_ITERATOR, Warn, "using a while-let loop instead of a for loop on an iterator" }
#[derive(Copy, Clone)]
pub struct LoopsPass;
impl LintPass for LoopsPass {
fn get_lints(&self) -> LintArray {
lint_array!(NEEDLESS_RANGE_LOOP, EXPLICIT_ITER_LOOP, ITER_NEXT_LOOP,
WHILE_LET_LOOP, UNUSED_COLLECT, REVERSE_RANGE_LOOP,
EXPLICIT_COUNTER_LOOP, EMPTY_LOOP,
WHILE_LET_ON_ITERATOR)
}
}
impl LateLintPass for LoopsPass {
fn check_expr(&mut self, cx: &LateContext, expr: &Expr) {
if let Some((pat, arg, body)) = recover_for_loop(expr) {
check_for_loop(cx, pat, arg, body, expr);
}
// check for `loop { if let {} else break }` that could be `while let`
// (also matches an explicit "match" instead of "if let")
// (even if the "match" or "if let" is used for declaration)
if let ExprLoop(ref block, _) = expr.node {
// also check for empty `loop {}` statements
if block.stmts.is_empty() && block.expr.is_none() {
span_lint(cx, EMPTY_LOOP, expr.span,
"empty `loop {}` detected. You may want to either \
use `panic!()` or add `std::thread::sleep(..);` to \
the loop body.");
}
// extract the expression from the first statement (if any) in a block
let inner_stmt_expr = extract_expr_from_first_stmt(block);
// or extract the first expression (if any) from the block
if let Some(inner) = inner_stmt_expr.or_else(|| extract_first_expr(block)) {
if let ExprMatch(ref matchexpr, ref arms, ref source) = inner.node {
// collect the remaining statements below the match
let mut other_stuff = block.stmts
.iter()
.skip(1)
.map(|stmt| {
format!("{}", snippet(cx, stmt.span, ".."))
}).collect::<Vec<String>>();
if inner_stmt_expr.is_some() {
// if we have a statement which has a match,
if let Some(ref expr) = block.expr {
// then collect the expression (without semicolon) below it
other_stuff.push(format!("{}", snippet(cx, expr.span, "..")));
}
}
// ensure "if let" compatible match structure
match *source {
MatchSource::Normal | MatchSource::IfLetDesugar{..} => if
arms.len() == 2 &&
arms[0].pats.len() == 1 && arms[0].guard.is_none() &&
arms[1].pats.len() == 1 && arms[1].guard.is_none() &&
// finally, check for "break" in the second clause
is_break_expr(&arms[1].body)
{
if in_external_macro(cx, expr.span) { return; }
let loop_body = if inner_stmt_expr.is_some() {
// FIXME: should probably be an ellipsis
// tabbing and newline is probably a bad idea, especially for large blocks
Cow::Owned(format!("{{\n {}\n}}", other_stuff.join("\n ")))
} else {
expr_block(cx, &arms[0].body, Some(other_stuff.join("\n ")), "..")
};
span_help_and_lint(cx, WHILE_LET_LOOP, expr.span,
"this loop could be written as a `while let` loop",
&format!("try\nwhile let {} = {} {}",
snippet(cx, arms[0].pats[0].span, ".."),
snippet(cx, matchexpr.span, ".."),
loop_body));
},
_ => ()
}
}
}
}
if let ExprMatch(ref match_expr, ref arms, MatchSource::WhileLetDesugar) = expr.node {
let pat = &arms[0].pats[0].node;
if let (&PatEnum(ref path, Some(ref pat_args)),
&ExprMethodCall(method_name, _, ref method_args)) =
(pat, &match_expr.node) {
let iter_expr = &method_args[0];
if let Some(lhs_constructor) = path.segments.last() {
if method_name.node.as_str() == "next" &&
match_trait_method(cx, match_expr, &["core", "iter", "Iterator"]) &&
lhs_constructor.identifier.name.as_str() == "Some" &&
!is_iterator_used_after_while_let(cx, iter_expr) {
let iterator = snippet(cx, method_args[0].span, "_");
let loop_var = snippet(cx, pat_args[0].span, "_");
span_help_and_lint(cx, WHILE_LET_ON_ITERATOR, expr.span,
"this loop could be written as a `for` loop",
&format!("try\nfor {} in {} {{...}}",
loop_var,
iterator));
}
}
}
}
}
fn check_stmt(&mut self, cx: &LateContext, stmt: &Stmt) {
if let StmtSemi(ref expr, _) = stmt.node {
if let ExprMethodCall(ref method, _, ref args) = expr.node {
if args.len() == 1 && method.node.as_str() == "collect" &&
match_trait_method(cx, expr, &["core", "iter", "Iterator"]) {
span_lint(cx, UNUSED_COLLECT, expr.span, &format!(
"you are collect()ing an iterator and throwing away the result. \
Consider using an explicit for loop to exhaust the iterator"));
}
}
}
}
}
fn check_for_loop(cx: &LateContext, pat: &Pat, arg: &Expr, body: &Expr, expr: &Expr) {
// check for looping over a range and then indexing a sequence with it
// -> the iteratee must be a range literal
if let ExprRange(Some(ref l), _) = arg.node {
// Range should start with `0`
if let ExprLit(ref lit) = l.node {
if let LitInt(0, _) = lit.node {
// the var must be a single name
if let PatIdent(_, ref ident, _) = pat.node {
let mut visitor = VarVisitor { cx: cx, var: ident.node.name,
indexed: HashSet::new(), nonindex: false };
walk_expr(&mut visitor, body);
// linting condition: we only indexed one variable
if visitor.indexed.len() == 1 {
let indexed = visitor.indexed.into_iter().next().expect(
"Len was nonzero, but no contents found");
if visitor.nonindex {
span_lint(cx, NEEDLESS_RANGE_LOOP, expr.span, &format!(
"the loop variable `{}` is used to index `{}`. Consider using \
`for ({}, item) in {}.iter().enumerate()` or similar iterators",
ident.node.name, indexed, ident.node.name, indexed));
} else {
span_lint(cx, NEEDLESS_RANGE_LOOP, expr.span, &format!(
"the loop variable `{}` is only used to index `{}`. \
Consider using `for item in &{}` or similar iterators",
ident.node.name, indexed, indexed));
}
}
}
}
}
}
// if this for loop is iterating over a two-sided range...
if let ExprRange(Some(ref start_expr), Some(ref stop_expr)) = arg.node {
// ...and both sides are compile-time constant integers...
if let Some(start_idx @ Constant::ConstantInt(..)) = constant_simple(start_expr) {
if let Some(stop_idx @ Constant::ConstantInt(..)) = constant_simple(stop_expr) {
// ...and the start index is greater than the stop index,
// this loop will never run. This is often confusing for developers
// who think that this will iterate from the larger value to the
// smaller value.
if start_idx > stop_idx {
span_help_and_lint(cx, REVERSE_RANGE_LOOP, expr.span,
"this range is empty so this for loop will never run",
&format!("Consider using `({}..{}).rev()` if you are attempting to \
iterate over this range in reverse", stop_idx, start_idx));
} else if start_idx == stop_idx {
// if they are equal, it's also problematic - this loop
// will never run.
span_lint(cx, REVERSE_RANGE_LOOP, expr.span,
"this range is empty so this for loop will never run");
}
}
}
}
if let ExprMethodCall(ref method, _, ref args) = arg.node {
// just the receiver, no arguments
if args.len() == 1 {
let method_name = method.node;
// check for looping over x.iter() or x.iter_mut(), could use &x or &mut x
if method_name.as_str() == "iter" || method_name.as_str() == "iter_mut" {
if is_ref_iterable_type(cx, &args[0]) {
let object = snippet(cx, args[0].span, "_");
span_lint(cx, EXPLICIT_ITER_LOOP, expr.span, &format!(
"it is more idiomatic to loop over `&{}{}` instead of `{}.{}()`",
if method_name.as_str() == "iter_mut" { "mut " } else { "" },
object, object, method_name));
}
}
// check for looping over Iterator::next() which is not what you want
else if method_name.as_str() == "next" &&
match_trait_method(cx, arg, &["core", "iter", "Iterator"]) {
span_lint(cx, ITER_NEXT_LOOP, expr.span,
"you are iterating over `Iterator::next()` which is an Option; \
this will compile but is probably not what you want");
}
}
}
// Look for variables that are incremented once per loop iteration.
let mut visitor = IncrementVisitor { cx: cx, states: HashMap::new(), depth: 0, done: false };
walk_expr(&mut visitor, body);
// For each candidate, check the parent block to see if
// it's initialized to zero at the start of the loop.
let map = &cx.tcx.map;
let parent_scope = map.get_enclosing_scope(expr.id).and_then(|id| map.get_enclosing_scope(id) );
if let Some(parent_id) = parent_scope {
if let NodeBlock(block) = map.get(parent_id) {
for (id, _) in visitor.states.iter().filter( |&(_,v)| *v == VarState::IncrOnce) {
let mut visitor2 = InitializeVisitor { cx: cx, end_expr: expr, var_id: id.clone(),
state: VarState::IncrOnce, name: None,
depth: 0,
past_loop: false };
walk_block(&mut visitor2, block);
if visitor2.state == VarState::Warn {
if let Some(name) = visitor2.name {
span_lint(cx, EXPLICIT_COUNTER_LOOP, expr.span,
&format!("the variable `{0}` is used as a loop counter. Consider \
using `for ({0}, item) in {1}.enumerate()` \
or similar iterators",
name, snippet(cx, arg.span, "_")));
}
}
}
}
}
}
/// Recover the essential nodes of a desugared for loop:
/// `for pat in arg { body }` becomes `(pat, arg, body)`.
fn recover_for_loop(expr: &Expr) -> Option<(&Pat, &Expr, &Expr)> {
if_let_chain! {
[
let ExprMatch(ref iterexpr, ref arms, _) = expr.node,
let ExprCall(_, ref iterargs) = iterexpr.node,
iterargs.len() == 1 && arms.len() == 1 && arms[0].guard.is_none(),
let ExprLoop(ref block, _) = arms[0].body.node,
block.stmts.is_empty(),
let Some(ref loopexpr) = block.expr,
let ExprMatch(_, ref innerarms, MatchSource::ForLoopDesugar) = loopexpr.node,
innerarms.len() == 2 && innerarms[0].pats.len() == 1,
let PatEnum(_, Some(ref somepats)) = innerarms[0].pats[0].node,
somepats.len() == 1
], {
return Some((&somepats[0],
&iterargs[0],
&innerarms[0].body));
}
}
None
}
struct VarVisitor<'v, 't: 'v> {
cx: &'v LateContext<'v, 't>, // context reference
var: Name, // var name to look for as index
indexed: HashSet<Name>, // indexed variables
nonindex: bool, // has the var been used otherwise?
}
impl<'v, 't> Visitor<'v> for VarVisitor<'v, 't> {
fn visit_expr(&mut self, expr: &'v Expr) {
if let ExprPath(None, ref path) = expr.node {
if path.segments.len() == 1 && path.segments[0].identifier.name == self.var {
// we are referencing our variable! now check if it's as an index
if_let_chain! {
[
let Some(parexpr) = get_parent_expr(self.cx, expr),
let ExprIndex(ref seqexpr, _) = parexpr.node,
let ExprPath(None, ref seqvar) = seqexpr.node,
seqvar.segments.len() == 1
], {
self.indexed.insert(seqvar.segments[0].identifier.name);
return; // no need to walk further
}
}
// we are not indexing anything, record that
self.nonindex = true;
return;
}
}
walk_expr(self, expr);
}
}
fn is_iterator_used_after_while_let(cx: &LateContext, iter_expr: &Expr) -> bool {
let def_id = match var_def_id(cx, iter_expr) {
Some(id) => id,
None => return false
};
let mut visitor = VarUsedAfterLoopVisitor {
cx: cx,
def_id: def_id,
iter_expr_id: iter_expr.id,
past_while_let: false,
var_used_after_while_let: false
};
if let Some(enclosing_block) = get_enclosing_block(cx, def_id) {
walk_block(&mut visitor, enclosing_block);
}
visitor.var_used_after_while_let
}
struct VarUsedAfterLoopVisitor<'v, 't: 'v> {
cx: &'v LateContext<'v, 't>,
def_id: NodeId,
iter_expr_id: NodeId,
past_while_let: bool,
var_used_after_while_let: bool
}
impl <'v, 't> Visitor<'v> for VarUsedAfterLoopVisitor<'v, 't> {
fn visit_expr(&mut self, expr: &'v Expr) {
if self.past_while_let {
if Some(self.def_id) == var_def_id(self.cx, expr) {
self.var_used_after_while_let = true;
}
} else if self.iter_expr_id == expr.id {
self.past_while_let = true;
}
walk_expr(self, expr);
}
}
/// Return true if the type of expr is one that provides IntoIterator impls
/// for &T and &mut T, such as Vec.
fn is_ref_iterable_type(cx: &LateContext, e: &Expr) -> bool {
// no walk_ptrs_ty: calling iter() on a reference can make sense because it
// will allow further borrows afterwards
let ty = cx.tcx.expr_ty(e);
is_iterable_array(ty) ||
match_type(cx, ty, &VEC_PATH) ||
match_type(cx, ty, &LL_PATH) ||
match_type(cx, ty, &["std", "collections", "hash", "map", "HashMap"]) ||
match_type(cx, ty, &["std", "collections", "hash", "set", "HashSet"]) ||
match_type(cx, ty, &["collections", "vec_deque", "VecDeque"]) ||
match_type(cx, ty, &["collections", "binary_heap", "BinaryHeap"]) ||
match_type(cx, ty, &["collections", "btree", "map", "BTreeMap"]) ||
match_type(cx, ty, &["collections", "btree", "set", "BTreeSet"])
}
fn is_iterable_array(ty: ty::Ty) -> bool {
// IntoIterator is currently only implemented for array sizes <= 32 in rustc
match ty.sty {
ty::TyArray(_, 0...32) => true,
_ => false
}
}
/// If a block begins with a statement (possibly a `let` binding) and has an expression, return it.
fn extract_expr_from_first_stmt(block: &Block) -> Option<&Expr> {
if block.stmts.is_empty() { return None; }
if let StmtDecl(ref decl, _) = block.stmts[0].node {
if let DeclLocal(ref local) = decl.node {
if let Some(ref expr) = local.init { Some(expr) } else { None }
} else { None }
} else { None }
}
/// If a block begins with an expression (with or without semicolon), return it.
fn extract_first_expr(block: &Block) -> Option<&Expr> {
match block.expr {
Some(ref expr) => Some(expr),
None if !block.stmts.is_empty() => match block.stmts[0].node {
StmtExpr(ref expr, _) | StmtSemi(ref expr, _) => Some(expr),
_ => None,
},
_ => None,
}
}
/// Return true if expr contains a single break expr (maybe within a block).
fn is_break_expr(expr: &Expr) -> bool {
match expr.node {
ExprBreak(None) => true,
// there won't be a `let <pat> = break` and so we can safely ignore the StmtDecl case
ExprBlock(ref b) => match extract_first_expr(b) {
Some(ref subexpr) => is_break_expr(subexpr),
None => false,
},
_ => false,
}
}
// To trigger the EXPLICIT_COUNTER_LOOP lint, a variable must be
// incremented exactly once in the loop body, and initialized to zero
// at the start of the loop.
#[derive(PartialEq)]
enum VarState {
Initial, // Not examined yet
IncrOnce, // Incremented exactly once, may be a loop counter
Declared, // Declared but not (yet) initialized to zero
Warn,
DontWarn
}
// Scan a for loop for variables that are incremented exactly once.
struct IncrementVisitor<'v, 't: 'v> {
cx: &'v LateContext<'v, 't>, // context reference
states: HashMap<NodeId, VarState>, // incremented variables
depth: u32, // depth of conditional expressions
done: bool
}
impl<'v, 't> Visitor<'v> for IncrementVisitor<'v, 't> {
fn visit_expr(&mut self, expr: &'v Expr) {
if self.done {
return;
}
// If node is a variable
if let Some(def_id) = var_def_id(self.cx, expr) {
if let Some(parent) = get_parent_expr(self.cx, expr) {
let state = self.states.entry(def_id).or_insert(VarState::Initial);
match parent.node {
ExprAssignOp(op, ref lhs, ref rhs) =>
if lhs.id == expr.id {
if op.node == BiAdd && is_integer_literal(rhs, 1) {
*state = match *state {
VarState::Initial if self.depth == 0 => VarState::IncrOnce,
_ => VarState::DontWarn
};
}
else {
// Assigned some other value
*state = VarState::DontWarn;
}
},
ExprAssign(ref lhs, _) if lhs.id == expr.id => *state = VarState::DontWarn,
ExprAddrOf(mutability,_) if mutability == MutMutable => *state = VarState::DontWarn,
_ => ()
}
}
}
// Give up if there are nested loops
else if is_loop(expr) {
self.states.clear();
self.done = true;
return;
}
// Keep track of whether we're inside a conditional expression
else if is_conditional(expr) {
self.depth += 1;
walk_expr(self, expr);
self.depth -= 1;
return;
}
walk_expr(self, expr);
}
}
// Check whether a variable is initialized to zero at the start of a loop.
struct InitializeVisitor<'v, 't: 'v> {
cx: &'v LateContext<'v, 't>, // context reference
end_expr: &'v Expr, // the for loop. Stop scanning here.
var_id: NodeId,
state: VarState,
name: Option<Name>,
depth: u32, // depth of conditional expressions
past_loop: bool
}
impl<'v, 't> Visitor<'v> for InitializeVisitor<'v, 't> {
fn visit_decl(&mut self, decl: &'v Decl) {
// Look for declarations of the variable
if let DeclLocal(ref local) = decl.node {
if local.pat.id == self.var_id {
if let PatIdent(_, ref ident, _) = local.pat.node {
self.name = Some(ident.node.name);
self.state = if let Some(ref init) = local.init {
if is_integer_literal(init, 0) {
VarState::Warn
} else {
VarState::Declared
}
}
else {
VarState::Declared
}
}
}
}
walk_decl(self, decl);
}
fn visit_expr(&mut self, expr: &'v Expr) {
if self.state == VarState::DontWarn {
return;
}
if expr == self.end_expr {
self.past_loop = true;
return;
}
// No need to visit expressions before the variable is
// declared
if self.state == VarState::IncrOnce {
return;
}
// If node is the desired variable, see how it's used
if var_def_id(self.cx, expr) == Some(self.var_id) {
if let Some(parent) = get_parent_expr(self.cx, expr) {
match parent.node {
ExprAssignOp(_, ref lhs, _) if lhs.id == expr.id => {
self.state = VarState::DontWarn;
}
ExprAssign(ref lhs, ref rhs) if lhs.id == expr.id => {
self.state = if is_integer_literal(rhs, 0) && self.depth == 0 {
VarState::Warn
} else {
VarState::DontWarn
}}
ExprAddrOf(mutability,_) if mutability == MutMutable => self.state = VarState::DontWarn,
_ => ()
}
}
if self.past_loop {
self.state = VarState::DontWarn;
return;
}
}
// If there are other loops between the declaration and the target loop, give up
else if !self.past_loop && is_loop(expr) {
self.state = VarState::DontWarn;
return;
}
// Keep track of whether we're inside a conditional expression
else if is_conditional(expr) {
self.depth += 1;
walk_expr(self, expr);
self.depth -= 1;
return;
}
walk_expr(self, expr);
}
}
fn var_def_id(cx: &LateContext, expr: &Expr) -> Option<NodeId> {
if let Some(path_res) = cx.tcx.def_map.borrow().get(&expr.id) {
if let DefLocal(_, node_id) = path_res.base_def {
return Some(node_id)
}
}
None
}
fn is_loop(expr: &Expr) -> bool {
match expr.node {
ExprLoop(..) | ExprWhile(..) => true,
_ => false
}
}
fn is_conditional(expr: &Expr) -> bool {
match expr.node {
ExprIf(..) | ExprMatch(..) => true,
_ => false
}
}