Positive case of len() -> is_empty()

`s/(?<!\{ self)(?<=\.)len\(\) == 0/is_empty()/g`

Author: tamird

src/compiletest/runtest.rs

@@ -864,7 +864,7 @@ fn check_debugger_output(debugger_run_result: &ProcRes, check_lines: &[String])
                 }
                 first = false;
             }
-            if !failed && rest.len() == 0 {
+            if !failed && rest.is_empty() {
                 i += 1;
             }
             if i == num_check_lines {
@@ -1645,7 +1645,7 @@ fn _arm_push_aux_shared_library(config: &Config, testfile: &Path) {
 // codegen tests (vs. clang)
 
 fn append_suffix_to_stem(p: &Path, suffix: &str) -> PathBuf {
-    if suffix.len() == 0 {
+    if suffix.is_empty() {
         p.to_path_buf()
     } else {
         let mut stem = p.file_stem().unwrap().to_os_string();

src/doc/reference.md

@@ -3783,7 +3783,7 @@ its type parameters are types:
 
 ```ignore
 fn map<A: Clone, B: Clone>(f: |A| -> B, xs: &[A]) -> Vec<B> {
-    if xs.len() == 0 {
+    if xs.is_empty() {
        return vec![];
     }
     let first: B = f(xs[0].clone());

src/libcollections/btree/map.rs

@@ -692,7 +692,7 @@ mod stack {
                         // We've reached the root, so no matter what, we're done. We manually
                         // access the root via the tree itself to avoid creating any dangling
                         // pointers.
-                        if self.map.root.len() == 0 && !self.map.root.is_leaf() {
+                        if self.map.root.is_empty() && !self.map.root.is_leaf() {
                             // We've emptied out the root, so make its only child the new root.
                             // If it's a leaf, we just let it become empty.
                             self.map.depth -= 1;

src/libcollections/btree/node.rs

@@ -1097,7 +1097,7 @@ impl<K, V> Node<K, V> {
     /// When a node has no keys or values and only a single edge, extract that edge.
     pub fn hoist_lone_child(&mut self) {
         // Necessary for correctness, but in a private module
-        debug_assert!(self.len() == 0);
+        debug_assert!(self.is_empty());
         debug_assert!(!self.is_leaf());
 
         unsafe {

src/libcore/slice.rs

@@ -207,7 +207,7 @@ impl<T> SliceExt for [T] {
 
     #[inline]
     fn first(&self) -> Option<&T> {
-        if self.len() == 0 { None } else { Some(&self[0]) }
+        if self.is_empty() { None } else { Some(&self[0]) }
     }
 
     #[inline]
@@ -220,7 +220,7 @@ impl<T> SliceExt for [T] {
 
     #[inline]
     fn last(&self) -> Option<&T> {
-        if self.len() == 0 { None } else { Some(&self[self.len() - 1]) }
+        if self.is_empty() { None } else { Some(&self[self.len() - 1]) }
     }
 
     #[inline]
@@ -305,7 +305,7 @@ impl<T> SliceExt for [T] {
 
     #[inline]
     fn first_mut(&mut self) -> Option<&mut T> {
-        if self.len() == 0 { None } else { Some(&mut self[0]) }
+        if self.is_empty() { None } else { Some(&mut self[0]) }
     }
 
     #[inline]
@@ -1313,7 +1313,7 @@ impl<'a, T> Iterator for Chunks<'a, T> {
 
     #[inline]
     fn next(&mut self) -> Option<&'a [T]> {
-        if self.v.len() == 0 {
+        if self.v.is_empty() {
             None
         } else {
             let chunksz = cmp::min(self.v.len(), self.size);
@@ -1325,7 +1325,7 @@ impl<'a, T> Iterator for Chunks<'a, T> {
 
     #[inline]
     fn size_hint(&self) -> (usize, Option<usize>) {
-        if self.v.len() == 0 {
+        if self.v.is_empty() {
             (0, Some(0))
         } else {
             let n = self.v.len() / self.size;
@@ -1340,7 +1340,7 @@ impl<'a, T> Iterator for Chunks<'a, T> {
 impl<'a, T> DoubleEndedIterator for Chunks<'a, T> {
     #[inline]
     fn next_back(&mut self) -> Option<&'a [T]> {
-        if self.v.len() == 0 {
+        if self.v.is_empty() {
             None
         } else {
             let remainder = self.v.len() % self.size;
@@ -1391,7 +1391,7 @@ impl<'a, T> Iterator for ChunksMut<'a, T> {
 
     #[inline]
     fn next(&mut self) -> Option<&'a mut [T]> {
-        if self.v.len() == 0 {
+        if self.v.is_empty() {
             None
         } else {
             let sz = cmp::min(self.v.len(), self.chunk_size);
@@ -1404,7 +1404,7 @@ impl<'a, T> Iterator for ChunksMut<'a, T> {
 
     #[inline]
     fn size_hint(&self) -> (usize, Option<usize>) {
-        if self.v.len() == 0 {
+        if self.v.is_empty() {
             (0, Some(0))
         } else {
             let n = self.v.len() / self.chunk_size;
@@ -1419,7 +1419,7 @@ impl<'a, T> Iterator for ChunksMut<'a, T> {
 impl<'a, T> DoubleEndedIterator for ChunksMut<'a, T> {
     #[inline]
     fn next_back(&mut self) -> Option<&'a mut [T]> {
-        if self.v.len() == 0 {
+        if self.v.is_empty() {
             None
         } else {
             let remainder = self.v.len() % self.chunk_size;

src/libcore/str/mod.rs

@@ -1000,7 +1000,7 @@ enum OldSearcher {
 impl OldSearcher {
     #[allow(dead_code)]
     fn new(haystack: &[u8], needle: &[u8]) -> OldSearcher {
-        if needle.len() == 0 {
+        if needle.is_empty() {
             // Handle specially
             unimplemented!()
         // FIXME: Tune this.

src/libcore/str/pattern.rs

@@ -406,7 +406,7 @@ fn str_search_step<F, G>(mut m: &mut StrSearcher,
 {
     if m.done {
         SearchStep::Done
-    } else if m.needle.len() == 0 && m.start <= m.end {
+    } else if m.needle.is_empty() && m.start <= m.end {
         // Case for needle == ""
         if m.start == m.end {
             m.done = true;

src/liblog/directive.rs

@@ -45,7 +45,7 @@ pub fn parse_logging_spec(spec: &str) -> (Vec<LogDirective>, Option<String>) {
         return (dirs, None);
     }
     mods.map(|m| { for s in m.split(',') {
-        if s.len() == 0 { continue }
+        if s.is_empty() { continue }
         let mut parts = s.split('=');
         let (log_level, name) = match (parts.next(), parts.next().map(|s| s.trim()), parts.next()) {
             (Some(part0), None, None) => {

src/librustc/metadata/creader.rs

@@ -80,7 +80,7 @@ pub fn validate_crate_name(sess: Option<&Session>, s: &str, sp: Option<Span>) {
             (None, Some(sess)) => sess.err(s),
         }
     };
-    if s.len() == 0 {
+    if s.is_empty() {
         say("crate name must not be empty");
     }
     for c in s.chars() {

src/librustc/metadata/decoder.rs

@@ -767,7 +767,7 @@ pub fn get_enum_variants<'tcx>(intr: Rc<IdentInterner>, cdata: Cmd, id: ast::Nod
                         get_type(cdata, field_ty.id.node, tcx).ty
                     })
                     .collect();
-                let arg_names = if arg_names.len() == 0 { None } else { Some(arg_names) };
+                let arg_names = if arg_names.is_empty() { None } else { Some(arg_names) };
 
                 (None, arg_tys, arg_names)
             }
@@ -1383,7 +1383,7 @@ pub fn get_dylib_dependency_formats(cdata: Cmd)
 
     debug!("found dylib deps: {}", formats.as_str_slice());
     for spec in formats.as_str_slice().split(',') {
-        if spec.len() == 0 { continue }
+        if spec.is_empty() { continue }
         let cnum = spec.split(':').nth(0).unwrap();
         let link = spec.split(':').nth(1).unwrap();
         let cnum: ast::CrateNum = cnum.parse().unwrap();

src/librustc/metadata/encoder.rs

@@ -1751,7 +1751,7 @@ fn encode_codemap(ecx: &EncodeContext, rbml_w: &mut Encoder) {
 
     for filemap in &codemap.files.borrow()[..] {
 
-        if filemap.lines.borrow().len() == 0 || filemap.is_imported() {
+        if filemap.lines.borrow().is_empty() || filemap.is_imported() {
             // No need to export empty filemaps, as they can't contain spans
             // that need translation.
             // Also no need to re-export imported filemaps, as any downstream

src/librustc/metadata/loader.rs

@@ -517,7 +517,7 @@ impl<'a> Context<'a> {
             //                library's metadata sections. In theory we should
             //                read both, but reading dylib metadata is quite
             //                slow.
-            if m.len() == 0 {
+            if m.is_empty() {
                 return None
             } else if m.len() == 1 {
                 return Some(m.into_iter().next().unwrap())

src/librustc/middle/check_match.rs

@@ -239,7 +239,7 @@ fn check_for_bindings_named_the_same_as_variants(cx: &MatchCheckCtxt, pat: &Pat)
                     if let Some(DefLocal(_)) = def {
                         if ty::enum_variants(cx.tcx, def_id).iter().any(|variant|
                             token::get_name(variant.name) == token::get_name(ident.node.name)
-                                && variant.args.len() == 0
+                                && variant.args.is_empty()
                         ) {
                             span_warn!(cx.tcx.sess, p.span, E0170,
                                 "pattern binding `{}` is named the same as one \
@@ -636,19 +636,19 @@ fn is_useful(cx: &MatchCheckCtxt,
              -> Usefulness {
     let &Matrix(ref rows) = matrix;
     debug!("{:?}", matrix);
-    if rows.len() == 0 {
+    if rows.is_empty() {
         return match witness {
             ConstructWitness => UsefulWithWitness(vec!()),
             LeaveOutWitness => Useful
         };
     }
-    if rows[0].len() == 0 {
+    if rows[0].is_empty() {
         return NotUseful;
     }
     assert!(rows.iter().all(|r| r.len() == v.len()));
     let real_pat = match rows.iter().find(|r| (*r)[0].id != DUMMY_NODE_ID) {
         Some(r) => raw_pat(r[0]),
-        None if v.len() == 0 => return NotUseful,
+        None if v.is_empty() => return NotUseful,
         None => v[0]
     };
     let left_ty = if real_pat.id == DUMMY_NODE_ID {

src/librustc/middle/infer/error_reporting.rs

@@ -1240,7 +1240,7 @@ impl<'a, 'tcx> Rebuilder<'a, 'tcx> {
                             let lifetimes =
                                 path.segments.last().unwrap().parameters.lifetimes();
                             let mut insert = Vec::new();
-                            if lifetimes.len() == 0 {
+                            if lifetimes.is_empty() {
                                 let anon = self.cur_anon.get();
                                 for (i, a) in (anon..anon+expected).enumerate() {
                                     if anon_nums.contains(&a) {
@@ -1360,7 +1360,7 @@ impl<'a, 'tcx> Rebuilder<'a, 'tcx> {
 
             ast::AngleBracketedParameters(ref data) => {
                 let mut new_lts = Vec::new();
-                if data.lifetimes.len() == 0 {
+                if data.lifetimes.is_empty() {
                     // traverse once to see if there's a need to insert lifetime
                     let need_insert = (0..expected).any(|i| {
                         indexes.contains(&i)

src/librustc/middle/infer/region_inference/graphviz.rs

@@ -88,7 +88,7 @@ pub fn maybe_print_constraints_for<'a, 'tcx>(region_vars: &RegionVarBindings<'a,
             Err(_) => "/tmp/constraints.node%.dot".to_string(),
         };
 
-        if output_template.len() == 0 {
+        if output_template.is_empty() {
             tcx.sess.bug("empty string provided as RUST_REGION_GRAPH");
         }
 

src/librustc/middle/liveness.rs

@@ -716,7 +716,7 @@ impl<'a, 'tcx> Liveness<'a, 'tcx> {
             None => {
                 // Vanilla 'break' or 'loop', so use the enclosing
                 // loop scope
-                if self.loop_scope.len() == 0 {
+                if self.loop_scope.is_empty() {
                     self.ir.tcx.sess.span_bug(sp, "break outside loop");
                 } else {
                     *self.loop_scope.last().unwrap()
@@ -1586,7 +1586,7 @@ impl<'a, 'tcx> Liveness<'a, 'tcx> {
 
     fn should_warn(&self, var: Variable) -> Option<String> {
         let name = self.ir.variable_name(var);
-        if name.len() == 0 || name.as_bytes()[0] == ('_' as u8) {
+        if name.is_empty() || name.as_bytes()[0] == ('_' as u8) {
             None
         } else {
             Some(name)

src/librustc/middle/subst.rs

@@ -361,7 +361,7 @@ impl<T> VecPerParamSpace<T> {
     pub fn get_self<'a>(&'a self) -> Option<&'a T> {
         let v = self.get_slice(SelfSpace);
         assert!(v.len() <= 1);
-        if v.len() == 0 { None } else { Some(&v[0]) }
+        if v.is_empty() { None } else { Some(&v[0]) }
     }
 
     pub fn len(&self, space: ParamSpace) -> usize {

src/librustc/middle/traits/fulfill.rs

@@ -298,7 +298,7 @@ impl<'tcx> FulfillmentContext<'tcx> {
                self.predicates.len(),
                errors.len());
 
-        if errors.len() == 0 {
+        if errors.is_empty() {
             Ok(())
         } else {
             Err(errors)

src/librustc/middle/traits/select.rs

@@ -687,7 +687,7 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
         // is checked for in `evaluate_stack` (and hence users
         // who might care about this case, like coherence, should use
         // that function).
-        if candidates.len() == 0 {
+        if candidates.is_empty() {
             return Err(Unimplemented);
         }
 
@@ -849,7 +849,7 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
         try!(self.assemble_candidates_from_caller_bounds(stack, &mut candidates));
         // Default implementations have lower priority, so we only
         // consider triggering a default if there is no other impl that can apply.
-        if candidates.vec.len() == 0 {
+        if candidates.vec.is_empty() {
             try!(self.assemble_candidates_from_default_impls(obligation, &mut candidates));
         }
         debug!("candidate list size: {}", candidates.vec.len());

src/librustc/middle/ty.rs

@@ -3078,7 +3078,7 @@ pub fn mk_trait<'tcx>(cx: &ctxt<'tcx>,
 }
 
 fn bound_list_is_sorted(bounds: &[ty::PolyProjectionPredicate]) -> bool {
-    bounds.len() == 0 ||
+    bounds.is_empty() ||
         bounds[1..].iter().enumerate().all(
             |(index, bound)| bounds[index].sort_key() <= bound.sort_key())
 }
@@ -3735,7 +3735,7 @@ pub fn type_contents<'tcx>(cx: &ctxt<'tcx>, ty: Ty<'tcx>) -> TypeContents {
                             if variants.len() == 2 {
                                 let mut data_idx = 0;
 
-                                if variants[0].args.len() == 0 {
+                                if variants[0].args.is_empty() {
                                     data_idx = 1;
                                 }
 
@@ -4248,10 +4248,10 @@ pub fn type_is_c_like_enum(cx: &ctxt, ty: Ty) -> bool {
     match ty.sty {
         ty_enum(did, _) => {
             let variants = enum_variants(cx, did);
-            if variants.len() == 0 {
+            if variants.is_empty() {
                 false
             } else {
-                variants.iter().all(|v| v.args.len() == 0)
+                variants.iter().all(|v| v.args.is_empty())
             }
         }
         _ => false

src/librustc/session/config.rs

@@ -902,7 +902,7 @@ pub fn build_session_options(matches: &getopts::Matches) -> Options {
     };
     output_types.sort();
     output_types.dedup();
-    if output_types.len() == 0 {
+    if output_types.is_empty() {
         output_types.push(OutputTypeExe);
     }
 

src/librustc/util/ppaux.rs

@@ -1270,7 +1270,7 @@ impl<'tcx, T> UserString<'tcx> for ty::Binder<T>
         let names: Vec<_> = names.iter().map(|s| &s[..]).collect();
 
         let value_str = unbound_value.user_string(tcx);
-        if names.len() == 0 {
+        if names.is_empty() {
             value_str
         } else {
             format!("for<{}> {}", names.connect(","), value_str)

src/librustc_driver/driver.rs

@@ -885,9 +885,9 @@ pub fn collect_crate_types(session: &Session,
     // command line, then reuse the empty `base` Vec to hold the types that
     // will be found in crate attributes.
     let mut base = session.opts.crate_types.clone();
-    if base.len() == 0 {
+    if base.is_empty() {
         base.extend(attr_types.into_iter());
-        if base.len() == 0 {
+        if base.is_empty() {
             base.push(link::default_output_for_target(session));
         }
         base.sort();

src/librustc_driver/lib.rs

@@ -427,7 +427,7 @@ impl RustcDefaultCalls {
                         odir: &Option<PathBuf>,
                         ofile: &Option<PathBuf>)
                         -> Compilation {
-        if sess.opts.prints.len() == 0 {
+        if sess.opts.prints.is_empty() {
             return Compilation::Continue;
         }
 

src/librustc_driver/pretty.rs

@@ -672,7 +672,7 @@ fn print_flowgraph<W: Write>(variants: Vec<borrowck_dot::Variant>,
     };
 
     match code {
-        _ if variants.len() == 0 => {
+        _ if variants.is_empty() => {
             let r = dot::render(&lcfg, &mut out);
             return expand_err_details(r);
         }

src/librustc_resolve/build_reduced_graph.rs

@@ -767,7 +767,7 @@ impl<'a, 'b:'a, 'tcx:'b> GraphBuilder<'a, 'b, 'tcx> {
                 f.name
             }).collect::<Vec<_>>();
 
-            if fields.len() == 0 {
+            if fields.is_empty() {
                 child_name_bindings.define_value(def, DUMMY_SP, modifiers);
             }