Use Try syntax for Option in place of macros or match

Author: mbrubeck

src/liballoc/allocator.rs

@@ -217,14 +217,8 @@ impl Layout {
     /// On arithmetic overflow, returns `None`.
     #[inline]
     pub fn repeat(&self, n: usize) -> Option<(Self, usize)> {
-        let padded_size = match self.size.checked_add(self.padding_needed_for(self.align)) {
-            None => return None,
-            Some(padded_size) => padded_size,
-        };
-        let alloc_size = match padded_size.checked_mul(n) {
-            None => return None,
-            Some(alloc_size) => alloc_size,
-        };
+        let padded_size = self.size.checked_add(self.padding_needed_for(self.align))?;
+        let alloc_size = padded_size.checked_mul(n)?;
 
         // We can assume that `self.align` is a power-of-two that does
         // not exceed 2<sup>31</sup>. Furthermore, `alloc_size` has already been
@@ -246,26 +240,14 @@ impl Layout {
     /// On arithmetic overflow, returns `None`.
     pub fn extend(&self, next: Self) -> Option<(Self, usize)> {
         let new_align = cmp::max(self.align, next.align);
-        let realigned = match Layout::from_size_align(self.size, new_align) {
-            None => return None,
-            Some(l) => l,
-        };
+        let realigned = Layout::from_size_align(self.size, new_align)?;
 
         let pad = realigned.padding_needed_for(next.align);
 
-        let offset = match self.size.checked_add(pad) {
-            None => return None,
-            Some(offset) => offset,
-        };
-        let new_size = match offset.checked_add(next.size) {
-            None => return None,
-            Some(new_size) => new_size,
-        };
+        let offset = self.size.checked_add(pad)?;
+        let new_size = offset.checked_add(next.size)?;
 
-        let layout = match Layout::from_size_align(new_size, new_align) {
-            None => return None,
-            Some(l) => l,
-        };
+        let layout = Layout::from_size_align(new_size, new_align)?;
         Some((layout, offset))
     }
 
@@ -282,11 +264,7 @@ impl Layout {
     ///
     /// On arithmetic overflow, returns `None`.
     pub fn repeat_packed(&self, n: usize) -> Option<Self> {
-        let size = match self.size().checked_mul(n) {
-            None => return None,
-            Some(scaled) => scaled,
-        };
-
+        let size = self.size().checked_mul(n)?;
         Layout::from_size_align(size, self.align)
     }
 
@@ -306,14 +284,8 @@ impl Layout {
     ///
     /// On arithmetic overflow, returns `None`.
     pub fn extend_packed(&self, next: Self) -> Option<(Self, usize)> {
-        let new_size = match self.size().checked_add(next.size()) {
-            None => return None,
-            Some(new_size) => new_size,
-        };
-        let layout = match Layout::from_size_align(new_size, self.align) {
-            None => return None,
-            Some(l) => l,
-        };
+        let new_size = self.size().checked_add(next.size())?;
+        let layout = Layout::from_size_align(new_size, self.align)?;
         Some((layout, self.size()))
     }
 

src/liballoc/btree/set.rs

@@ -1067,21 +1067,15 @@ impl<'a, T: Ord> Iterator for Intersection<'a, T> {
 
     fn next(&mut self) -> Option<&'a T> {
         loop {
-            let o_cmp = match (self.a.peek(), self.b.peek()) {
-                (None, _) => None,
-                (_, None) => None,
-                (Some(a1), Some(b1)) => Some(a1.cmp(b1)),
-            };
-            match o_cmp {
-                None => return None,
-                Some(Less) => {
+            match Ord::cmp(self.a.peek()?, self.b.peek()?) {
+                Less => {
                     self.a.next();
                 }
-                Some(Equal) => {
+                Equal => {
                     self.b.next();
                     return self.a.next();
                 }
-                Some(Greater) => {
+                Greater => {
                     self.b.next();
                 }
             }

src/liballoc/string.rs

@@ -1044,10 +1044,7 @@ impl String {
     #[inline]
     #[stable(feature = "rust1", since = "1.0.0")]
     pub fn pop(&mut self) -> Option<char> {
-        let ch = match self.chars().rev().next() {
-            Some(ch) => ch,
-            None => return None,
-        };
+        let ch = self.chars().rev().next()?;
         let newlen = self.len() - ch.len_utf8();
         unsafe {
             self.vec.set_len(newlen);

src/liballoc/vec.rs

@@ -1423,10 +1423,7 @@ impl<T: PartialEq> Vec<T> {
     /// ```
     #[unstable(feature = "vec_remove_item", reason = "recently added", issue = "40062")]
     pub fn remove_item(&mut self, item: &T) -> Option<T> {
-        let pos = match self.iter().position(|x| *x == *item) {
-            Some(x) => x,
-            None => return None,
-        };
+        let pos = self.iter().position(|x| *x == *item)?;
         Some(self.remove(pos))
     }
 }

src/libcore/str/mod.rs

@@ -494,11 +494,10 @@ fn unwrap_or_0(opt: Option<&u8>) -> u8 {
 #[inline]
 pub fn next_code_point<'a, I: Iterator<Item = &'a u8>>(bytes: &mut I) -> Option<u32> {
     // Decode UTF-8
-    let x = match bytes.next() {
-        None => return None,
-        Some(&next_byte) if next_byte < 128 => return Some(next_byte as u32),
-        Some(&next_byte) => next_byte,
-    };
+    let x = *bytes.next()?;
+    if x < 128 {
+        return Some(x as u32)
+    }
 
     // Multibyte case follows
     // Decode from a byte combination out of: [[[x y] z] w]

src/librustc/hir/map/mod.rs

@@ -978,9 +978,8 @@ impl<'a, 'hir> NodesMatchingSuffix<'a, 'hir> {
         // chain, then returns `None`.
         fn find_first_mod_parent<'a>(map: &'a Map, mut id: NodeId) -> Option<(NodeId, Name)> {
             loop {
-                match map.find(id) {
-                    None => return None,
-                    Some(NodeItem(item)) if item_is_mod(&item) =>
+                match map.find(id)? {
+                    NodeItem(item) if item_is_mod(&item) =>
                         return Some((id, item.name)),
                     _ => {}
                 }

src/librustc/infer/error_reporting/util.rs

@@ -91,10 +91,8 @@ impl<'a, 'gcx, 'tcx> InferCtxt<'a, 'gcx, 'tcx> {
                         .iter()
                         .enumerate()
                         .filter_map(|(index, arg)| {
-                            let ty = match tables.borrow().node_id_to_type_opt(arg.hir_id) {
-                                Some(v) => v,
-                                None => return None, // sometimes the tables are not yet populated
-                            };
+                            // May return None; sometimes the tables are not yet populated.
+                            let ty = tables.borrow().node_id_to_type_opt(arg.hir_id)?;
                             let mut found_anon_region = false;
                             let new_arg_ty = self.tcx
                                 .fold_regions(&ty, &mut false, |r, _| if *r == *anon_region {

src/librustc/ty/util.rs

@@ -439,12 +439,7 @@ impl<'a, 'gcx, 'tcx> TyCtxt<'a, 'gcx, 'tcx> {
             }
         });
 
-        let dtor_did = match dtor_did {
-            Some(dtor) => dtor,
-            None => return None,
-        };
-
-        Some(ty::Destructor { did: dtor_did })
+        Some(ty::Destructor { did: dtor_did? })
     }
 
     /// Return the set of types that are required to be alive in

src/librustc/util/common.rs

@@ -215,24 +215,18 @@ pub fn record_time<T, F>(accu: &Cell<Duration>, f: F) -> T where
     rv
 }
 
-// Like std::macros::try!, but for Option<>.
-#[cfg(unix)]
-macro_rules! option_try(
-    ($e:expr) => (match $e { Some(e) => e, None => return None })
-);
-
 // Memory reporting
 #[cfg(unix)]
 fn get_resident() -> Option<usize> {
     use std::fs::File;
     use std::io::Read;
 
     let field = 1;
-    let mut f = option_try!(File::open("/proc/self/statm").ok());
+    let mut f = File::open("/proc/self/statm").ok()?;
     let mut contents = String::new();
-    option_try!(f.read_to_string(&mut contents).ok());
-    let s = option_try!(contents.split_whitespace().nth(field));
-    let npages = option_try!(s.parse::<usize>().ok());
+    f.read_to_string(&mut contents).ok()?;
+    let s = contents.split_whitespace().nth(field)?;
+    let npages = s.parse::<usize>().ok()?;
     Some(npages * 4096)
 }
 

src/librustc_data_structures/indexed_set.rs

@@ -291,10 +291,8 @@ impl<'a, T: Idx> Iterator for Iter<'a, T> {
                 }
             }
 
-            match self.iter.next() {
-                Some((i, word)) => self.cur = Some((*word, word_bits * i)),
-                None => return None,
-            }
+            let (i, word) = self.iter.next()?;
+            self.cur = Some((*word, word_bits * i));
         }
     }
 }

src/librustc_metadata/creader.rs

@@ -385,10 +385,7 @@ impl<'a> CrateLoader<'a> {
     }
 
     fn load(&mut self, locate_ctxt: &mut locator::Context) -> Option<LoadResult> {
-        let library = match locate_ctxt.maybe_load_library_crate() {
-            Some(lib) => lib,
-            None => return None,
-        };
+        let library = locate_ctxt.maybe_load_library_crate()?;
 
         // In the case that we're loading a crate, but not matching
         // against a hash, we could load a crate which has the same hash

src/librustc_mir/borrow_check/mod.rs

@@ -1982,10 +1982,7 @@ mod prefixes {
     impl<'cx, 'gcx, 'tcx> Iterator for Prefixes<'cx, 'gcx, 'tcx> {
         type Item = &'cx Place<'tcx>;
         fn next(&mut self) -> Option<Self::Item> {
-            let mut cursor = match self.next {
-                None => return None,
-                Some(place) => place,
-            };
+            let mut cursor = self.next?;
 
             // Post-processing `place`: Enqueue any remaining
             // work. Also, `place` may not be a prefix itself, but

src/librustc_trans/back/archive.rs

@@ -120,10 +120,7 @@ impl<'a> ArchiveBuilder<'a> {
         if let Some(ref a) = self.src_archive {
             return a.as_ref()
         }
-        let src = match self.config.src {
-            Some(ref src) => src,
-            None => return None,
-        };
+        let src = self.config.src.as_ref()?;
         self.src_archive = Some(ArchiveRO::open(src).ok());
         self.src_archive.as_ref().unwrap().as_ref()
     }

src/librustc_typeck/check/autoderef.rs

@@ -79,10 +79,8 @@ impl<'a, 'gcx, 'tcx> Iterator for Autoderef<'a, 'gcx, 'tcx> {
         let (kind, new_ty) = if let Some(mt) = self.cur_ty.builtin_deref(false, NoPreference) {
             (AutoderefKind::Builtin, mt.ty)
         } else {
-            match self.overloaded_deref_ty(self.cur_ty) {
-                Some(ty) => (AutoderefKind::Overloaded, ty),
-                _ => return None,
-            }
+            let ty = self.overloaded_deref_ty(self.cur_ty)?;
+            (AutoderefKind::Overloaded, ty)
         };
 
         if new_ty.references_error() {
@@ -108,10 +106,7 @@ impl<'a, 'gcx, 'tcx> Autoderef<'a, 'gcx, 'tcx> {
 
         // <cur_ty as Deref>
         let trait_ref = TraitRef {
-            def_id: match tcx.lang_items().deref_trait() {
-                Some(f) => f,
-                None => return None,
-            },
+            def_id: tcx.lang_items().deref_trait()?,
             substs: tcx.mk_substs_trait(self.cur_ty, &[]),
         };
 

src/librustdoc/html/format.rs

@@ -425,15 +425,13 @@ pub fn href(did: DefId) -> Option<(String, ItemType, Vec<String>)> {
         Some(&(ref fqp, shortty)) => {
             (fqp, shortty, repeat("../").take(loc.len()).collect())
         }
-        None => match cache.external_paths.get(&did) {
-            Some(&(ref fqp, shortty)) => {
-                (fqp, shortty, match cache.extern_locations[&did.krate] {
-                    (.., render::Remote(ref s)) => s.to_string(),
-                    (.., render::Local) => repeat("../").take(loc.len()).collect(),
-                    (.., render::Unknown) => return None,
-                })
-            }
-            None => return None,
+        None => {
+            let &(ref fqp, shortty) = cache.external_paths.get(&did)?;
+            (fqp, shortty, match cache.extern_locations[&did.krate] {
+                (.., render::Remote(ref s)) => s.to_string(),
+                (.., render::Local) => repeat("../").take(loc.len()).collect(),
+                (.., render::Unknown) => return None,
+            })
         }
     };
     for component in &fqp[..fqp.len() - 1] {

src/librustdoc/html/render.rs

@@ -1672,11 +1672,8 @@ impl<'a> Item<'a> {
         let mut path = String::new();
         let (krate, path) = if self.item.def_id.is_local() {
             let path = PathBuf::from(&self.item.source.filename);
-            if let Some(path) = self.cx.shared.local_sources.get(&path) {
-                (&self.cx.shared.layout.krate, path)
-            } else {
-                return None;
-            }
+            let path = self.cx.shared.local_sources.get(&path)?;
+            (&self.cx.shared.layout.krate, path)
         } else {
             // Macros from other libraries get special filenames which we can
             // safely ignore.

src/libserialize/json.rs

@@ -1052,10 +1052,7 @@ impl Json {
     pub fn find_path<'a>(&'a self, keys: &[&str]) -> Option<&'a Json>{
         let mut target = self;
         for key in keys {
-            match target.find(*key) {
-                Some(t) => { target = t; },
-                None => return None
-            }
+            target = target.find(*key)?;
         }
         Some(target)
     }

src/libstd/collections/hash/set.rs

@@ -1152,13 +1152,9 @@ impl<'a, T, S> Iterator for Intersection<'a, T, S>
 
     fn next(&mut self) -> Option<&'a T> {
         loop {
-            match self.iter.next() {
-                None => return None,
-                Some(elt) => {
-                    if self.other.contains(elt) {
-                        return Some(elt);
-                    }
-                }
+            let elt = self.iter.next()?;
+            if self.other.contains(elt) {
+                return Some(elt);
             }
         }
     }
@@ -1202,13 +1198,9 @@ impl<'a, T, S> Iterator for Difference<'a, T, S>
 
     fn next(&mut self) -> Option<&'a T> {
         loop {
-            match self.iter.next() {
-                None => return None,
-                Some(elt) => {
-                    if !self.other.contains(elt) {
-                        return Some(elt);
-                    }
-                }
+            let elt = self.iter.next()?;
+            if !self.other.contains(elt) {
+                return Some(elt);
             }
         }
     }

src/libstd/io/mod.rs

@@ -2019,10 +2019,9 @@ impl<R: Read> Iterator for Chars<R> {
     type Item = result::Result<char, CharsError>;
 
     fn next(&mut self) -> Option<result::Result<char, CharsError>> {
-        let first_byte = match read_one_byte(&mut self.inner) {
-            None => return None,
-            Some(Ok(b)) => b,
-            Some(Err(e)) => return Some(Err(CharsError::Other(e))),
+        let first_byte = match read_one_byte(&mut self.inner)? {
+            Ok(b) => b,
+            Err(e) => return Some(Err(CharsError::Other(e))),
         };
         let width = core_str::utf8_char_width(first_byte);
         if width == 1 { return Some(Ok(first_byte as char)) }

src/libstd/net/parser.rs

@@ -170,11 +170,7 @@ impl<'a> Parser<'a> {
                 return None;
             }
 
-            let octet = self.read_number(10, 3, 0x100).map(|n| n as u8);
-            match octet {
-                Some(d) => bs[i] = d,
-                None => return None,
-            };
+            bs[i] = self.read_number(10, 3, 0x100).map(|n| n as u8)?;
             i += 1;
         }
         Some(Ipv4Addr::new(bs[0], bs[1], bs[2], bs[3]))