Auto merge of #32390 - japaric:untry, r=pnkfelix

convert 99.9% of `try!`s to `?`s

The first commit is an automated conversion using the [untry] tool and the following command:

```
$ find -name '*.rs' -type f | xargs untry
```

at the root of the Rust repo.

[untry]: https://github.com/japaric/untry

cc @rust-lang/lang @alexcrichton @brson

Author: bors

Diff for: src/compiletest/compiletest.rs

@@ -15,6 +15,7 @@
 #![feature(rustc_private)]
 #![feature(str_char)]
 #![feature(test)]
+#![feature(question_mark)]
 
 #![deny(warnings)]
 
@@ -280,16 +281,16 @@ fn collect_tests_from_dir(config: &Config,
                           -> io::Result<()> {
     // Ignore directories that contain a file
     // `compiletest-ignore-dir`.
-    for file in try!(fs::read_dir(dir)) {
-        let file = try!(file);
+    for file in fs::read_dir(dir)? {
+        let file = file?;
         if file.file_name() == *"compiletest-ignore-dir" {
             return Ok(());
         }
     }
 
-    let dirs = try!(fs::read_dir(dir));
+    let dirs = fs::read_dir(dir)?;
     for file in dirs {
-        let file = try!(file);
+        let file = file?;
         let file_path = file.path();
         debug!("inspecting file {:?}", file_path.display());
         if is_test(config, &file_path) {
@@ -310,11 +311,11 @@ fn collect_tests_from_dir(config: &Config,
             tests.push(make_test(config, &paths))
         } else if file_path.is_dir() {
             let relative_file_path = relative_dir_path.join(file.file_name());
-            try!(collect_tests_from_dir(config,
-                                        base,
-                                        &file_path,
-                                        &relative_file_path,
-                                        tests));
+            collect_tests_from_dir(config,
+                                   base,
+                                   &file_path,
+                                   &relative_file_path,
+                                   tests)?;
         }
     }
     Ok(())

Diff for: src/libcore/fmt/builders.rs

@@ -29,7 +29,7 @@ impl<'a, 'b: 'a> fmt::Write for PadAdapter<'a, 'b> {
     fn write_str(&mut self, mut s: &str) -> fmt::Result {
         while !s.is_empty() {
             if self.on_newline {
-                try!(self.fmt.write_str("    "));
+                self.fmt.write_str("    ")?;
             }
 
             let split = match s.find('\n') {
@@ -42,7 +42,7 @@ impl<'a, 'b: 'a> fmt::Write for PadAdapter<'a, 'b> {
                     s.len()
                 }
             };
-            try!(self.fmt.write_str(&s[..split]));
+            self.fmt.write_str(&s[..split])?;
             s = &s[split..];
         }
 
@@ -169,10 +169,10 @@ impl<'a, 'b: 'a> DebugTuple<'a, 'b> {
         if self.fields > 0 {
             self.result = self.result.and_then(|_| {
                 if self.is_pretty() {
-                    try!(self.fmt.write_str("\n"));
+                    self.fmt.write_str("\n")?;
                 }
                 if self.fields == 1 && self.empty_name {
-                    try!(self.fmt.write_str(","));
+                    self.fmt.write_str(",")?;
                 }
                 self.fmt.write_str(")")
             });

Diff for: src/libcore/fmt/mod.rs

@@ -795,24 +795,24 @@ pub fn write(output: &mut Write, args: Arguments) -> Result {
         None => {
             // We can use default formatting parameters for all arguments.
             for (arg, piece) in args.args.iter().zip(pieces.by_ref()) {
-                try!(formatter.buf.write_str(*piece));
-                try!((arg.formatter)(arg.value, &mut formatter));
+                formatter.buf.write_str(*piece)?;
+                (arg.formatter)(arg.value, &mut formatter)?;
             }
         }
         Some(fmt) => {
             // Every spec has a corresponding argument that is preceded by
             // a string piece.
             for (arg, piece) in fmt.iter().zip(pieces.by_ref()) {
-                try!(formatter.buf.write_str(*piece));
-                try!(formatter.run(arg));
+                formatter.buf.write_str(*piece)?;
+                formatter.run(arg)?;
             }
         }
     }
 
     // There can be only one trailing string piece left.
     match pieces.next() {
         Some(piece) => {
-            try!(formatter.buf.write_str(*piece));
+            formatter.buf.write_str(*piece)?;
         }
         None => {}
     }
@@ -897,9 +897,9 @@ impl<'a> Formatter<'a> {
         // Writes the sign if it exists, and then the prefix if it was requested
         let write_prefix = |f: &mut Formatter| {
             if let Some(c) = sign {
-                try!(f.buf.write_str(unsafe {
+                f.buf.write_str(unsafe {
                     str::from_utf8_unchecked(c.encode_utf8().as_slice())
-                }));
+                })?;
             }
             if prefixed { f.buf.write_str(prefix) }
             else { Ok(()) }
@@ -910,26 +910,26 @@ impl<'a> Formatter<'a> {
             // If there's no minimum length requirements then we can just
             // write the bytes.
             None => {
-                try!(write_prefix(self)); self.buf.write_str(buf)
+                write_prefix(self)?; self.buf.write_str(buf)
             }
             // Check if we're over the minimum width, if so then we can also
             // just write the bytes.
             Some(min) if width >= min => {
-                try!(write_prefix(self)); self.buf.write_str(buf)
+                write_prefix(self)?; self.buf.write_str(buf)
             }
             // The sign and prefix goes before the padding if the fill character
             // is zero
             Some(min) if self.sign_aware_zero_pad() => {
                 self.fill = '0';
-                try!(write_prefix(self));
+                write_prefix(self)?;
                 self.with_padding(min - width, rt::v1::Alignment::Right, |f| {
                     f.buf.write_str(buf)
                 })
             }
             // Otherwise, the sign and prefix goes after the padding
             Some(min) => {
                 self.with_padding(min - width, rt::v1::Alignment::Right, |f| {
-                    try!(write_prefix(f)); f.buf.write_str(buf)
+                    write_prefix(f)?; f.buf.write_str(buf)
                 })
             }
         }
@@ -1008,13 +1008,13 @@ impl<'a> Formatter<'a> {
         };
 
         for _ in 0..pre_pad {
-            try!(self.buf.write_str(fill));
+            self.buf.write_str(fill)?;
         }
 
-        try!(f(self));
+        f(self)?;
 
         for _ in 0..post_pad {
-            try!(self.buf.write_str(fill));
+            self.buf.write_str(fill)?;
         }
 
         Ok(())
@@ -1033,7 +1033,7 @@ impl<'a> Formatter<'a> {
             if self.sign_aware_zero_pad() {
                 // a sign always goes first
                 let sign = unsafe { str::from_utf8_unchecked(formatted.sign) };
-                try!(self.buf.write_str(sign));
+                self.buf.write_str(sign)?;
 
                 // remove the sign from the formatted parts
                 formatted.sign = b"";
@@ -1065,19 +1065,19 @@ impl<'a> Formatter<'a> {
         }
 
         if !formatted.sign.is_empty() {
-            try!(write_bytes(self.buf, formatted.sign));
+            write_bytes(self.buf, formatted.sign)?;
         }
         for part in formatted.parts {
             match *part {
                 flt2dec::Part::Zero(mut nzeroes) => {
                     const ZEROES: &'static str = // 64 zeroes
                         "0000000000000000000000000000000000000000000000000000000000000000";
                     while nzeroes > ZEROES.len() {
-                        try!(self.buf.write_str(ZEROES));
+                        self.buf.write_str(ZEROES)?;
                         nzeroes -= ZEROES.len();
                     }
                     if nzeroes > 0 {
-                        try!(self.buf.write_str(&ZEROES[..nzeroes]));
+                        self.buf.write_str(&ZEROES[..nzeroes])?;
                     }
                 }
                 flt2dec::Part::Num(mut v) => {
@@ -1087,10 +1087,10 @@ impl<'a> Formatter<'a> {
                         *c = b'0' + (v % 10) as u8;
                         v /= 10;
                     }
-                    try!(write_bytes(self.buf, &s[..len]));
+                    write_bytes(self.buf, &s[..len])?;
                 }
                 flt2dec::Part::Copy(buf) => {
-                    try!(write_bytes(self.buf, buf));
+                    write_bytes(self.buf, buf)?;
                 }
             }
         }
@@ -1349,20 +1349,20 @@ impl Display for bool {
 #[stable(feature = "rust1", since = "1.0.0")]
 impl Debug for str {
     fn fmt(&self, f: &mut Formatter) -> Result {
-        try!(f.write_char('"'));
+        f.write_char('"')?;
         let mut from = 0;
         for (i, c) in self.char_indices() {
             let esc = c.escape_default();
             // If char needs escaping, flush backlog so far and write, else skip
             if esc.size_hint() != (1, Some(1)) {
-                try!(f.write_str(&self[from..i]));
+                f.write_str(&self[from..i])?;
                 for c in esc {
-                    try!(f.write_char(c));
+                    f.write_char(c)?;
                 }
                 from = i + c.len_utf8();
             }
         }
-        try!(f.write_str(&self[from..]));
+        f.write_str(&self[from..])?;
         f.write_char('"')
     }
 }
@@ -1377,9 +1377,9 @@ impl Display for str {
 #[stable(feature = "rust1", since = "1.0.0")]
 impl Debug for char {
     fn fmt(&self, f: &mut Formatter) -> Result {
-        try!(f.write_char('\''));
+        f.write_char('\'')?;
         for c in self.escape_default() {
-            try!(f.write_char(c))
+            f.write_char(c)?
         }
         f.write_char('\'')
     }

Diff for: src/libcore/lib.rs

@@ -77,6 +77,7 @@
 #![feature(rustc_attrs)]
 #![feature(staged_api)]
 #![feature(unboxed_closures)]
+#![feature(question_mark)]
 
 #[macro_use]
 mod macros;

Diff for: src/libcore/num/dec2flt/mod.rs

@@ -214,7 +214,7 @@ fn dec2flt<T: RawFloat>(s: &str) -> Result<T, ParseFloatError> {
     }
     let (sign, s) = extract_sign(s);
     let flt = match parse_decimal(s) {
-        ParseResult::Valid(decimal) => try!(convert(decimal)),
+        ParseResult::Valid(decimal) => convert(decimal)?,
         ParseResult::ShortcutToInf => T::infinity(),
         ParseResult::ShortcutToZero => T::zero(),
         ParseResult::Invalid => match s {

Diff for: src/libcore/str/mod.rs

@@ -240,7 +240,7 @@ impl Utf8Error {
 /// ```
 #[stable(feature = "rust1", since = "1.0.0")]
 pub fn from_utf8(v: &[u8]) -> Result<&str, Utf8Error> {
-    try!(run_utf8_validation(v));
+    run_utf8_validation(v)?;
     Ok(unsafe { from_utf8_unchecked(v) })
 }
 

Diff for: src/libgraphviz/lib.rs

@@ -295,6 +295,7 @@
 #![cfg_attr(not(stage0), deny(warnings))]
 
 #![feature(str_escape)]
+#![feature(question_mark)]
 
 use self::LabelText::*;
 
@@ -662,7 +663,7 @@ pub fn render_opts<'a, N, E, G, W>(g: &'a G,
 {
     fn writeln<W: Write>(w: &mut W, arg: &[&str]) -> io::Result<()> {
         for &s in arg {
-            try!(w.write_all(s.as_bytes()));
+            w.write_all(s.as_bytes())?;
         }
         write!(w, "\n")
     }
@@ -671,9 +672,9 @@ pub fn render_opts<'a, N, E, G, W>(g: &'a G,
         w.write_all(b"    ")
     }
 
-    try!(writeln(w, &["digraph ", g.graph_id().as_slice(), " {"]));
+    writeln(w, &["digraph ", g.graph_id().as_slice(), " {"])?;
     for n in g.nodes().iter() {
-        try!(indent(w));
+        indent(w)?;
         let id = g.node_id(n);
 
         let escaped = &g.node_label(n).to_dot_string();
@@ -702,12 +703,12 @@ pub fn render_opts<'a, N, E, G, W>(g: &'a G,
         }
 
         text.push(";");
-        try!(writeln(w, &text));
+        writeln(w, &text)?;
     }
 
     for e in g.edges().iter() {
         let escaped_label = &g.edge_label(e).to_dot_string();
-        try!(indent(w));
+        indent(w)?;
         let source = g.source(e);
         let target = g.target(e);
         let source_id = g.node_id(&source);
@@ -729,7 +730,7 @@ pub fn render_opts<'a, N, E, G, W>(g: &'a G,
         }
 
         text.push(";");
-        try!(writeln(w, &text));
+        writeln(w, &text)?;
     }
 
     writeln(w, &["}"])
@@ -959,7 +960,7 @@ mod tests {
         let mut writer = Vec::new();
         render(&g, &mut writer).unwrap();
         let mut s = String::new();
-        try!(Read::read_to_string(&mut &*writer, &mut s));
+        Read::read_to_string(&mut &*writer, &mut s)?;
         Ok(s)
     }