std: Stabilize FromStr and parse

This commits adds an associated type to the `FromStr` trait representing an
error payload for parses which do not succeed. The previous return value,
`Option<Self>` did not allow for this form of payload. After the associated type
was added, the following attributes were applied:

* `FromStr` is now stable
* `FromStr::Err` is now stable
* `FromStr::from_str` is now stable
* `StrExt::parse` is now stable
* `FromStr for bool` is now stable
* `FromStr for $float` is now stable
* `FromStr for $integral` is now stable
* Errors returned from stable `FromStr` implementations are stable
* Errors implement `Display` and `Error` (both impl blocks being `#[stable]`)

Closes #15138

Author: alexcrichton

src/compiletest/common.rs

@@ -25,17 +25,18 @@ pub enum Mode {
 }
 
 impl FromStr for Mode {
-    fn from_str(s: &str) -> Option<Mode> {
+    type Err = ();
+    fn from_str(s: &str) -> Result<Mode, ()> {
         match s {
-          "compile-fail" => Some(CompileFail),
-          "run-fail" => Some(RunFail),
-          "run-pass" => Some(RunPass),
-          "run-pass-valgrind" => Some(RunPassValgrind),
-          "pretty" => Some(Pretty),
-          "debuginfo-lldb" => Some(DebugInfoLldb),
-          "debuginfo-gdb" => Some(DebugInfoGdb),
-          "codegen" => Some(Codegen),
-          _ => None,
+          "compile-fail" => Ok(CompileFail),
+          "run-fail" => Ok(RunFail),
+          "run-pass" => Ok(RunPass),
+          "run-pass-valgrind" => Ok(RunPassValgrind),
+          "pretty" => Ok(Pretty),
+          "debuginfo-lldb" => Ok(DebugInfoLldb),
+          "debuginfo-gdb" => Ok(DebugInfoGdb),
+          "codegen" => Ok(Codegen),
+          _ => Err(()),
         }
     }
 }

src/compiletest/compiletest.rs

@@ -35,7 +35,6 @@ extern crate log;
 use std::os;
 use std::old_io;
 use std::old_io::fs;
-use std::str::FromStr;
 use std::thunk::Thunk;
 use getopts::{optopt, optflag, reqopt};
 use common::Config;
@@ -140,9 +139,7 @@ pub fn parse_config(args: Vec<String> ) -> Config {
         build_base: opt_path(matches, "build-base"),
         aux_base: opt_path(matches, "aux-base"),
         stage_id: matches.opt_str("stage-id").unwrap(),
-        mode: FromStr::from_str(matches.opt_str("mode")
-                                       .unwrap()
-                                       .as_slice()).expect("invalid mode"),
+        mode: matches.opt_str("mode").unwrap().parse().ok().expect("invalid mode"),
         run_ignored: matches.opt_present("ignored"),
         filter: filter,
         logfile: matches.opt_str("logfile").map(|s| Path::new(s)),

src/compiletest/header.rs

@@ -352,8 +352,8 @@ pub fn gdb_version_to_int(version_string: &str) -> int {
         panic!("{}", error_string);
     }
 
-    let major: int = components[0].parse().expect(error_string);
-    let minor: int = components[1].parse().expect(error_string);
+    let major: int = components[0].parse().ok().expect(error_string);
+    let minor: int = components[1].parse().ok().expect(error_string);
 
     return major * 1000 + minor;
 }
@@ -363,6 +363,6 @@ pub fn lldb_version_to_int(version_string: &str) -> int {
         "Encountered LLDB version string with unexpected format: {}",
         version_string);
     let error_string = error_string.as_slice();
-    let major: int = version_string.parse().expect(error_string);
+    let major: int = version_string.parse().ok().expect(error_string);
     return major;
 }

src/doc/reference.md

@@ -2994,7 +2994,7 @@ Some examples of call expressions:
 # fn add(x: i32, y: i32) -> i32 { 0 }
 
 let x: i32 = add(1i32, 2i32);
-let pi: Option<f32> = "3.14".parse();
+let pi: Option<f32> = "3.14".parse().ok();
 ```
 
 ### Lambda expressions

src/doc/trpl/guessing-game.md

@@ -400,7 +400,7 @@ a function for that:
 let input = old_io::stdin().read_line()
                        .ok()
                        .expect("Failed to read line");
-let input_num: Option<u32> = input.parse();
+let input_num: Option<u32> = input.parse().ok();
 ```
 
 The `parse` function takes in a `&str` value and converts it into something.
@@ -422,11 +422,13 @@ In this case, we say `x` is a `u32` explicitly, so Rust is able to properly
 tell `random()` what to generate. In a similar fashion, both of these work:
 
 ```{rust,ignore}
-let input_num = "5".parse::<u32>(); // input_num: Option<u32>
-let input_num: Option<u32> = "5".parse(); // input_num: Option<u32>
+let input_num = "5".parse::<u32>().ok(); // input_num: Option<u32>
+let input_num: Option<u32> = "5".parse().ok(); // input_num: Option<u32>
 ```
 
-Anyway, with us now converting our input to a number, our code looks like this:
+Here we're converting the `Result` returned by `parse` to an `Option` by using
+the `ok` method as well.  Anyway, with us now converting our input to a number,
+our code looks like this:
 
 ```{rust,ignore}
 use std::old_io;
@@ -445,7 +447,7 @@ fn main() {
     let input = old_io::stdin().read_line()
                            .ok()
                            .expect("Failed to read line");
-    let input_num: Option<u32> = input.parse();
+    let input_num: Option<u32> = input.parse().ok();
 
     println!("You guessed: {}", input_num);
 
@@ -495,7 +497,7 @@ fn main() {
     let input = old_io::stdin().read_line()
                            .ok()
                            .expect("Failed to read line");
-    let input_num: Option<u32> = input.parse();
+    let input_num: Option<u32> = input.parse().ok();
 
     let num = match input_num {
         Some(num) => num,
@@ -562,7 +564,7 @@ fn main() {
     let input = old_io::stdin().read_line()
                            .ok()
                            .expect("Failed to read line");
-    let input_num: Option<u32> = input.trim().parse();
+    let input_num: Option<u32> = input.trim().parse().ok();
 
     let num = match input_num {
         Some(num) => num,
@@ -638,7 +640,7 @@ fn main() {
         let input = old_io::stdin().read_line()
                                .ok()
                                .expect("Failed to read line");
-        let input_num: Option<u32> = input.trim().parse();
+        let input_num: Option<u32> = input.trim().parse().ok();
 
         let num = match input_num {
             Some(num) => num,
@@ -714,7 +716,7 @@ fn main() {
         let input = old_io::stdin().read_line()
                                .ok()
                                .expect("Failed to read line");
-        let input_num: Option<u32> = input.trim().parse();
+        let input_num: Option<u32> = input.trim().parse().ok();
 
         let num = match input_num {
             Some(num) => num,
@@ -770,7 +772,7 @@ fn main() {
         let input = old_io::stdin().read_line()
                                .ok()
                                .expect("Failed to read line");
-        let input_num: Option<u32> = input.trim().parse();
+        let input_num: Option<u32> = input.trim().parse().ok();
 
         let num = match input_num {
             Some(num) => num,
@@ -847,7 +849,7 @@ fn main() {
         let input = old_io::stdin().read_line()
                                .ok()
                                .expect("Failed to read line");
-        let input_num: Option<u32> = input.trim().parse();
+        let input_num: Option<u32> = input.trim().parse().ok();
 
         let num = match input_num {
             Some(num) => num,

src/libcollections/str.rs

@@ -68,6 +68,7 @@ use core::ops::FullRange;
 #[cfg(not(stage0))]
 use core::ops::RangeFull;
 use core::option::Option::{self, Some, None};
+use core::result::Result;
 use core::slice::AsSlice;
 use core::str as core_str;
 use unicode::str::{UnicodeStr, Utf16Encoder};
@@ -1231,13 +1232,12 @@ pub trait StrExt: Index<RangeFull, Output = str> {
     /// # Example
     ///
     /// ```
-    /// assert_eq!("4".parse::<u32>(), Some(4));
-    /// assert_eq!("j".parse::<u32>(), None);
+    /// assert_eq!("4".parse::<u32>(), Ok(4));
+    /// assert!("j".parse::<u32>().is_err());
     /// ```
     #[inline]
-    #[unstable(feature = "collections",
-               reason = "this method was just created")]
-    fn parse<F: FromStr>(&self) -> Option<F> {
+    #[stable(feature = "rust1", since = "1.0.0")]
+    fn parse<F: FromStr>(&self) -> Result<F, F::Err> {
         core_str::StrExt::parse(&self[])
     }
 

src/libcollections/string.rs

@@ -940,10 +940,12 @@ pub fn as_string<'a>(x: &'a str) -> DerefString<'a> {
     DerefString { x: as_vec(x.as_bytes()) }
 }
 
+#[unstable(feature = "collections", reason = "associated error type may change")]
 impl FromStr for String {
+    type Err = ();
     #[inline]
-    fn from_str(s: &str) -> Option<String> {
-        Some(String::from_str(s))
+    fn from_str(s: &str) -> Result<String, ()> {
+        Ok(String::from_str(s))
     }
 }
 
@@ -1016,7 +1018,7 @@ mod tests {
 
     #[test]
     fn test_from_str() {
-      let owned: Option<::std::string::String> = "string".parse();
+      let owned: Option<::std::string::String> = "string".parse().ok();
       assert_eq!(owned.as_ref().map(|s| s.as_slice()), Some("string"));
     }