auto merge of #9250 : erickt/rust/num, r=erickt

This PR solves one of the pain points with c-style enums. Simplifies writing a fn to convert from an int/uint to an enum. It does this through a `#[deriving(FromPrimitive)]` syntax extension.

Before this is committed though, we need to discuss if `ToPrimitive`/`FromPrimitive` has the right design (cc #4819). I've changed all the `.to_int()` and `from_int()` style functions to return `Option<int>` so we can handle partial functions. For this PR though only enums and `extra::num::bigint::*` take advantage of returning None for unrepresentable values. In the long run it'd be better if `i64.to_i8()` returned `None` if the value was too large, but I'll save this for a future PR.

Closes #3868.

src/test/compile-fail/deriving-primitive.rs

@@ -0,0 +1,34 @@
+// Copyright 2013 The Rust Project Developers. See the COPYRIGHT
+// file at the top-level directory of this distribution and at
+// http://rust-lang.org/COPYRIGHT.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+use std::num::FromPrimitive;
+use std::int;
+
+#[deriving(FromPrimitive)]
+struct A { x: int }
+//~^^ ERROR `FromPrimitive` cannot be derived for structs
+//~^^^ ERROR `FromPrimitive` cannot be derived for structs
+
+#[deriving(FromPrimitive)]
+struct B(int);
+//~^^ ERROR `FromPrimitive` cannot be derived for structs
+//~^^^ ERROR `FromPrimitive` cannot be derived for structs
+
+#[deriving(FromPrimitive)]
+enum C { Foo(int), Bar(uint) }
+//~^^ ERROR `FromPrimitive` cannot be derived for enum variants with arguments
+//~^^^ ERROR `FromPrimitive` cannot be derived for enum variants with arguments
+
+#[deriving(FromPrimitive)]
+enum D { Baz { x: int } }
+//~^^ ERROR `FromPrimitive` cannot be derived for enums with struct variants
+//~^^^ ERROR `FromPrimitive` cannot be derived for enums with struct variants
+
+pub fn main() {}

src/test/run-pass/deriving-primitive.rs

@@ -0,0 +1,37 @@
+// Copyright 2013 The Rust Project Developers. See the COPYRIGHT
+// file at the top-level directory of this distribution and at
+// http://rust-lang.org/COPYRIGHT.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+use std::num::FromPrimitive;
+use std::int;
+
+#[deriving(Eq, FromPrimitive)]
+enum A {
+    Foo = int::max_value,
+    Bar = 1,
+    Baz = 3,
+    Qux,
+}
+
+pub fn main() {
+    let x: Option<A> = FromPrimitive::from_int(int::max_value);
+    assert_eq!(x, Some(Foo));
+
+    let x: Option<A> = FromPrimitive::from_int(1);
+    assert_eq!(x, Some(Bar));
+
+    let x: Option<A> = FromPrimitive::from_int(3);
+    assert_eq!(x, Some(Baz));
+
+    let x: Option<A> = FromPrimitive::from_int(4);
+    assert_eq!(x, Some(Qux));
+
+    let x: Option<A> = FromPrimitive::from_int(5);
+    assert_eq!(x, None);
+}

src/test/run-pass/numeric-method-autoexport.rs

@@ -36,6 +36,6 @@ pub fn main() {
 
 // floats
     // num
-    assert_eq!(10f32.to_int(), 10);
-    assert_eq!(10f64.to_int(), 10);
+    assert_eq!(10f32.to_int().unwrap(), 10);
+    assert_eq!(10f64.to_int().unwrap(), 10);
 }

src/test/run-pass/trait-inheritance-num.rs

@@ -19,7 +19,7 @@ pub trait NumExt: Num + NumCast + Eq + Ord {}
 
 pub trait FloatExt: NumExt + ApproxEq<Self> {}
 
-fn greater_than_one<T:NumExt>(n: &T) -> bool { *n > NumCast::from(1) }
-fn greater_than_one_float<T:FloatExt>(n: &T) -> bool { *n > NumCast::from(1) }
+fn greater_than_one<T:NumExt>(n: &T) -> bool { *n > NumCast::from(1).unwrap() }
+fn greater_than_one_float<T:FloatExt>(n: &T) -> bool { *n > NumCast::from(1).unwrap() }
 
 pub fn main() {}

src/test/run-pass/trait-inheritance-num0.rs

@@ -22,7 +22,7 @@ trait Num {
 pub trait NumExt: Num + NumCast { }
 
 fn greater_than_one<T:NumExt>(n: &T) -> bool {
-    n.gt(&NumCast::from(1))
+    n.gt(&NumCast::from(1).unwrap())
 }
 
 pub fn main() {}

src/test/run-pass/trait-inheritance-num1.rs

@@ -14,7 +14,7 @@ use std::num::NumCast;
 pub trait NumExt: Num + NumCast + Ord { }
 
 fn greater_than_one<T:NumExt>(n: &T) -> bool {
-    *n > NumCast::from(1)
+    *n > NumCast::from(1).unwrap()
 }
 
 pub fn main() {}

src/test/run-pass/trait-inheritance-num3.rs

@@ -16,7 +16,7 @@ pub trait NumExt: Eq + Ord + Num + NumCast {}
 impl NumExt for f32 {}
 
 fn num_eq_one<T:NumExt>(n: T) {
-    println!("{}", n == NumCast::from(1))
+    println!("{}", n == NumCast::from(1).unwrap())
 }
 
 pub fn main() {

src/test/run-pass/trait-inheritance-num5.rs

@@ -17,7 +17,7 @@ impl NumExt for f32 {}
 impl NumExt for int {}
 
 fn num_eq_one<T:NumExt>() -> T {
-    NumCast::from(1)
+    NumCast::from(1).unwrap()
 }
 
 pub fn main() {