feat: Add basic reflection

Predicates can now report parameter details that don't show up in
`Display` as well as what children they have.  The expectation is that
this will be used by the solution for #7.

BREAKING CHANGE: `Predicate`s must also implement
`reflection::PredicateReflection`.

Author: epage

src/boolean.rs

@@ -11,6 +11,7 @@
 use std::fmt;
 use std::marker::PhantomData;
 
+use reflection;
 use Predicate;
 
 /// Predicate that combines two `Predicate`s, returning the AND of the results.
@@ -55,6 +56,14 @@ where
     }
 }
 
+impl<M1, M2, Item> reflection::PredicateReflection for AndPredicate<M1, M2, Item>
+where
+    M1: Predicate<Item>,
+    M2: Predicate<Item>,
+    Item: ?Sized,
+{
+}
+
 impl<M1, M2, Item> fmt::Display for AndPredicate<M1, M2, Item>
 where
     M1: Predicate<Item>,
@@ -108,6 +117,14 @@ where
     }
 }
 
+impl<M1, M2, Item> reflection::PredicateReflection for OrPredicate<M1, M2, Item>
+where
+    M1: Predicate<Item>,
+    M2: Predicate<Item>,
+    Item: ?Sized,
+{
+}
+
 impl<M1, M2, Item> fmt::Display for OrPredicate<M1, M2, Item>
 where
     M1: Predicate<Item>,
@@ -156,6 +173,13 @@ where
     }
 }
 
+impl<M, Item> reflection::PredicateReflection for NotPredicate<M, Item>
+where
+    M: Predicate<Item>,
+    Item: ?Sized,
+{
+}
+
 impl<M, Item> fmt::Display for NotPredicate<M, Item>
 where
     M: Predicate<Item>,

src/boxed.rs

@@ -11,6 +11,7 @@
 
 use std::fmt;
 
+use reflection;
 use Predicate;
 
 /// `Predicate` that wraps another `Predicate` as a trait object, allowing
@@ -40,6 +41,12 @@ where
     }
 }
 
+impl<Item> reflection::PredicateReflection for BoxPredicate<Item>
+where
+    Item: ?Sized,
+{
+}
+
 impl<Item> fmt::Display for BoxPredicate<Item>
 where
     Item: ?Sized,

src/constant.rs

@@ -11,6 +11,7 @@
 use std::fmt;
 use std::marker::PhantomData;
 
+use reflection;
 use Predicate;
 
 /// Predicate that always returns a constant (boolean) result.
@@ -28,6 +29,8 @@ impl<Item> Predicate<Item> for BooleanPredicate<Item> {
     }
 }
 
+impl<Item> reflection::PredicateReflection for BooleanPredicate<Item> {}
+
 impl<Item> fmt::Display for BooleanPredicate<Item> {
     fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
         write!(f, "{}", self.retval)

src/core.rs

@@ -6,7 +6,7 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
-use std::fmt;
+use reflection;
 
 /// Trait for generically evaluating a type against a dynamically created
 /// predicate function.
@@ -15,7 +15,7 @@ use std::fmt;
 /// mean that the evaluated item is in some sort of pre-defined set.  This is
 /// different from `Ord` and `Eq` in that an `item` will almost never be the
 /// same type as the implementing `Predicate` type.
-pub trait Predicate<Item: ?Sized>: fmt::Display {
+pub trait Predicate<Item: ?Sized>: reflection::PredicateReflection {
     /// Execute this `Predicate` against `variable`, returning the resulting
     /// boolean.
     fn eval(&self, variable: &Item) -> bool;

src/float/close.rs

@@ -11,6 +11,7 @@ use std::fmt;
 use float_cmp::ApproxEq;
 use float_cmp::Ulps;
 
+use reflection;
 use Predicate;
 
 /// Predicate that ensures two numbers are "close" enough, understanding that rounding errors
@@ -86,6 +87,8 @@ impl Predicate<f64> for IsClosePredicate {
     }
 }
 
+impl reflection::PredicateReflection for IsClosePredicate {}
+
 impl fmt::Display for IsClosePredicate {
     fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
         write!(

src/function.rs

@@ -11,6 +11,7 @@
 use std::fmt;
 use std::marker::PhantomData;
 
+use reflection;
 use Predicate;
 
 /// Predicate that wraps a function over a reference that returns a `bool`.
@@ -60,6 +61,12 @@ where
     }
 }
 
+impl<F, T> reflection::PredicateReflection for FnPredicate<F, T>
+where
+    F: Fn(&T) -> bool,
+{
+}
+
 impl<F, T> fmt::Display for FnPredicate<F, T>
 where
     F: Fn(&T) -> bool,

src/iter.rs

@@ -13,6 +13,7 @@ use std::fmt;
 use std::hash::Hash;
 use std::iter::FromIterator;
 
+use reflection;
 use Predicate;
 
 /// Predicate that returns `true` if `variable` is a member of the pre-defined
@@ -84,6 +85,12 @@ where
     }
 }
 
+impl<T> reflection::PredicateReflection for InPredicate<T>
+where
+    T: PartialEq + fmt::Debug,
+{
+}
+
 impl<T> fmt::Display for InPredicate<T>
 where
     T: PartialEq + fmt::Debug,
@@ -167,6 +174,12 @@ where
     }
 }
 
+impl<T> reflection::PredicateReflection for OrdInPredicate<T>
+where
+    T: Ord + fmt::Debug,
+{
+}
+
 impl<T> fmt::Display for OrdInPredicate<T>
 where
     T: Ord + fmt::Debug,
@@ -211,6 +224,12 @@ where
     }
 }
 
+impl<T> reflection::PredicateReflection for HashableInPredicate<T>
+where
+    T: Hash + Eq + fmt::Debug,
+{
+}
+
 impl<T> fmt::Display for HashableInPredicate<T>
 where
     T: Hash + Eq + fmt::Debug,

src/lib.rs

@@ -69,6 +69,7 @@
 //!         *variable == 42
 //!     }
 //! }
+//! impl predicates::reflection::PredicateReflection for IsTheAnswer {}
 //! impl fmt::Display for IsTheAnswer {
 //!     fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
 //!         write!(f, "var.is_the_answer()")
@@ -101,9 +102,10 @@ extern crate regex;
 pub mod prelude;
 
 mod core;
-pub use core::Predicate;
+pub use core::*;
 mod boxed;
-pub use boxed::BoxPredicate;
+pub use boxed::*;
+pub mod reflection;
 
 // core predicates
 pub mod constant;

src/name.rs

@@ -11,6 +11,7 @@
 use std::fmt;
 use std::marker::PhantomData;
 
+use reflection;
 use Predicate;
 
 /// Augment an existing predicate with a name.
@@ -37,6 +38,13 @@ where
     }
 }
 
+impl<M, Item> reflection::PredicateReflection for NamePredicate<M, Item>
+where
+    M: Predicate<Item>,
+    Item: ?Sized,
+{
+}
+
 impl<M, Item> fmt::Display for NamePredicate<M, Item>
 where
     M: Predicate<Item>,

src/ord.rs

@@ -10,6 +10,7 @@
 
 use std::fmt;
 
+use reflection;
 use Predicate;
 
 #[derive(Clone, Copy, Debug, PartialEq, Eq)]
@@ -65,6 +66,12 @@ where
     }
 }
 
+impl<T> reflection::PredicateReflection for EqPredicate<T>
+where
+    T: fmt::Debug + PartialEq,
+{
+}
+
 impl<T> fmt::Display for EqPredicate<T>
 where
     T: fmt::Debug + PartialEq,
@@ -183,6 +190,12 @@ where
     }
 }
 
+impl<T> reflection::PredicateReflection for OrdPredicate<T>
+where
+    T: fmt::Debug + PartialOrd,
+{
+}
+
 impl<T> fmt::Display for OrdPredicate<T>
 where
     T: fmt::Debug + PartialOrd,

src/path/existence.rs

@@ -9,6 +9,7 @@
 use std::fmt;
 use std::path;
 
+use reflection;
 use Predicate;
 
 /// Predicate that checks if a file is present
@@ -25,6 +26,8 @@ impl Predicate<path::Path> for ExistencePredicate {
     }
 }
 
+impl reflection::PredicateReflection for ExistencePredicate {}
+
 impl fmt::Display for ExistencePredicate {
     fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
         write!(f, "{}(var)", if self.exists { "exists" } else { "missing" })

src/path/fc.rs

@@ -11,6 +11,7 @@ use std::fs;
 use std::io::{self, Read};
 use std::path;
 
+use reflection;
 use Predicate;
 
 fn read_file(path: &path::Path) -> io::Result<Vec<u8>> {
@@ -40,6 +41,12 @@ where
     }
 }
 
+impl<P> reflection::PredicateReflection for FileContentPredicate<P>
+where
+    P: Predicate<[u8]>,
+{
+}
+
 impl<P> fmt::Display for FileContentPredicate<P>
 where
     P: Predicate<[u8]>,

src/path/fs.rs

@@ -11,6 +11,7 @@ use std::fs;
 use std::io::{self, Read};
 use std::path;
 
+use reflection;
 use Predicate;
 
 fn read_file(path: &path::Path) -> io::Result<Vec<u8>> {
@@ -58,6 +59,8 @@ impl Predicate<path::Path> for BinaryFilePredicate {
     }
 }
 
+impl reflection::PredicateReflection for BinaryFilePredicate {}
+
 impl fmt::Display for BinaryFilePredicate {
     fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
         write!(f, "var is {}", self.path.display())
@@ -100,6 +103,8 @@ impl StrFilePredicate {
     }
 }
 
+impl reflection::PredicateReflection for StrFilePredicate {}
+
 impl fmt::Display for StrFilePredicate {
     fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
         write!(f, "var is {}", self.path.display())

src/path/ft.rs

@@ -11,6 +11,7 @@ use std::fs;
 use std::io;
 use std::path;
 
+use reflection;
 use Predicate;
 
 #[derive(Clone, Copy, Debug, PartialEq, Eq)]
@@ -94,6 +95,8 @@ impl Predicate<path::Path> for FileTypePredicate {
     }
 }
 
+impl reflection::PredicateReflection for FileTypePredicate {}
+
 impl fmt::Display for FileTypePredicate {
     fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
         write!(f, "var is {}", self.ft)