Implement "method matching". Similar to trait matching, but with the twist that we

have to take the transformed self type into account, and allow for coercion between
the receiver and the actual type declared on the impl.

Author: nikomatsakis

src/librustc/middle/traits/doc.rs

@@ -272,4 +272,11 @@ nested obligation `int : Bar<U>` to find out that `U=uint`.
 It would be good to only do *just as much* nested resolution as
 necessary. Currently, though, we just do a full resolution.
 
+## Method matching
+
+Method dispach follows a slightly different path than normal trait
+selection. This is because it must account for the transformed self
+type of the receiver and various other complications. The procedure is
+described in `select.rs` in the "METHOD MATCHING" section.
+
 */

src/librustc/middle/traits/mod.rs

@@ -24,6 +24,8 @@ use syntax::codemap::{Span, DUMMY_SP};
 pub use self::fulfill::FulfillmentContext;
 pub use self::select::SelectionContext;
 pub use self::select::SelectionCache;
+pub use self::select::{MethodMatchResult, MethodMatched, MethodAmbiguous, MethodDidNotMatch};
+pub use self::select::{MethodMatchedData}; // intentionally don't export variants
 pub use self::util::supertraits;
 pub use self::util::transitive_bounds;
 pub use self::util::Supertraits;
@@ -219,22 +221,6 @@ pub struct VtableParamData {
     pub bound: Rc<ty::TraitRef>,
 }
 
-pub fn evaluate_obligation<'a,'tcx>(infcx: &InferCtxt<'a,'tcx>,
-                                    param_env: &ty::ParameterEnvironment,
-                                    obligation: &Obligation,
-                                    typer: &Typer<'tcx>)
-                                    -> bool
-{
-    /*!
-     * Attempts to resolve the obligation given. Returns `None` if
-     * we are unable to resolve, either because of ambiguity or
-     * due to insufficient inference.
-     */
-
-    let mut selcx = select::SelectionContext::new(infcx, param_env, typer);
-    selcx.evaluate_obligation(obligation)
-}
-
 pub fn select_inherent_impl<'a,'tcx>(infcx: &InferCtxt<'a,'tcx>,
                                      param_env: &ty::ParameterEnvironment,
                                      typer: &Typer<'tcx>,