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.

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>,