rustc: implement fully qualified UFCS expressions.

Author: eddyb

src/librustc_resolve/lib.rs

@@ -61,7 +61,7 @@ use rustc::util::lev_distance::lev_distance;
 use syntax::ast::{Arm, BindByRef, BindByValue, BindingMode, Block, Crate, CrateNum};
 use syntax::ast::{DefId, Expr, ExprAgain, ExprBreak, ExprField};
 use syntax::ast::{ExprClosure, ExprForLoop, ExprLoop, ExprWhile, ExprMethodCall};
-use syntax::ast::{ExprPath, ExprStruct, FnDecl};
+use syntax::ast::{ExprPath, ExprQPath, ExprStruct, FnDecl};
 use syntax::ast::{ForeignItemFn, ForeignItemStatic, Generics};
 use syntax::ast::{Ident, ImplItem, Item, ItemConst, ItemEnum, ItemFn};
 use syntax::ast::{ItemForeignMod, ItemImpl, ItemMac, ItemMod, ItemStatic};
@@ -3169,7 +3169,7 @@ impl<'a, 'tcx> Resolver<'a, 'tcx> {
                     TraitImplementation        => "implement",
                     TraitDerivation            => "derive",
                     TraitObject                => "reference",
-                    TraitQPath                 => "extract an associated type from",
+                    TraitQPath                 => "extract an associated item from",
                 };
 
                 let msg = format!("attempt to {} a nonexistent trait `{}`", usage_str, path_str);
@@ -3565,31 +3565,17 @@ impl<'a, 'tcx> Resolver<'a, 'tcx> {
                     }
                 }
 
-                match result_def {
-                    None => {
-                        match self.resolve_path(ty.id, path, TypeNS, true) {
-                            Some(def) => {
-                                debug!("(resolving type) resolved `{:?}` to \
-                                        type {:?}",
-                                       token::get_ident(path.segments.last().unwrap() .identifier),
-                                       def);
-                                result_def = Some(def);
-                            }
-                            None => {
-                                result_def = None;
-                            }
-                        }
-                    }
-                    Some(_) => {}   // Continue.
+                if let None = result_def {
+                    result_def = self.resolve_path(ty.id, path, TypeNS, true);
                 }
 
                 match result_def {
                     Some(def) => {
                         // Write the result into the def map.
                         debug!("(resolving type) writing resolution for `{}` \
-                                (id {})",
+                                (id {}) = {:?}",
                                self.path_names_to_string(path),
-                               path_id);
+                               path_id, def);
                         self.record_def(path_id, def);
                     }
                     None => {
@@ -3609,6 +3595,12 @@ impl<'a, 'tcx> Resolver<'a, 'tcx> {
             TyQPath(ref qpath) => {
                 self.resolve_type(&*qpath.self_type);
                 self.resolve_trait_reference(ty.id, &*qpath.trait_ref, TraitQPath);
+                for ty in qpath.item_path.parameters.types().into_iter() {
+                    self.resolve_type(&**ty);
+                }
+                for binding in qpath.item_path.parameters.bindings().into_iter() {
+                    self.resolve_type(&*binding.ty);
+                }
             }
 
             TyPolyTraitRef(ref bounds) => {
@@ -4400,15 +4392,25 @@ impl<'a, 'tcx> Resolver<'a, 'tcx> {
             // The interpretation of paths depends on whether the path has
             // multiple elements in it or not.
 
-            ExprPath(ref path) => {
+            ExprPath(_) | ExprQPath(_) => {
+                let mut path_from_qpath;
+                let path = match expr.node {
+                    ExprPath(ref path) => path,
+                    ExprQPath(ref qpath) => {
+                        self.resolve_type(&*qpath.self_type);
+                        self.resolve_trait_reference(expr.id, &*qpath.trait_ref, TraitQPath);
+                        path_from_qpath = qpath.trait_ref.path.clone();
+                        path_from_qpath.segments.push(qpath.item_path.clone());
+                        &path_from_qpath
+                    }
+                    _ => unreachable!()
+                };
                 // This is a local path in the value namespace. Walk through
                 // scopes looking for it.
-
-                let path_name = self.path_names_to_string(path);
-
                 match self.resolve_path(expr.id, path, ValueNS, true) {
                     // Check if struct variant
                     Some((DefVariant(_, _, true), _)) => {
+                        let path_name = self.path_names_to_string(path);
                         self.resolve_error(expr.span,
                                 format!("`{}` is a struct variant name, but \
                                          this expression \
@@ -4423,7 +4425,7 @@ impl<'a, 'tcx> Resolver<'a, 'tcx> {
                     Some(def) => {
                         // Write the result into the def map.
                         debug!("(resolving expr) resolved `{}`",
-                               path_name);
+                               self.path_names_to_string(path));
 
                         self.record_def(expr.id, def);
                     }
@@ -4432,6 +4434,7 @@ impl<'a, 'tcx> Resolver<'a, 'tcx> {
                         // (The pattern matching def_tys where the id is in self.structs
                         // matches on regular structs while excluding tuple- and enum-like
                         // structs, which wouldn't result in this error.)
+                        let path_name = self.path_names_to_string(path);
                         match self.with_no_errors(|this|
                             this.resolve_path(expr.id, path, TypeNS, false)) {
                             Some((DefTy(struct_id, _), _))

src/librustc_trans/save/mod.rs

@@ -767,7 +767,7 @@ impl <'l, 'tcx> DxrVisitor<'l, 'tcx> {
                     span: Span,
                     path: &ast::Path,
                     ref_kind: Option<recorder::Row>) {
-        if generated_code(path.span) {
+        if generated_code(span) {
             return
         }
 
@@ -1307,9 +1307,15 @@ impl<'l, 'tcx, 'v> Visitor<'v> for DxrVisitor<'l, 'tcx> {
                 visit::walk_expr(self, ex);
             },
             ast::ExprPath(ref path) => {
-                self.process_path(ex.id, ex.span, path, None);
+                self.process_path(ex.id, path.span, path, None);
                 visit::walk_path(self, path);
             }
+            ast::ExprQPath(ref qpath) => {
+                let mut path = qpath.trait_ref.path.clone();
+                path.segments.push(qpath.item_path.clone());
+                self.process_path(ex.id, ex.span, &path, None);
+                visit::walk_qpath(self, ex.span, &**qpath);
+            }
             ast::ExprStruct(ref path, ref fields, ref base) =>
                 self.process_struct_lit(ex, path, fields, base),
             ast::ExprMethodCall(_, _, ref args) => self.process_method_call(ex, args),
@@ -1439,7 +1445,7 @@ impl<'l, 'tcx, 'v> Visitor<'v> for DxrVisitor<'l, 'tcx> {
                                           "")
                 }
                 def::DefVariant(..) => {
-                    paths_to_process.push((id, p.span, p.clone(), Some(ref_kind)))
+                    paths_to_process.push((id, p.clone(), Some(ref_kind)))
                 }
                 // FIXME(nrc) what are these doing here?
                 def::DefStatic(_, _) => {}
@@ -1448,8 +1454,8 @@ impl<'l, 'tcx, 'v> Visitor<'v> for DxrVisitor<'l, 'tcx> {
                             *def)
             }
         }
-        for &(id, span, ref path, ref_kind) in paths_to_process.iter() {
-            self.process_path(id, span, path, ref_kind);
+        for &(id, ref path, ref_kind) in paths_to_process.iter() {
+            self.process_path(id, path.span, path, ref_kind);
         }
         self.collecting = false;
         self.collected_paths.clear();

src/librustc_typeck/check/_match.rs

@@ -467,7 +467,7 @@ pub fn check_pat_struct<'a, 'tcx>(pcx: &pat_ctxt<'a, 'tcx>, pat: &ast::Pat,
     };
 
     instantiate_path(pcx.fcx, path, ty::lookup_item_type(tcx, enum_def_id),
-                     def, pat.span, pat.id);
+                     None, def, pat.span, pat.id);
 
     let pat_ty = fcx.node_ty(pat.id);
     demand::eqtype(fcx, pat.span, expected, pat_ty);
@@ -505,7 +505,7 @@ pub fn check_pat_enum<'a, 'tcx>(pcx: &pat_ctxt<'a, 'tcx>, pat: &ast::Pat,
     } else {
         ctor_scheme
     };
-    instantiate_path(pcx.fcx, path, path_scheme, def, pat.span, pat.id);
+    instantiate_path(pcx.fcx, path, path_scheme, None, def, pat.span, pat.id);
 
     let pat_ty = fcx.node_ty(pat.id);
     demand::eqtype(fcx, pat.span, expected, pat_ty);

src/librustc_typeck/check/mod.rs

@@ -3553,10 +3553,25 @@ fn check_expr_with_unifier<'a, 'tcx, F>(fcx: &FnCtxt<'a, 'tcx>,
         };
         fcx.write_ty(id, oprnd_t);
       }
-      ast::ExprPath(ref pth) => {
-          let defn = lookup_def(fcx, pth.span, id);
+      ast::ExprPath(ref path) => {
+          let defn = lookup_def(fcx, path.span, id);
           let pty = type_scheme_for_def(fcx, expr.span, defn);
-          instantiate_path(fcx, pth, pty, defn, expr.span, expr.id);
+          instantiate_path(fcx, path, pty, None, defn, expr.span, expr.id);
+
+          // We always require that the type provided as the value for
+          // a type parameter outlives the moment of instantiation.
+          constrain_path_type_parameters(fcx, expr);
+      }
+      ast::ExprQPath(ref qpath) => {
+          // Require explicit type params for the trait.
+          let self_ty = fcx.to_ty(&*qpath.self_type);
+          astconv::instantiate_trait_ref(fcx, fcx, &*qpath.trait_ref, Some(self_ty), None);
+
+          let defn = lookup_def(fcx, expr.span, id);
+          let pty = type_scheme_for_def(fcx, expr.span, defn);
+          let mut path = qpath.trait_ref.path.clone();
+          path.segments.push(qpath.item_path.clone());
+          instantiate_path(fcx, &path, pty, Some(self_ty), defn, expr.span, expr.id);
 
           // We always require that the type provided as the value for
           // a type parameter outlives the moment of instantiation.
@@ -4619,6 +4634,7 @@ pub fn type_scheme_for_def<'a, 'tcx>(fcx: &FnCtxt<'a, 'tcx>,
 pub fn instantiate_path<'a, 'tcx>(fcx: &FnCtxt<'a, 'tcx>,
                                   path: &ast::Path,
                                   type_scheme: TypeScheme<'tcx>,
+                                  opt_self_ty: Option<Ty<'tcx>>,
                                   def: def::Def,
                                   span: Span,
                                   node_id: ast::NodeId) {
@@ -4776,6 +4792,11 @@ pub fn instantiate_path<'a, 'tcx>(fcx: &FnCtxt<'a, 'tcx>,
             }
         }
     }
+    if let Some(self_ty) = opt_self_ty {
+        // `<T as Trait>::foo` shouldn't have resolved to a `Self`-less item.
+        assert_eq!(type_defs.len(subst::SelfSpace), 1);
+        substs.types.push(subst::SelfSpace, self_ty);
+    }
 
     // Now we have to compare the types that the user *actually*
     // provided against the types that were *expected*. If the user

src/test/compile-fail/ufcs-qpath-missing-params.rs

@@ -0,0 +1,17 @@
+// Copyright 2014 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::borrow::IntoCow;
+
+fn main() {
+    <String as IntoCow>::into_cow("foo".to_string());
+    //~^ ERROR wrong number of type arguments: expected 2, found 0
+}
+

src/test/compile-fail/ufcs-qpath-self-mismatch.rs

@@ -0,0 +1,21 @@
+// Copyright 2014 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::ops::Add;
+
+fn main() {
+    <i32 as Add<u32>>::add(1, 2);
+    //~^ ERROR the trait `core::ops::Add<u32>` is not implemented for the type `i32`
+    <i32 as Add<i32>>::add(1u32, 2);
+    //~^ ERROR mismatched types
+    <i32 as Add<i32>>::add(1, 2u32);
+    //~^ ERROR mismatched types
+}
+

src/test/run-pass/const-polymorphic-paths.rs

@@ -10,9 +10,11 @@
 
 #![feature(macro_rules)]
 
+use std::borrow::{Cow, IntoCow};
 use std::collections::Bitv;
 use std::default::Default;
 use std::iter::FromIterator;
+use std::ops::Add;
 use std::option::IntoIter as OptionIter;
 use std::rand::Rand;
 use std::rand::XorShiftRng as DummyRng;
@@ -28,6 +30,11 @@ fn u8_as_i8(x: u8) -> i8 { x as i8 }
 fn odd(x: uint) -> bool { x % 2 == 1 }
 fn dummy_rng() -> DummyRng { DummyRng::new_unseeded() }
 
+trait Size: Sized {
+    fn size() -> uint { std::mem::size_of::<Self>() }
+}
+impl<T> Size for T {}
+
 macro_rules! tests {
     ($($expr:expr, $ty:ty, ($($test:expr),*);)+) => (pub fn main() {$({
         const C: $ty = $expr;
@@ -70,14 +77,31 @@ tests! {
     //    , (vec![b'f', b'o', b'o'], u8_as_i8);
 
     // Trait static methods.
-    // FIXME qualified path expressions aka UFCS i.e. <T as Trait>::method.
+    <bool as Size>::size, fn() -> uint, ();
     Default::default, fn() -> int, ();
+    <int as Default>::default, fn() -> int, ();
     Rand::rand, fn(&mut DummyRng) -> int, (&mut dummy_rng());
+    <int as Rand>::rand, fn(&mut DummyRng) -> int, (&mut dummy_rng());
     Rand::rand::<DummyRng>, fn(&mut DummyRng) -> int, (&mut dummy_rng());
+    <int as Rand>::rand::<DummyRng>, fn(&mut DummyRng) -> int, (&mut dummy_rng());
 
     // Trait non-static methods.
     Clone::clone, fn(&int) -> int, (&5);
+    <int as Clone>::clone, fn(&int) -> int, (&5);
     FromIterator::from_iter, fn(OptionIter<int>) -> Vec<int>, (Some(5).into_iter());
-    FromIterator::from_iter::<OptionIter<int>>, fn(OptionIter<int>) -> Vec<int>
-       , (Some(5).into_iter());
+    <Vec<_> as FromIterator<_>>::from_iter, fn(OptionIter<int>) -> Vec<int>,
+        (Some(5).into_iter());
+    <Vec<int> as FromIterator<_>>::from_iter, fn(OptionIter<int>) -> Vec<int>,
+        (Some(5).into_iter());
+    FromIterator::from_iter::<OptionIter<int>>, fn(OptionIter<int>) -> Vec<int>,
+        (Some(5).into_iter());
+    <Vec<int> as FromIterator<_>>::from_iter::<OptionIter<int>>, fn(OptionIter<int>) -> Vec<int>,
+        (Some(5).into_iter());
+    Add::add, fn(i32, i32) -> i32, (5, 6);
+    <i32 as Add<_>>::add, fn(i32, i32) -> i32, (5, 6);
+    <i32 as Add<i32>>::add, fn(i32, i32) -> i32, (5, 6);
+    <String as IntoCow<_, _>>::into_cow, fn(String) -> Cow<'static, String, str>,
+        ("foo".to_string());
+    <String as IntoCow<'static, _, _>>::into_cow, fn(String) -> Cow<'static, String, str>,
+        ("foo".to_string());
 }