Use partial path resolutions in expressions for UFCS desugaring.

Author: eddyb

src/librustc/middle/astconv_util.rs

@@ -17,37 +17,36 @@
 use middle::def;
 use middle::ty::{self, Ty};
 use syntax::ast;
-use syntax::codemap::Span;
 use util::ppaux::Repr;
 
 pub const NO_REGIONS: uint = 1;
 pub const NO_TPS: uint = 2;
 
-pub fn check_path_args(tcx: &ty::ctxt,
-                       span: Span,
-                       segments: &[ast::PathSegment],
-                       flags: uint) {
-    if (flags & NO_TPS) != 0 {
-        if segments.iter().any(|s| s.parameters.has_types()) {
-            span_err!(tcx.sess, span, E0109,
-                "type parameters are not allowed on this type");
+pub fn check_path_args(tcx: &ty::ctxt, segments: &[ast::PathSegment], flags: uint) {
+    for segment in segments {
+        if (flags & NO_TPS) != 0 {
+            for typ in segment.parameters.types() {
+                span_err!(tcx.sess, typ.span, E0109,
+                          "type parameters are not allowed on this type");
+                break;
+            }
         }
-    }
 
-    if (flags & NO_REGIONS) != 0 {
-        if segments.iter().any(|s| s.parameters.has_lifetimes()) {
-            span_err!(tcx.sess, span, E0110,
-                "lifetime parameters are not allowed on this type");
+        if (flags & NO_REGIONS) != 0 {
+            for lifetime in segment.parameters.lifetimes() {
+                span_err!(tcx.sess, lifetime.span, E0110,
+                          "lifetime parameters are not allowed on this type");
+                break;
+            }
         }
     }
 }
 
 pub fn prim_ty_to_ty<'tcx>(tcx: &ty::ctxt<'tcx>,
-                           span: Span,
                            segments: &[ast::PathSegment],
                            nty: ast::PrimTy)
                            -> Ty<'tcx> {
-    check_path_args(tcx, span, segments, NO_TPS | NO_REGIONS);
+    check_path_args(tcx, segments, NO_TPS | NO_REGIONS);
     match nty {
         ast::TyBool => tcx.types.bool,
         ast::TyChar => tcx.types.char,
@@ -69,7 +68,7 @@ pub fn ast_ty_to_prim_ty<'tcx>(tcx: &ty::ctxt<'tcx>, ast_ty: &ast::Ty)
             Some(&d) => d
         };
         if let def::DefPrimTy(nty) = def {
-            Some(prim_ty_to_ty(tcx, path.span, &path.segments[], nty))
+            Some(prim_ty_to_ty(tcx, &path.segments[], nty))
         } else {
             None
         }

src/librustc_resolve/lib.rs

@@ -4055,16 +4055,35 @@ impl<'a, 'tcx> Resolver<'a, 'tcx> {
             // multiple elements in it or not.
 
             ExprPath(ref path) | ExprQPath(ast::QPath { ref path, .. }) => {
-                if let ExprQPath(_) = expr.node {
+                let max_assoc_types = if let ExprQPath(_) = expr.node {
                     // Make sure the trait is valid.
                     let _ = self.resolve_trait_reference(expr.id, path, 1);
+                    1
+                } else {
+                    path.segments.len()
+                };
+
+                let mut result = self.with_no_errors(|this| {
+                    this.resolve_path(expr.id, path, 0, ValueNS, true)
+                });
+                for depth in 1..max_assoc_types {
+                    if result.is_some() {
+                        break;
+                    }
+                    self.with_no_errors(|this| {
+                        result = this.resolve_path(expr.id, path, depth, TypeNS, true);
+                    });
+                }
+                if let Some((DefMod(_), _, _)) = result {
+                    // A module is not a valid type or value.
+                    result = None;
                 }
 
                 // This is a local path in the value namespace. Walk through
                 // scopes looking for it.
-                match self.resolve_path(expr.id, path, 0, ValueNS, true) {
+                match result {
                     // Check if struct variant
-                    Some((DefVariant(_, _, true), _, _)) => {
+                    Some((DefVariant(_, _, true), _, 0)) => {
                         let path_name = self.path_names_to_string(path, 0);
                         self.resolve_error(expr.span,
                                 &format!("`{}` is a struct variant name, but \
@@ -4082,6 +4101,14 @@ impl<'a, 'tcx> Resolver<'a, 'tcx> {
                         debug!("(resolving expr) resolved `{}`",
                                self.path_names_to_string(path, 0));
 
+                        // Partial resolutions will need the set of traits in scope,
+                        // so they can be completed during typeck.
+                        if def.2 != 0 {
+                            let method_name = path.segments.last().unwrap().identifier.name;
+                            let traits = self.search_for_traits_containing_method(method_name);
+                            self.trait_map.insert(expr.id, traits);
+                        }
+
                         self.record_def(expr.id, def);
                     }
                     None => {
@@ -4107,6 +4134,9 @@ impl<'a, 'tcx> Resolver<'a, 'tcx> {
 
                             }
                             _ => {
+                                // Keep reporting some errors even if they're ignored above.
+                                self.resolve_path(expr.id, path, 0, ValueNS, true);
+
                                 let mut method_scope = false;
                                 self.value_ribs.iter().rev().all(|rib| {
                                     method_scope = match rib.kind {