From a1b4afe0670fb1603b056f317a301ed527064ef5 Mon Sep 17 00:00:00 2001
From: Niko Matsakis <niko@alum.mit.edu>
Date: Thu, 21 Mar 2013 16:44:13 -0400
Subject: [PATCH] Update coherence rules to be more flexible for `impl Trait
for Type`
---
src/librustc/middle/typeck/coherence.rs | 91 +++++++++++++------------
1 file changed, 47 insertions(+), 44 deletions(-)
diff --git a/src/librustc/middle/typeck/coherence.rs b/src/librustc/middle/typeck/coherence.rs
index 824ac594e74..0b3eca7c07d 100644
--- a/src/librustc/middle/typeck/coherence.rs
+++ b/src/librustc/middle/typeck/coherence.rs
@@ -104,6 +104,32 @@ pub fn get_base_type(inference_context: @mut InferCtxt,
}
}
+pub fn type_is_defined_in_local_crate(original_type: t) -> bool {
+ /*!
+ *
+ * For coherence, when we have `impl Trait for Type`, we need to
+ * guarantee that `Type` is "local" to the
+ * crate. For our purposes, this means that it must contain
+ * some nominal type defined in this crate.
+ */
+
+ let mut found_nominal = false;
+ do ty::walk_ty(original_type) |t| {
+ match get(t).sty {
+ ty_enum(def_id, _) |
+ ty_trait(def_id, _, _) |
+ ty_struct(def_id, _) => {
+ if def_id.crate == ast::local_crate {
+ found_nominal = true;
+ }
+ }
+
+ _ => { }
+ }
+ }
+ return found_nominal;
+}
+
// Returns the def ID of the base type, if there is one.
pub fn get_base_type_def_id(inference_context: @mut InferCtxt,
span: span,
@@ -161,8 +187,7 @@ pub fn CoherenceChecker(crate_context: @mut CrateCtxt) -> CoherenceChecker {
crate_context: crate_context,
inference_context: new_infer_ctxt(crate_context.tcx),
- base_type_def_ids: HashMap(),
- privileged_implementations: HashMap()
+ base_type_def_ids: HashMap()
}
}
@@ -174,11 +199,6 @@ pub struct CoherenceChecker {
// definition ID.
base_type_def_ids: HashMap<def_id,def_id>,
-
- // A set of implementations in privileged scopes; i.e. those
- // implementations that are defined in the same scope as their base types.
-
- privileged_implementations: HashMap<node_id,()>,
}
pub impl CoherenceChecker {
@@ -615,27 +635,11 @@ pub impl CoherenceChecker {
visit_mod(module_, item.span, item.id, (), visitor);
}
item_impl(_, opt_trait, _, _) => {
- let mut ok = false;
- match self.base_type_def_ids.find(
- &local_def(item.id)) {
-
- None => {
- // Nothing to do.
- }
- Some(base_type_def_id) => {
- // Check to see whether the implementation is
- // in the same crate as its base type.
-
- if base_type_def_id.crate == local_crate {
- // Record that this implementation is OK.
- self.privileged_implementations.insert
- (item.id, ());
- ok = true;
- }
- }
- }
-
- if !ok {
+ // `for_ty` is `Type` in `impl Trait for Type`
+ let for_ty =
+ ty::node_id_to_type(self.crate_context.tcx,
+ item.id);
+ if !type_is_defined_in_local_crate(for_ty) {
// This implementation is not in scope of its base
// type. This still might be OK if the trait is
// defined in the same crate.
@@ -655,25 +659,24 @@ pub impl CoherenceChecker {
implement a trait or \
new type instead");
}
- _ => ()
- }
- for opt_trait.each |trait_ref| {
- // This is OK if and only if the trait was
- // defined in this crate.
+ Some(trait_ref) => {
+ // This is OK if and only if the trait was
+ // defined in this crate.
- let trait_def_id =
- self.trait_ref_to_trait_def_id(
- *trait_ref);
+ let trait_def_id =
+ self.trait_ref_to_trait_def_id(
+ trait_ref);
- if trait_def_id.crate != local_crate {
- let session = self.crate_context.tcx.sess;
- session.span_err(item.span,
- ~"cannot provide an \
- extension \
- implementation for a \
- trait not defined in \
- this crate");
+ if trait_def_id.crate != local_crate {
+ let session = self.crate_context.tcx.sess;
+ session.span_err(item.span,
+ ~"cannot provide an \
+ extension \
+ implementation for a \
+ trait not defined in \
+ this crate");
+ }
}
}
}