rustc: Perform region inference

Author: pcwalton

src/rustc/driver/driver.rs

@@ -140,7 +140,10 @@ fn compile_upto(sess: session, cfg: ast::crate_cfg,
     let freevars =
         time(time_passes, "freevar finding",
              bind freevars::annotate_freevars(def_map, crate));
-    let ty_cx = ty::mk_ctxt(sess, def_map, ast_map, freevars);
+    let region_map =
+        time(time_passes, "region resolution",
+             bind middle::region::resolve_crate(sess, crate));
+    let ty_cx = ty::mk_ctxt(sess, def_map, ast_map, freevars, region_map);
     let (method_map, dict_map) =
         time(time_passes, "typechecking",
              bind typeck::check_crate(ty_cx, impl_map, crate));

src/rustc/middle/region.rs

@@ -0,0 +1,145 @@
+/*
+ * Region resolution. This pass runs before typechecking and resolves region
+ * names to the appropriate block.
+ */
+
+import driver::session::session;
+import middle::ty;
+import syntax::{ast, visit};
+import std::map;
+import std::map::hashmap;
+
+type region_map = {
+    parent_blocks: hashmap<ast::node_id,ast::node_id>,
+    ast_type_to_region: hashmap<ast::node_id,ty::region>
+};
+
+enum parent {
+    pa_item(ast::node_id),
+    pa_block(ast::node_id),
+    pa_crate
+}
+
+type ctxt = {
+    sess: session,
+    region_map: @region_map,
+    names_in_scope: hashmap<str,ast::def_id>,
+    parent: parent
+};
+
+fn resolve_ty(ty: @ast::ty, cx: ctxt, visitor: visit::vt<ctxt>) {
+    alt ty.node {
+        ast::ty_rptr({id: region_id, node: node}, _) {
+            let region;
+            alt node {
+                ast::re_inferred {
+                    // We infer to the caller region if we're at item scope
+                    // and to the block region if we're at block scope.
+                    alt cx.parent {
+                        pa_item(item_id) {
+                            let def_id = {crate: ast::local_crate,
+                                          node: item_id};
+                            region = ty::re_caller(def_id);
+                        }
+                        pa_block(block_id) {
+                            region = ty::re_block(block_id);
+                        }
+                        pa_crate {
+                            cx.sess.span_bug(ty.span,
+                                             "region type outside item");
+                        }
+                    }
+                }
+
+                ast::re_named(ident) {
+                    // If at item scope, introduce or reuse a binding. If at
+                    // block scope, require that the binding be introduced.
+                    alt cx.names_in_scope.find(ident) {
+                        some(def_id) { region = ty::re_named(def_id); }
+                        none {
+                            alt cx.parent {
+                                pa_item(_) { /* ok; fall through */ }
+                                pa_block(_) {
+                                    cx.sess.span_err(ty.span,
+                                                     "unknown region `" +
+                                                     ident + "`");
+                                }
+                                pa_crate {
+                                    cx.sess.span_bug(ty.span,
+                                                     "named region at " +
+                                                     "crate scope?!");
+                                }
+                            }
+
+                            let def_id = {crate: ast::local_crate,
+                                          node: region_id};
+                            cx.names_in_scope.insert(ident, def_id);
+                            region = ty::re_named(def_id);
+                        }
+                    }
+                }
+
+                ast::re_self {
+                    // For blocks, "self" means "the current block".
+                    alt cx.parent {
+                        pa_item(_) {
+                            cx.sess.span_unimpl(ty.span,
+                                                "'self' region for items");
+                        }
+                        pa_block(block_id) {
+                            region = ty::re_block(block_id);
+                        }
+                        pa_crate {
+                            cx.sess.span_bug(ty.span,
+                                             "region type outside item");
+                        }
+                    }
+                }
+
+            }
+
+            cx.region_map.ast_type_to_region.insert(region_id, region);
+        }
+        _ { /* nothing to do */ }
+    }
+
+    visit::visit_ty(ty, cx, visitor);
+}
+
+fn resolve_block(blk: ast::blk, cx: ctxt, visitor: visit::vt<ctxt>) {
+    alt cx.parent {
+        pa_item(_) { /* no-op */ }
+        pa_block(parent_block_id) {
+            cx.region_map.parent_blocks.insert(blk.node.id, parent_block_id);
+        }
+        pa_crate { cx.sess.span_bug(blk.span, "block outside item?!"); }
+    }
+
+    let new_cx: ctxt = {parent: pa_block(blk.node.id) with cx};
+    visit::visit_block(blk, new_cx, visitor);
+}
+
+fn resolve_item(item: @ast::item, cx: ctxt, visitor: visit::vt<ctxt>) {
+    // Items create a new outer block scope as far as we're concerned.
+    let new_cx: ctxt = {names_in_scope: map::new_str_hash(),
+                        parent: pa_item(item.id)
+                        with cx};
+    visit::visit_item(item, new_cx, visitor);
+}
+
+fn resolve_crate(sess: session, crate: @ast::crate) -> @region_map {
+    let cx: ctxt = {sess: sess,
+                    region_map: @{parent_blocks: map::new_int_hash(),
+                                  ast_type_to_region: map::new_int_hash()},
+                    names_in_scope: map::new_str_hash(),
+                    parent: pa_crate};
+    let visitor = visit::mk_vt(@{
+        visit_block: resolve_block,
+        visit_item: resolve_item,
+        visit_ty: resolve_ty
+        with *visit::default_visitor()
+    });
+    visit::visit_crate(*crate, cx, visitor);
+    ret cx.region_map;
+}
+

src/rustc/middle/ty.rs

@@ -167,6 +167,7 @@ type ctxt =
       mutable next_id: uint,
       sess: session::session,
       def_map: resolve::def_map,
+      region_map: @middle::region::region_map,
       node_types: node_type_table,
       node_type_substs: hashmap<node_id, [t]>,
       items: ast_map::map,
@@ -327,7 +328,8 @@ fn new_ty_hash<V: copy>() -> map::hashmap<t, V> {
 }
 
 fn mk_ctxt(s: session::session, dm: resolve::def_map, amap: ast_map::map,
-           freevars: freevars::freevar_map) -> ctxt {
+           freevars: freevars::freevar_map,
+           region_map: @middle::region::region_map) -> ctxt {
     let interner = map::mk_hashmap({|&&k: intern_key|
         hash_type_structure(k.struct) +
             option::maybe(0u, k.o_def_id, ast_util::hash_def_id)
@@ -336,6 +338,7 @@ fn mk_ctxt(s: session::session, dm: resolve::def_map, amap: ast_map::map,
       mutable next_id: 0u,
       sess: s,
       def_map: dm,
+      region_map: region_map,
       node_types: @smallintmap::mk(),
       node_type_substs: map::new_int_hash(),
       items: amap,

src/rustc/rustc.rc

@@ -44,6 +44,7 @@ mod middle {
     mod freevars;
     mod capture;
     mod pat_util;
+    mod region;
 
     mod tstate {
         mod ck;