auto merge of #15929 : pcwalton/rust/by-ref-closures, r=alexcrichton

by-reference upvars.

This partially implements RFC 38. A snapshot will be needed to turn this
on, because stage0 cannot yet parse the keyword.

Part of #12831.

r? @alexcrichton

src/librustc/driver/driver.rs

@@ -360,8 +360,9 @@ pub fn phase_3_run_analysis_passes(sess: Session,
             plugin::build::find_plugin_registrar(
                 sess.diagnostic(), krate)));
 
-    let freevars = time(time_passes, "freevar finding", (), |_|
-                        freevars::annotate_freevars(&def_map, krate));
+    let (freevars, capture_modes) =
+        time(time_passes, "freevar finding", (), |_|
+             freevars::annotate_freevars(&def_map, krate));
 
     let region_map = time(time_passes, "region resolution", (), |_|
                           middle::region::resolve_crate(&sess, krate));
@@ -372,8 +373,15 @@ pub fn phase_3_run_analysis_passes(sess: Session,
     let stability_index = time(time_passes, "stability index", (), |_|
                                stability::Index::build(krate));
 
-    let ty_cx = ty::mk_ctxt(sess, def_map, named_region_map, ast_map,
-                            freevars, region_map, lang_items, stability_index);
+    let ty_cx = ty::mk_ctxt(sess,
+                            def_map,
+                            named_region_map,
+                            ast_map,
+                            freevars,
+                            capture_modes,
+                            region_map,
+                            lang_items,
+                            stability_index);
 
     // passes are timed inside typeck
     typeck::check_crate(&ty_cx, trait_map, krate);

src/librustc/metadata/common.rs

@@ -141,9 +141,10 @@ pub enum astencode_tag { // Reserves 0x40 -- 0x5f
     tag_table_capture_map = 0x53,
     tag_table_unboxed_closure_type = 0x54,
     tag_table_upvar_borrow_map = 0x55,
+    tag_table_capture_modes = 0x56,
 }
 static first_astencode_tag: uint = tag_ast as uint;
-static last_astencode_tag: uint = tag_table_upvar_borrow_map as uint;
+static last_astencode_tag: uint = tag_table_capture_modes as uint;
 impl astencode_tag {
     pub fn from_uint(value : uint) -> Option<astencode_tag> {
         let is_a_tag = first_astencode_tag <= value && value <= last_astencode_tag;

src/librustc/middle/astencode.rs

@@ -18,8 +18,8 @@ use driver::session::Session;
 use metadata::decoder;
 use middle::def;
 use e = metadata::encoder;
+use middle::freevars::{CaptureMode, freevar_entry};
 use middle::freevars;
-use middle::freevars::freevar_entry;
 use middle::region;
 use metadata::tydecode;
 use metadata::tydecode::{DefIdSource, NominalType, TypeWithId, TypeParameter,
@@ -530,9 +530,14 @@ fn encode_freevar_entry(rbml_w: &mut Encoder, fv: &freevar_entry) {
     (*fv).encode(rbml_w).unwrap();
 }
 
+fn encode_capture_mode(rbml_w: &mut Encoder, cm: CaptureMode) {
+    cm.encode(rbml_w).unwrap();
+}
+
 trait rbml_decoder_helper {
     fn read_freevar_entry(&mut self, xcx: &ExtendedDecodeContext)
                           -> freevar_entry;
+    fn read_capture_mode(&mut self) -> CaptureMode;
 }
 
 impl<'a> rbml_decoder_helper for reader::Decoder<'a> {
@@ -541,6 +546,11 @@ impl<'a> rbml_decoder_helper for reader::Decoder<'a> {
         let fv: freevar_entry = Decodable::decode(self).unwrap();
         fv.tr(xcx)
     }
+
+    fn read_capture_mode(&mut self) -> CaptureMode {
+        let cm: CaptureMode = Decodable::decode(self).unwrap();
+        cm
+    }
 }
 
 impl tr for freevar_entry {
@@ -1096,6 +1106,15 @@ fn encode_side_tables_for_id(ecx: &e::EncodeContext,
         }
     }
 
+    for &cm in tcx.capture_modes.borrow().find(&id).iter() {
+        rbml_w.tag(c::tag_table_capture_modes, |rbml_w| {
+            rbml_w.id(id);
+            rbml_w.tag(c::tag_table_val, |rbml_w| {
+                encode_capture_mode(rbml_w, *cm);
+            })
+        })
+    }
+
     let lid = ast::DefId { krate: ast::LOCAL_CRATE, node: id };
     for &pty in tcx.tcache.borrow().find(&lid).iter() {
         rbml_w.tag(c::tag_table_tcache, |rbml_w| {
@@ -1509,6 +1528,13 @@ fn decode_side_tables(xcx: &ExtendedDecodeContext,
                         let ub: ty::UpvarBorrow = Decodable::decode(val_dsr).unwrap();
                         dcx.tcx.upvar_borrow_map.borrow_mut().insert(upvar_id, ub.tr(xcx));
                     }
+                    c::tag_table_capture_modes => {
+                        let capture_mode = val_dsr.read_capture_mode();
+                        dcx.tcx
+                           .capture_modes
+                           .borrow_mut()
+                           .insert(id, capture_mode);
+                    }
                     c::tag_table_tcache => {
                         let pty = val_dsr.read_polytype(xcx);
                         let lid = ast::DefId { krate: ast::LOCAL_CRATE, node: id };

src/librustc/middle/borrowck/mod.rs

@@ -291,7 +291,7 @@ pub fn closure_to_block(closure_id: ast::NodeId,
     match tcx.map.get(closure_id) {
         ast_map::NodeExpr(expr) => match expr.node {
             ast::ExprProc(_decl, block) |
-            ast::ExprFnBlock(_decl, block) => { block.id }
+            ast::ExprFnBlock(_, _decl, block) => { block.id }
             _ => fail!("encountered non-closure id: {}", closure_id)
         },
         _ => fail!("encountered non-expr id: {}", closure_id)

src/librustc/middle/check_loop.rs

@@ -46,9 +46,9 @@ impl<'a> Visitor<Context> for CheckLoopVisitor<'a> {
                 self.visit_expr(&**e, cx);
                 self.visit_block(&**b, Loop);
             }
-            ast::ExprFnBlock(_, ref b) |
+            ast::ExprFnBlock(_, _, ref b) |
             ast::ExprProc(_, ref b) |
-            ast::ExprUnboxedFn(_, ref b) => {
+            ast::ExprUnboxedFn(_, _, ref b) => {
                 self.visit_block(&**b, Closure);
             }
             ast::ExprBreak(_) => self.require_loop("break", cx, e.span),

src/librustc/middle/freevars.rs

@@ -17,14 +17,14 @@ use middle::def;
 use middle::mem_categorization::Typer;
 use middle::resolve;
 use middle::ty;
-use util::nodemap::{DefIdSet, NodeMap, NodeSet};
+use util::nodemap::{NodeMap, NodeSet};
 
+use syntax::ast;
 use syntax::codemap::Span;
-use syntax::{ast};
-use syntax::visit;
 use syntax::visit::Visitor;
+use syntax::visit;
 
-#[deriving(Show)]
+#[deriving(Clone, Decodable, Encodable, Show)]
 pub enum CaptureMode {
     /// Copy/move the value from this llvm ValueRef into the environment.
     CaptureByValue,
@@ -43,12 +43,13 @@ pub struct freevar_entry {
 
 pub type freevar_map = NodeMap<Vec<freevar_entry>>;
 
-pub type UnboxedClosureList = DefIdSet;
+pub type CaptureModeMap = NodeMap<CaptureMode>;
 
 struct CollectFreevarsVisitor<'a> {
     seen: NodeSet,
     refs: Vec<freevar_entry>,
     def_map: &'a resolve::DefMap,
+    capture_mode_map: &'a mut CaptureModeMap,
 }
 
 impl<'a> Visitor<int> for CollectFreevarsVisitor<'a> {
@@ -58,8 +59,27 @@ impl<'a> Visitor<int> for CollectFreevarsVisitor<'a> {
 
     fn visit_expr(&mut self, expr: &ast::Expr, depth: int) {
         match expr.node {
-            ast::ExprFnBlock(..) | ast::ExprProc(..) |
-            ast::ExprUnboxedFn(..) => {
+            ast::ExprProc(..) => {
+                self.capture_mode_map.insert(expr.id, CaptureByValue);
+                visit::walk_expr(self, expr, depth + 1)
+            }
+            ast::ExprFnBlock(_, _, _) => {
+                // NOTE(stage0): After snapshot, change to:
+                //
+                //let capture_mode = match capture_clause {
+                //    ast::CaptureByValue => CaptureByValue,
+                //    ast::CaptureByRef => CaptureByRef,
+                //};
+                let capture_mode = CaptureByRef;
+                self.capture_mode_map.insert(expr.id, capture_mode);
+                visit::walk_expr(self, expr, depth + 1)
+            }
+            ast::ExprUnboxedFn(capture_clause, _, _) => {
+                let capture_mode = match capture_clause {
+                    ast::CaptureByValue => CaptureByValue,
+                    ast::CaptureByRef => CaptureByRef,
+                };
+                self.capture_mode_map.insert(expr.id, capture_mode);
                 visit::walk_expr(self, expr, depth + 1)
             }
             ast::ExprPath(..) => {
@@ -91,35 +111,41 @@ impl<'a> Visitor<int> for CollectFreevarsVisitor<'a> {
             _ => visit::walk_expr(self, expr, depth)
         }
     }
-
-
 }
 
 // Searches through part of the AST for all references to locals or
 // upvars in this frame and returns the list of definition IDs thus found.
 // Since we want to be able to collect upvars in some arbitrary piece
 // of the AST, we take a walker function that we invoke with a visitor
 // in order to start the search.
-fn collect_freevars(def_map: &resolve::DefMap, blk: &ast::Block) -> Vec<freevar_entry> {
+fn collect_freevars(def_map: &resolve::DefMap,
+                    blk: &ast::Block,
+                    capture_mode_map: &mut CaptureModeMap)
+                    -> Vec<freevar_entry> {
     let mut v = CollectFreevarsVisitor {
         seen: NodeSet::new(),
         refs: Vec::new(),
         def_map: def_map,
+        capture_mode_map: &mut *capture_mode_map,
     };
 
     v.visit_block(blk, 1);
+
     v.refs
 }
 
 struct AnnotateFreevarsVisitor<'a> {
     def_map: &'a resolve::DefMap,
     freevars: freevar_map,
+    capture_mode_map: CaptureModeMap,
 }
 
 impl<'a> Visitor<()> for AnnotateFreevarsVisitor<'a> {
     fn visit_fn(&mut self, fk: &visit::FnKind, fd: &ast::FnDecl,
                 blk: &ast::Block, s: Span, nid: ast::NodeId, _: ()) {
-        let vars = collect_freevars(self.def_map, blk);
+        let vars = collect_freevars(self.def_map,
+                                    blk,
+                                    &mut self.capture_mode_map);
         self.freevars.insert(nid, vars);
         visit::walk_fn(self, fk, fd, blk, s, ());
     }
@@ -131,14 +157,20 @@ impl<'a> Visitor<()> for AnnotateFreevarsVisitor<'a> {
 // node of interest rather than building up the free variables in
 // one pass. This could be improved upon if it turns out to matter.
 pub fn annotate_freevars(def_map: &resolve::DefMap, krate: &ast::Crate)
-                         -> freevar_map {
+                         -> (freevar_map, CaptureModeMap) {
     let mut visitor = AnnotateFreevarsVisitor {
         def_map: def_map,
         freevars: NodeMap::new(),
+        capture_mode_map: NodeMap::new(),
     };
     visit::walk_crate(&mut visitor, krate, ());
 
-    visitor.freevars
+    let AnnotateFreevarsVisitor {
+        freevars,
+        capture_mode_map,
+        ..
+    } = visitor;
+    (freevars, capture_mode_map)
 }
 
 pub fn with_freevars<T>(tcx: &ty::ctxt, fid: ast::NodeId, f: |&[freevar_entry]| -> T) -> T {
@@ -148,10 +180,7 @@ pub fn with_freevars<T>(tcx: &ty::ctxt, fid: ast::NodeId, f: |&[freevar_entry]|
     }
 }
 
-pub fn get_capture_mode<T: Typer>(tcx: &T, closure_expr_id: ast::NodeId) -> CaptureMode {
-    let fn_ty = tcx.node_ty(closure_expr_id).ok().expect("couldn't find closure ty?");
-    match ty::ty_closure_store(fn_ty) {
-        ty::RegionTraitStore(..) => CaptureByRef,
-        ty::UniqTraitStore => CaptureByValue
-    }
+pub fn get_capture_mode<T:Typer>(tcx: &T, closure_expr_id: ast::NodeId)
+                        -> CaptureMode {
+    tcx.capture_mode(closure_expr_id)
 }

src/librustc/middle/liveness.rs

@@ -965,9 +965,9 @@ impl<'a> Liveness<'a> {
               self.propagate_through_expr(&**e, succ)
           }
 
-          ExprFnBlock(_, ref blk) |
+          ExprFnBlock(_, _, ref blk) |
           ExprProc(_, ref blk) |
-          ExprUnboxedFn(_, ref blk) => {
+          ExprUnboxedFn(_, _, ref blk) => {
               debug!("{} is an ExprFnBlock, ExprProc, or ExprUnboxedFn",
                      expr_to_string(expr));
 

src/librustc/middle/mem_categorization.rs

@@ -63,6 +63,7 @@
 #![allow(non_camel_case_types)]
 
 use middle::def;
+use middle::freevars;
 use middle::ty;
 use middle::typeck;
 use util::nodemap::NodeMap;
@@ -270,6 +271,8 @@ pub trait Typer {
     fn is_method_call(&self, id: ast::NodeId) -> bool;
     fn temporary_scope(&self, rvalue_id: ast::NodeId) -> Option<ast::NodeId>;
     fn upvar_borrow(&self, upvar_id: ty::UpvarId) -> ty::UpvarBorrow;
+    fn capture_mode(&self, closure_expr_id: ast::NodeId)
+                    -> freevars::CaptureMode;
 }
 
 impl MutabilityCategory {

src/librustc/middle/resolve.rs

@@ -5287,9 +5287,9 @@ impl<'a> Resolver<'a> {
                 visit::walk_expr(self, expr, ());
             }
 
-            ExprFnBlock(fn_decl, block) |
+            ExprFnBlock(_, fn_decl, block) |
             ExprProc(fn_decl, block) |
-            ExprUnboxedFn(fn_decl, block) => {
+            ExprUnboxedFn(_, fn_decl, block) => {
                 self.resolve_function(FunctionRibKind(expr.id, block.id),
                                       Some(fn_decl), NoTypeParameters,
                                       block);

src/librustc/middle/save/mod.rs

@@ -1237,7 +1237,7 @@ impl<'l> Visitor<DxrVisitorEnv> for DxrVisitor<'l> {
                                             "Expected struct type, but not ty_struct"),
                 }
             },
-            ast::ExprFnBlock(decl, body) => {
+            ast::ExprFnBlock(_, decl, body) => {
                 if generated_code(body.span) {
                     return
                 }

src/librustc/middle/trans/base.rs

@@ -1306,7 +1306,9 @@ fn has_nested_returns(tcx: &ty::ctxt, id: ast::NodeId) -> bool {
         }
         Some(ast_map::NodeExpr(e)) => {
             match e.node {
-                ast::ExprFnBlock(_, blk) | ast::ExprProc(_, blk) | ast::ExprUnboxedFn(_, blk) => {
+                ast::ExprFnBlock(_, _, blk) |
+                ast::ExprProc(_, blk) |
+                ast::ExprUnboxedFn(_, _, blk) => {
                     let mut explicit = CheckForNestedReturnsVisitor { found: false };
                     let mut implicit = CheckForNestedReturnsVisitor { found: false };
                     visit::walk_expr(&mut explicit, &*e, false);

src/librustc/middle/trans/common.rs

@@ -18,6 +18,7 @@ use llvm::{ValueRef, BasicBlockRef, BuilderRef};
 use llvm::{True, False, Bool};
 use mc = middle::mem_categorization;
 use middle::def;
+use middle::freevars;
 use middle::lang_items::LangItem;
 use middle::subst;
 use middle::subst::Subst;
@@ -516,6 +517,11 @@ impl<'a> mc::Typer for Block<'a> {
     fn upvar_borrow(&self, upvar_id: ty::UpvarId) -> ty::UpvarBorrow {
         self.tcx().upvar_borrow_map.borrow().get_copy(&upvar_id)
     }
+
+    fn capture_mode(&self, closure_expr_id: ast::NodeId)
+                    -> freevars::CaptureMode {
+        self.tcx().capture_modes.borrow().get_copy(&closure_expr_id)
+    }
 }
 
 pub struct Result<'a> {

src/librustc/middle/trans/debuginfo.rs

@@ -1150,9 +1150,9 @@ pub fn create_function_debug_context(cx: &CrateContext,
         }
         ast_map::NodeExpr(ref expr) => {
             match expr.node {
-                ast::ExprFnBlock(fn_decl, top_level_block) |
+                ast::ExprFnBlock(_, fn_decl, top_level_block) |
                 ast::ExprProc(fn_decl, top_level_block) |
-                ast::ExprUnboxedFn(fn_decl, top_level_block) => {
+                ast::ExprUnboxedFn(_, fn_decl, top_level_block) => {
                     let name = format!("fn{}", token::gensym("fn"));
                     let name = token::str_to_ident(name.as_slice());
                     (name, fn_decl,
@@ -3618,9 +3618,9 @@ fn populate_scope_map(cx: &CrateContext,
                 })
             }
 
-            ast::ExprFnBlock(ref decl, ref block) |
+            ast::ExprFnBlock(_, ref decl, ref block) |
             ast::ExprProc(ref decl, ref block) |
-            ast::ExprUnboxedFn(ref decl, ref block) => {
+            ast::ExprUnboxedFn(_, ref decl, ref block) => {
                 with_new_scope(cx,
                                block.span,
                                scope_stack,

src/librustc/middle/trans/expr.rs

@@ -782,15 +782,15 @@ fn trans_rvalue_dps_unadjusted<'a>(bcx: &'a Block<'a>,
         ast::ExprVec(..) | ast::ExprRepeat(..) => {
             tvec::trans_fixed_vstore(bcx, expr, expr, dest)
         }
-        ast::ExprFnBlock(ref decl, ref body) |
+        ast::ExprFnBlock(_, ref decl, ref body) |
         ast::ExprProc(ref decl, ref body) => {
             let expr_ty = expr_ty(bcx, expr);
             let store = ty::ty_closure_store(expr_ty);
             debug!("translating block function {} with type {}",
                    expr_to_string(expr), expr_ty.repr(tcx));
             closure::trans_expr_fn(bcx, store, &**decl, &**body, expr.id, dest)
         }
-        ast::ExprUnboxedFn(decl, body) => {
+        ast::ExprUnboxedFn(_, decl, body) => {
             closure::trans_unboxed_closure(bcx, &*decl, &*body, expr.id, dest)
         }
         ast::ExprCall(ref f, ref args) => {