auto merge of #5307 : nikomatsakis/rust/remove-by-val, r=nikomatsakis

This is done in two steps:

First, we make foreign functions not consider modes at all.  This is because previously ++ mode was the only way to pass structs to foreign functions and so forth.  We also add a lint mode warning if you use `&&` mode in a foreign function, since the semantics of that change (it used to pass a pointer to the C function, now it doesn't).

Then, we remove by value and make it equivalent to `+` mode.  At the same time, we stop parsing `-` mode and convert all uses of it to `+` mode (it was already being parsed to `+` mode anyhow).

This obsoletes pull request #5298.

r? @brson

6 files changed, 19 insertions, 11 deletions

diff --git a/src/libsyntax/ast.rs b/src/libsyntax/ast.rs
index b22018c4c76..298cb241bed 100644
--- a/src/libsyntax/ast.rs
+++ b/src/libsyntax/ast.rs
@@ -456,7 +456,7 @@ impl<T:to_bytes::IterBytes> to_bytes::IterBytes for inferable<T> {
 #[auto_encode]
 #[auto_decode]
 #[deriving_eq]
-pub enum rmode { by_ref, by_val, by_copy }
+pub enum rmode { by_ref, by_copy }
 
 impl to_bytes::IterBytes for rmode {
     pure fn iter_bytes(&self, +lsb0: bool, f: to_bytes::Cb) {
diff --git a/src/libsyntax/ast_map.rs b/src/libsyntax/ast_map.rs
index a7d5c0ce75f..a97007cfb3a 100644
--- a/src/libsyntax/ast_map.rs
+++ b/src/libsyntax/ast_map.rs
@@ -148,7 +148,7 @@ pub fn map_crate(diag: span_handler, c: crate) -> map {
 // the item itself.
 pub fn map_decoded_item(diag: span_handler,
                         map: map,
-                        path: path,
+                        +path: path,
                         ii: inlined_item) {
     // I believe it is ok for the local IDs of inlined items from other crates
     // to overlap with the local ids from this crate, so just generate the ids
@@ -171,10 +171,10 @@ pub fn map_decoded_item(diag: span_handler,
       ii_item(*) | ii_dtor(*) => { /* fallthrough */ }
       ii_foreign(i) => {
         cx.map.insert(i.id, node_foreign_item(i, foreign_abi_rust_intrinsic,
-                                              @/*bad*/ copy path));
+                                              @path));
       }
       ii_method(impl_did, m) => {
-        map_method(impl_did, @/*bad*/ copy path, m, cx);
+        map_method(impl_did, @path, m, cx);
       }
     }
 
diff --git a/src/libsyntax/attr.rs b/src/libsyntax/attr.rs
index fb7143f7c14..cd7f9a7cf82 100644
--- a/src/libsyntax/attr.rs
+++ b/src/libsyntax/attr.rs
@@ -72,7 +72,7 @@ pub fn attr_meta(attr: ast::attribute) -> @ast::meta_item {
 }
 
 // Get the meta_items from inside a vector of attributes
-pub fn attr_metas(attrs: ~[ast::attribute]) -> ~[@ast::meta_item] {
+pub fn attr_metas(attrs: &[ast::attribute]) -> ~[@ast::meta_item] {
     do attrs.map |a| { attr_meta(*a) }
 }
 
@@ -214,7 +214,7 @@ pub fn attrs_contains_name(attrs: &[ast::attribute], name: &str) -> bool {
     !find_attrs_by_name(attrs, name).is_empty()
 }
 
-pub fn first_attr_value_str_by_name(attrs: ~[ast::attribute], name: &str)
+pub fn first_attr_value_str_by_name(attrs: &[ast::attribute], name: &str)
                                  -> Option<@~str> {
 
     let mattrs = find_attrs_by_name(attrs, name);
@@ -304,7 +304,7 @@ pub fn find_linkage_metas(attrs: &[ast::attribute]) -> ~[@ast::meta_item] {
     }
 }
 
-pub fn foreign_abi(attrs: ~[ast::attribute])
+pub fn foreign_abi(attrs: &[ast::attribute])
                 -> Either<~str, ast::foreign_abi> {
     return match attr::first_attr_value_str_by_name(attrs, ~"abi") {
         None => {
diff --git a/src/libsyntax/parse/obsolete.rs b/src/libsyntax/parse/obsolete.rs
index ef858a2d5eb..2ade0810dea 100644
--- a/src/libsyntax/parse/obsolete.rs
+++ b/src/libsyntax/parse/obsolete.rs
@@ -55,6 +55,7 @@ pub enum ObsoleteSyntax {
     ObsoletePostFnTySigil,
     ObsoleteBareFnType,
     ObsoleteNewtypeEnum,
+    ObsoleteMode,
 }
 
 impl to_bytes::IterBytes for ObsoleteSyntax {
@@ -176,6 +177,10 @@ pub impl Parser {
                 "newtype enum",
                 "instead of `enum Foo = int`, write `struct Foo(int)`"
             ),
+            ObsoleteMode => (
+                "obsolete argument mode",
+                "replace `-` or `++` mode with `+`"
+            ),
         };
 
         self.report(sp, kind, kind_str, desc);
diff --git a/src/libsyntax/parse/parser.rs b/src/libsyntax/parse/parser.rs
index 0c38b2f5ab5..77ba27cf423 100644
--- a/src/libsyntax/parse/parser.rs
+++ b/src/libsyntax/parse/parser.rs
@@ -17,7 +17,7 @@ use ast::{RegionTyParamBound, TraitTyParamBound};
 use ast::{provided, public, pure_fn, purity};
 use ast::{_mod, add, arg, arm, attribute, bind_by_ref, bind_infer};
 use ast::{bind_by_copy, bitand, bitor, bitxor, blk};
-use ast::{blk_check_mode, box, by_copy, by_ref, by_val};
+use ast::{blk_check_mode, box, by_copy, by_ref};
 use ast::{crate, crate_cfg, decl, decl_item};
 use ast::{decl_local, default_blk, deref, div, enum_def, enum_variant_kind};
 use ast::{expl, expr, expr_, expr_addr_of, expr_match, expr_again};
@@ -78,6 +78,7 @@ use parse::obsolete::{ObsoleteMutVector, ObsoleteTraitImplVisibility};
 use parse::obsolete::{ObsoleteRecordType, ObsoleteRecordPattern};
 use parse::obsolete::{ObsoleteAssertion, ObsoletePostFnTySigil};
 use parse::obsolete::{ObsoleteBareFnType, ObsoleteNewtypeEnum};
+use parse::obsolete::{ObsoleteMode};
 use parse::prec::{as_prec, token_to_binop};
 use parse::token::{can_begin_expr, is_ident, is_ident_or_path};
 use parse::token::{is_plain_ident, INTERPOLATED, special_idents};
@@ -716,12 +717,15 @@ pub impl Parser {
 
     fn parse_arg_mode(&self) -> mode {
         if self.eat(&token::BINOP(token::MINUS)) {
-            expl(by_copy) // NDM outdated syntax
+            self.obsolete(*self.span, ObsoleteMode);
+            expl(by_copy)
         } else if self.eat(&token::ANDAND) {
             expl(by_ref)
         } else if self.eat(&token::BINOP(token::PLUS)) {
             if self.eat(&token::BINOP(token::PLUS)) {
-                expl(by_val)
+                // ++ mode is obsolete, but we need a snapshot
+                // to stop parsing it.
+                expl(by_copy)
             } else {
                 expl(by_copy)
             }
diff --git a/src/libsyntax/print/pprust.rs b/src/libsyntax/print/pprust.rs
index 92883123782..84656063646 100644
--- a/src/libsyntax/print/pprust.rs
+++ b/src/libsyntax/print/pprust.rs
@@ -1710,7 +1710,6 @@ pub fn mode_to_str(m: ast::mode) -> ~str {
     match m {
       ast::expl(ast::by_ref) => ~"&&",
       ast::expl(ast::by_copy) => ~"+",
-      ast::expl(ast::by_val) => ~"++",
       ast::infer(_) => ~""
     }
 }