auto merge of #12742 : FlaPer87/rust/issue-11411-static-mut-slice, r=nikomatsakis

This PR enables the use of mutable slices in *mutable* static items. The work was started by @xales and I added a follow-up commit that moves the *immutable* restriction to the recently added `check_static`

Closes #11411

Author: bors

src/librustc/middle/borrowck/check_loans.rs

@@ -522,6 +522,9 @@ impl<'a> CheckLoanCtxt<'a> {
                 None => {
                     return true;
                 }
+                Some(mc::AliasableStaticMut) => {
+                    return true;
+                }
                 Some(cause) => {
                     this.bccx.report_aliasability_violation(
                         expr.span,

src/librustc/middle/check_const.rs

@@ -156,6 +156,7 @@ fn check_expr(v: &mut CheckCrateVisitor, e: &Expr, is_const: bool) {
                 }
             }
           }
+          ExprVstore(_, ExprVstoreMutSlice) |
           ExprVstore(_, ExprVstoreSlice) |
           ExprVec(_, MutImmutable) |
           ExprAddrOf(MutImmutable, _) |

src/librustc/middle/check_static.rs

@@ -107,6 +107,10 @@ impl<'a> Visitor<bool> for CheckStaticVisitor<'a> {
             ast::ExprVstore(_, ast::ExprVstoreSlice) => {
                 visit::walk_expr(self, e, is_const);
             }
+            ast::ExprVstore(_, ast::ExprVstoreMutSlice) => {
+                self.tcx.sess.span_err(e.span,
+                                       "static items are not allowed to have mutable slices");
+           },
             ast::ExprUnary(ast::UnBox, _) => {
                 self.tcx.sess.span_err(e.span,
                                    "static items are not allowed to have managed pointers");

src/librustc/middle/trans/consts.rs

@@ -10,7 +10,8 @@
 
 
 use back::abi;
-use lib::llvm::{llvm, ConstFCmp, ConstICmp, SetLinkage, PrivateLinkage, ValueRef, Bool, True};
+use lib::llvm::{llvm, ConstFCmp, ConstICmp, SetLinkage, PrivateLinkage, ValueRef, Bool, True,
+    False};
 use lib::llvm::{IntEQ, IntNE, IntUGT, IntUGE, IntULT, IntULE, IntSGT, IntSGE, IntSLT, IntSLE,
     RealOEQ, RealOGT, RealOGE, RealOLT, RealOLE, RealONE};
 
@@ -574,7 +575,8 @@ fn const_expr_unadjusted(cx: &CrateContext, e: &ast::Expr,
                                                is_local);
             (v, inlineable)
           }
-          ast::ExprVstore(sub, ast::ExprVstoreSlice) => {
+          ast::ExprVstore(sub, store @ ast::ExprVstoreSlice) |
+          ast::ExprVstore(sub, store @ ast::ExprVstoreMutSlice) => {
             match sub.node {
               ast::ExprLit(ref lit) => {
                 match lit.node {
@@ -592,7 +594,8 @@ fn const_expr_unadjusted(cx: &CrateContext, e: &ast::Expr,
                     llvm::LLVMAddGlobal(cx.llmod, llty.to_ref(), name)
                 });
                 llvm::LLVMSetInitializer(gv, cv);
-                llvm::LLVMSetGlobalConstant(gv, True);
+                llvm::LLVMSetGlobalConstant(gv,
+                      if store == ast::ExprVstoreMutSlice { False } else { True });
                 SetLinkage(gv, PrivateLinkage);
                 let p = const_ptrcast(cx, gv, llunitty);
                 (C_struct(cx, [p, C_uint(cx, es.len())], false), false)

src/test/compile-fail/check-static-immutable-mut-slices.rs

@@ -0,0 +1,16 @@
+// Copyright 2014 The Rust Project Developers. See the COPYRIGHT
+// file at the top-level directory of this distribution and at
+// http://rust-lang.org/COPYRIGHT.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+// Checks that immutable static items can't have mutable slices
+
+static TEST: &'static mut [int] = &mut [];
+//~^ ERROR static items are not allowed to have mutable slices
+
+pub fn main() { }

src/test/run-pass/check-static-mut-slices.rs

@@ -0,0 +1,20 @@
+// Copyright 2014 The Rust Project Developers. See the COPYRIGHT
+// file at the top-level directory of this distribution and at
+// http://rust-lang.org/COPYRIGHT.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+// Checks that mutable static items can have mutable slices
+
+static mut TEST: &'static mut [int] = &mut [1];
+
+pub fn main() {
+    unsafe {
+        TEST[0] += 1;
+        assert_eq!(TEST[0], 2);
+    }
+}