Extend allocation lint for boxing expressions

src/librustc/back/link.rs

@@ -428,7 +428,7 @@ fn len_and_str(s: &str) -> ~str {
         }
 
         fn len_and_str_lit(l: ast::lit) -> ~str {
-            len_and_str(pprust::lit_to_str(@l))
+            len_and_str(pprust::lit_to_str(&l))
         }
 
         let cmh_items = attr::sort_meta_items(cmh_items);

src/librustc/front/test.rs

@@ -330,7 +330,7 @@ pub fn main() {
      };
 
     debug!("Synthetic test module:\n{}\n",
-           pprust::item_to_str(@item.clone(), cx.sess.intr()));
+           pprust::item_to_str(&item, cx.sess.intr()));
 
     return @item;
 }

src/librustc/middle/lint.rs

@@ -1028,27 +1028,47 @@ fn check_unused_mut_pat(cx: &Context, p: &ast::Pat) {
     }
 }
 
+enum Allocation {
+    VectorAllocation,
+    BoxAllocation
+}
+
 fn check_unnecessary_allocation(cx: &Context, e: &ast::Expr) {
-    // Warn if string and vector literals with sigils are immediately borrowed.
-    // Those can have the sigil removed.
-    match e.node {
+    // Warn if string and vector literals with sigils, or boxing expressions,
+    // are immediately borrowed.
+    let allocation = match e.node {
         ast::ExprVstore(e2, ast::ExprVstoreUniq) |
         ast::ExprVstore(e2, ast::ExprVstoreBox) => {
             match e2.node {
                 ast::ExprLit(@codemap::Spanned{node: ast::lit_str(..), ..}) |
-                ast::ExprVec(..) => {}
+                ast::ExprVec(..) => VectorAllocation,
                 _ => return
             }
         }
+        ast::ExprUnary(_, ast::UnUniq, _) |
+        ast::ExprUnary(_, ast::UnBox(..), _) => BoxAllocation,
 
         _ => return
-    }
+    };
+
+    let report = |msg| {
+        cx.span_lint(unnecessary_allocation, e.span, msg);
+    };
 
     match cx.tcx.adjustments.find_copy(&e.id) {
-        Some(@ty::AutoDerefRef(ty::AutoDerefRef {
-            autoref: Some(ty::AutoBorrowVec(..)), .. })) => {
-            cx.span_lint(unnecessary_allocation, e.span,
-                         "unnecessary allocation, the sigil can be removed");
+        Some(@ty::AutoDerefRef(ty::AutoDerefRef { autoref, .. })) => {
+            match (allocation, autoref) {
+                (VectorAllocation, Some(ty::AutoBorrowVec(..))) => {
+                    report("unnecessary allocation, the sigil can be removed");
+                }
+                (BoxAllocation, Some(ty::AutoPtr(_, ast::MutImmutable))) => {
+                    report("unnecessary allocation, use & instead");
+                }
+                (BoxAllocation, Some(ty::AutoPtr(_, ast::MutMutable))) => {
+                    report("unnecessary allocation, use &mut instead");
+                }
+                _ => ()
+            }
         }
 
         _ => ()

src/libsyntax/ext/quote.rs

@@ -119,28 +119,28 @@ fn to_source(&self) -> @str {
     impl<'self> ToSource for &'self str {
         fn to_source(&self) -> @str {
             let lit = dummy_spanned(ast::lit_str(self.to_managed(), ast::CookedStr));
-            pprust::lit_to_str(@lit).to_managed()
+            pprust::lit_to_str(&lit).to_managed()
         }
     }
 
     impl ToSource for int {
         fn to_source(&self) -> @str {
             let lit = dummy_spanned(ast::lit_int(*self as i64, ast::ty_i));
-            pprust::lit_to_str(@lit).to_managed()
+            pprust::lit_to_str(&lit).to_managed()
         }
     }
 
     impl ToSource for i8 {
         fn to_source(&self) -> @str {
             let lit = dummy_spanned(ast::lit_int(*self as i64, ast::ty_i8));
-            pprust::lit_to_str(@lit).to_managed()
+            pprust::lit_to_str(&lit).to_managed()
         }
     }
 
     impl ToSource for i16 {
         fn to_source(&self) -> @str {
             let lit = dummy_spanned(ast::lit_int(*self as i64, ast::ty_i16));
-            pprust::lit_to_str(@lit).to_managed()
+            pprust::lit_to_str(&lit).to_managed()
         }
     }
 
@@ -148,49 +148,49 @@ fn to_source(&self) -> @str {
     impl ToSource for i32 {
         fn to_source(&self) -> @str {
             let lit = dummy_spanned(ast::lit_int(*self as i64, ast::ty_i32));
-            pprust::lit_to_str(@lit).to_managed()
+            pprust::lit_to_str(&lit).to_managed()
         }
     }
 
     impl ToSource for i64 {
         fn to_source(&self) -> @str {
             let lit = dummy_spanned(ast::lit_int(*self as i64, ast::ty_i64));
-            pprust::lit_to_str(@lit).to_managed()
+            pprust::lit_to_str(&lit).to_managed()
         }
     }
 
     impl ToSource for uint {
         fn to_source(&self) -> @str {
             let lit = dummy_spanned(ast::lit_uint(*self as u64, ast::ty_u));
-            pprust::lit_to_str(@lit).to_managed()
+            pprust::lit_to_str(&lit).to_managed()
         }
     }
 
     impl ToSource for u8 {
         fn to_source(&self) -> @str {
             let lit = dummy_spanned(ast::lit_uint(*self as u64, ast::ty_u8));
-            pprust::lit_to_str(@lit).to_managed()
+            pprust::lit_to_str(&lit).to_managed()
         }
     }
 
     impl ToSource for u16 {
         fn to_source(&self) -> @str {
             let lit = dummy_spanned(ast::lit_uint(*self as u64, ast::ty_u16));
-            pprust::lit_to_str(@lit).to_managed()
+            pprust::lit_to_str(&lit).to_managed()
         }
     }
 
     impl ToSource for u32 {
         fn to_source(&self) -> @str {
             let lit = dummy_spanned(ast::lit_uint(*self as u64, ast::ty_u32));
-            pprust::lit_to_str(@lit).to_managed()
+            pprust::lit_to_str(&lit).to_managed()
         }
     }
 
     impl ToSource for u64 {
         fn to_source(&self) -> @str {
             let lit = dummy_spanned(ast::lit_uint(*self as u64, ast::ty_u64));
-            pprust::lit_to_str(@lit).to_managed()
+            pprust::lit_to_str(&lit).to_managed()
         }
     }
 

src/libsyntax/print/pprust.rs

@@ -1902,7 +1902,7 @@ pub fn print_meta_item(s: @ps, item: &ast::MetaItem) {
       ast::MetaNameValue(name, value) => {
         word_space(s, name);
         word_space(s, "=");
-        print_literal(s, @value);
+        print_literal(s, &value);
       }
       ast::MetaList(name, ref items) => {
         word(s.s, name);

src/test/compile-fail/lint-allocation.rs

@@ -0,0 +1,19 @@
+// Copyright 2013 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.
+
+#[deny(unnecessary_allocation)];
+
+fn f(_: &int) {}
+fn g(_: &mut int) {}
+
+fn main() {
+    f(~1); //~ ERROR unnecessary allocation, use & instead
+    g(~1); //~ ERROR unnecessary allocation, use &mut instead
+}