auto merge of #14696 : jakub-/rust/dead-struct-fields, r=alexcrichton

This uncovered some dead code, most notably in middle/liveness.rs, which I think suggests there must be something fishy with that part of the code.

The #[allow(dead_code)] annotations on some of the fields I am not super happy about but as I understand, marker type may disappear at some point.

src/libglob/lib.rs

@@ -44,7 +44,6 @@ use std::string::String;
  * pattern - see the `glob` function for more details.
  */
 pub struct Paths {
-    root: Path,
     dir_patterns: Vec<Pattern>,
     require_dir: bool,
     options: MatchOptions,
@@ -108,7 +107,6 @@ pub fn glob_with(pattern: &str, options: MatchOptions) -> Paths {
             // FIXME: How do we want to handle verbatim paths? I'm inclined to return nothing,
             // since we can't very well find all UNC shares with a 1-letter server name.
             return Paths {
-                root: root,
                 dir_patterns: Vec::new(),
                 require_dir: false,
                 options: options,
@@ -134,7 +132,6 @@ pub fn glob_with(pattern: &str, options: MatchOptions) -> Paths {
     }
 
     Paths {
-        root: root,
         dir_patterns: dir_patterns,
         require_dir: require_dir,
         options: options,

src/libgreen/context.rs

@@ -143,6 +143,7 @@ extern {
 // stacks are disabled.
 
 #[cfg(target_arch = "x86")]
+#[repr(C)]
 struct Registers {
     eax: u32, ebx: u32, ecx: u32, edx: u32,
     ebp: u32, esi: u32, edi: u32, esp: u32,

src/libnative/io/c_win32.rs

@@ -20,6 +20,7 @@ pub static FIONBIO: libc::c_long = 0x8004667e;
 static FD_SETSIZE: uint = 64;
 pub static MSG_DONTWAIT: libc::c_int = 0;
 
+#[repr(C)]
 pub struct WSADATA {
     pub wVersion: libc::WORD,
     pub wHighVersion: libc::WORD,
@@ -32,6 +33,7 @@ pub struct WSADATA {
 
 pub type LPWSADATA = *mut WSADATA;
 
+#[repr(C)]
 pub struct fd_set {
     fd_count: libc::c_uint,
     fd_array: [libc::SOCKET, ..FD_SETSIZE],

src/libnative/io/mod.rs

@@ -152,13 +152,13 @@ fn keep_going(data: &[u8], f: |*u8, uint| -> i64) -> i64 {
 /// Implementation of rt::rtio's IoFactory trait to generate handles to the
 /// native I/O functionality.
 pub struct IoFactory {
-    cannot_construct_outside_of_this_module: ()
+    _cannot_construct_outside_of_this_module: ()
 }
 
 impl IoFactory {
     pub fn new() -> IoFactory {
         net::init();
-        IoFactory { cannot_construct_outside_of_this_module: () }
+        IoFactory { _cannot_construct_outside_of_this_module: () }
     }
 }
 

src/libnative/io/net.rs

@@ -254,7 +254,10 @@ pub struct TcpStream {
 
 struct Inner {
     fd: sock_t,
-    lock: mutex::NativeMutex,
+
+    // Unused on Linux, where this lock is not necessary.
+    #[allow(dead_code)]
+    lock: mutex::NativeMutex
 }
 
 pub struct Guard<'a> {

src/libnative/io/pipe_unix.rs

@@ -58,7 +58,10 @@ fn addr_to_sockaddr_un(addr: &CString) -> IoResult<(libc::sockaddr_storage, uint
 
 struct Inner {
     fd: fd_t,
-    lock: mutex::NativeMutex,
+
+    // Unused on Linux, where this lock is not necessary.
+    #[allow(dead_code)]
+    lock: mutex::NativeMutex
 }
 
 impl Inner {

src/librand/distributions/gamma.rs

@@ -81,7 +81,6 @@ struct GammaSmallShape {
 /// See `Gamma` for sampling from a Gamma distribution with general
 /// shape parameters.
 struct GammaLargeShape {
-    shape: f64,
     scale: f64,
     c: f64,
     d: f64
@@ -118,7 +117,6 @@ impl GammaLargeShape {
     fn new_raw(shape: f64, scale: f64) -> GammaLargeShape {
         let d = shape - 1. / 3.;
         GammaLargeShape {
-            shape: shape,
             scale: scale,
             c: 1. / (9. * d).sqrt(),
             d: d

src/librustc/front/std_inject.rs

@@ -130,9 +130,7 @@ fn inject_crates_ref(sess: &Session, krate: ast::Crate) -> ast::Crate {
     fold.fold_crate(krate)
 }
 
-struct PreludeInjector<'a> {
-    sess: &'a Session,
-}
+struct PreludeInjector<'a>;
 
 
 impl<'a> fold::Folder for PreludeInjector<'a> {
@@ -223,9 +221,7 @@ impl<'a> fold::Folder for PreludeInjector<'a> {
     }
 }
 
-fn inject_prelude(sess: &Session, krate: ast::Crate) -> ast::Crate {
-    let mut fold = PreludeInjector {
-        sess: sess,
-    };
+fn inject_prelude(_: &Session, krate: ast::Crate) -> ast::Crate {
+    let mut fold = PreludeInjector;
     fold.fold_crate(krate)
 }

src/librustc/metadata/loader.rs

@@ -86,7 +86,7 @@ pub struct Library {
 }
 
 pub struct ArchiveMetadata {
-    archive: ArchiveRO,
+    _archive: ArchiveRO,
     // See comments in ArchiveMetadata::new for why this is static
     data: &'static [u8],
 }
@@ -487,7 +487,7 @@ impl ArchiveMetadata {
             unsafe { mem::transmute(data) }
         };
         Some(ArchiveMetadata {
-            archive: ar,
+            _archive: ar,
             data: data,
         })
     }

src/librustc/metadata/tyencode.rs

@@ -42,8 +42,6 @@ pub struct ctxt<'a> {
 // Extra parameters are for converting to/from def_ids in the string rep.
 // Whatever format you choose should not contain pipe characters.
 pub struct ty_abbrev {
-    pos: uint,
-    len: uint,
     s: String
 }
 
@@ -68,8 +66,6 @@ pub fn enc_ty(w: &mut MemWriter, cx: &ctxt, t: ty::t) {
     if abbrev_len < len {
         // I.e. it's actually an abbreviation.
         cx.abbrevs.borrow_mut().insert(t, ty_abbrev {
-            pos: pos as uint,
-            len: len as uint,
             s: format!("\\#{:x}:{:x}\\#", pos, len)
         });
     }

src/librustc/middle/borrowck/gather_loans/lifetime.rs

@@ -29,7 +29,7 @@ pub fn guarantee_lifetime(bccx: &BorrowckCtxt,
                           cause: euv::LoanCause,
                           cmt: mc::cmt,
                           loan_region: ty::Region,
-                          loan_kind: ty::BorrowKind)
+                          _: ty::BorrowKind)
                           -> Result<(),()> {
     debug!("guarantee_lifetime(cmt={}, loan_region={})",
            cmt.repr(bccx.tcx), loan_region.repr(bccx.tcx));
@@ -38,7 +38,6 @@ pub fn guarantee_lifetime(bccx: &BorrowckCtxt,
                                          span: span,
                                          cause: cause,
                                          loan_region: loan_region,
-                                         loan_kind: loan_kind,
                                          cmt_original: cmt.clone()};
     ctxt.check(&cmt, None)
 }
@@ -55,7 +54,6 @@ struct GuaranteeLifetimeContext<'a> {
     span: Span,
     cause: euv::LoanCause,
     loan_region: ty::Region,
-    loan_kind: ty::BorrowKind,
     cmt_original: mc::cmt
 }
 

src/librustc/middle/borrowck/gather_loans/mod.rs

@@ -310,7 +310,6 @@ impl<'a> GatherLoanCtxt<'a> {
                 Loan {
                     index: self.all_loans.len(),
                     loan_path: loan_path,
-                    cmt: cmt,
                     kind: req_kind,
                     gen_scope: gen_scope,
                     kill_scope: kill_scope,
@@ -481,8 +480,7 @@ impl<'a> GatherLoanCtxt<'a> {
 /// This visitor walks static initializer's expressions and makes
 /// sure the loans being taken are sound.
 struct StaticInitializerCtxt<'a> {
-    bccx: &'a BorrowckCtxt<'a>,
-    item_ub: ast::NodeId,
+    bccx: &'a BorrowckCtxt<'a>
 }
 
 impl<'a> visit::Visitor<()> for StaticInitializerCtxt<'a> {
@@ -509,8 +507,7 @@ pub fn gather_loans_in_static_initializer(bccx: &mut BorrowckCtxt, expr: &ast::E
     debug!("gather_loans_in_static_initializer(expr={})", expr.repr(bccx.tcx));
 
     let mut sicx = StaticInitializerCtxt {
-        bccx: bccx,
-        item_ub: expr.id,
+        bccx: bccx
     };
 
     sicx.visit_expr(expr, ());

src/librustc/middle/borrowck/gather_loans/restrictions.rs

@@ -36,7 +36,6 @@ pub fn compute_restrictions(bccx: &BorrowckCtxt,
         bccx: bccx,
         span: span,
         cause: cause,
-        cmt_original: cmt.clone(),
         loan_region: loan_region,
     };
 
@@ -49,7 +48,6 @@ pub fn compute_restrictions(bccx: &BorrowckCtxt,
 struct RestrictionsContext<'a> {
     bccx: &'a BorrowckCtxt<'a>,
     span: Span,
-    cmt_original: mc::cmt,
     loan_region: ty::Region,
     cause: euv::LoanCause,
 }

src/librustc/middle/borrowck/mod.rs

@@ -180,7 +180,6 @@ pub enum PartialTotal {
 pub struct Loan {
     index: uint,
     loan_path: Rc<LoanPath>,
-    cmt: mc::cmt,
     kind: ty::BorrowKind,
     restrictions: Vec<Restriction>,
     gen_scope: ast::NodeId,

src/librustc/middle/dead.rs

@@ -124,6 +124,32 @@ impl<'a> MarkSymbolVisitor<'a> {
         }
     }
 
+    fn handle_field_access(&mut self, lhs: &ast::Expr, name: &ast::Ident) {
+        match ty::get(ty::expr_ty_adjusted(self.tcx, lhs)).sty {
+            ty::ty_struct(id, _) => {
+                let fields = ty::lookup_struct_fields(self.tcx, id);
+                let field_id = fields.iter()
+                    .find(|field| field.name == name.name).unwrap().id;
+                self.live_symbols.insert(field_id.node);
+            },
+            _ => ()
+        }
+    }
+
+    fn handle_field_pattern_match(&mut self, lhs: &ast::Pat, pats: &[ast::FieldPat]) {
+        match self.tcx.def_map.borrow().get(&lhs.id) {
+            &def::DefStruct(id) | &def::DefVariant(_, id, _) => {
+                let fields = ty::lookup_struct_fields(self.tcx, id);
+                for pat in pats.iter() {
+                    let field_id = fields.iter()
+                        .find(|field| field.name == pat.ident.name).unwrap().id;
+                    self.live_symbols.insert(field_id.node);
+                }
+            }
+            _ => ()
+        }
+    }
+
     fn mark_live_symbols(&mut self) {
         let mut scanned = HashSet::new();
         while self.worklist.len() > 0 {
@@ -147,10 +173,22 @@ impl<'a> MarkSymbolVisitor<'a> {
         match *node {
             ast_map::NodeItem(item) => {
                 match item.node {
+                    ast::ItemStruct(struct_def, _) => {
+                        let has_extern_repr = item.attrs.iter().fold(attr::ReprAny, |acc, attr| {
+                            attr::find_repr_attr(self.tcx.sess.diagnostic(), attr, acc)
+                        }) == attr::ReprExtern;
+                        let live_fields = struct_def.fields.iter().filter(|f| {
+                            has_extern_repr || match f.node.kind {
+                                ast::NamedField(_, ast::Public) => true,
+                                _ => false
+                            }
+                        });
+                        self.live_symbols.extend(live_fields.map(|f| f.node.id));
+                        visit::walk_item(self, item, ());
+                    }
                     ast::ItemFn(..)
                     | ast::ItemTy(..)
                     | ast::ItemEnum(..)
-                    | ast::ItemStruct(..)
                     | ast::ItemStatic(..) => {
                         visit::walk_item(self, item, ());
                     }
@@ -178,18 +216,32 @@ impl<'a> Visitor<()> for MarkSymbolVisitor<'a> {
             ast::ExprMethodCall(..) => {
                 self.lookup_and_handle_method(expr.id, expr.span);
             }
+            ast::ExprField(ref lhs, ref ident, _) => {
+                self.handle_field_access(*lhs, ident);
+            }
             _ => ()
         }
 
         visit::walk_expr(self, expr, ())
     }
 
+    fn visit_pat(&mut self, pat: &ast::Pat, _: ()) {
+        match pat.node {
+            ast::PatStruct(_, ref fields, _) => {
+                self.handle_field_pattern_match(pat, fields.as_slice());
+            }
+            _ => ()
+        }
+
+        visit::walk_pat(self, pat, ())
+    }
+
     fn visit_path(&mut self, path: &ast::Path, id: ast::NodeId, _: ()) {
         self.lookup_and_handle_definition(&id);
         visit::walk_path(self, path, ());
     }
 
-    fn visit_item(&mut self, _item: &ast::Item, _: ()) {
+    fn visit_item(&mut self, _: &ast::Item, _: ()) {
         // Do not recurse into items. These items will be added to the
         // worklist and recursed into manually if necessary.
     }
@@ -317,6 +369,23 @@ struct DeadVisitor<'a> {
 }
 
 impl<'a> DeadVisitor<'a> {
+    fn should_warn_about_field(&mut self, node: &ast::StructField_) -> bool {
+        let (is_named, has_leading_underscore) = match node.ident() {
+            Some(ref ident) => (true, token::get_ident(*ident).get()[0] == ('_' as u8)),
+            _ => (false, false)
+        };
+        let field_type = ty::node_id_to_type(self.tcx, node.id);
+        let is_marker_field = match ty::ty_to_def_id(field_type) {
+            Some(def_id) => self.tcx.lang_items.items().any(|(_, item)| *item == Some(def_id)),
+            _ => false
+        };
+        is_named
+            && !self.symbol_is_live(node.id, None)
+            && !has_leading_underscore
+            && !is_marker_field
+            && !has_allow_dead_code_or_lang_attr(node.attrs.as_slice())
+    }
+
     // id := node id of an item's definition.
     // ctor_id := `Some` if the item is a struct_ctor (tuple struct),
     //            `None` otherwise.
@@ -399,6 +468,14 @@ impl<'a> Visitor<()> for DeadVisitor<'a> {
         visit::walk_block(self, block, ());
     }
 
+    fn visit_struct_field(&mut self, field: &ast::StructField, _: ()) {
+        if self.should_warn_about_field(&field.node) {
+            self.warn_dead_code(field.node.id, field.span, field.node.ident().unwrap());
+        }
+
+        visit::walk_struct_field(self, field, ());
+    }
+
     // Overwrite so that we don't warn the trait method itself.
     fn visit_trait_method(&mut self, trait_method: &ast::TraitMethod, _: ()) {
         match *trait_method {