Auto merge of #22838 - petrochenkov:bytelit, r=alexcrichton

This patch changes the type of byte string literals from `&[u8]` to `&[u8; N]`.
It also implements some necessary traits (`IntoBytes`, `Seek`, `Read`, `BufRead`) for fixed-size arrays (also related to #21725) and adds test for #17233, which seems to be resolved.

Fixes #18465
[breaking-change]

Author: bors

src/libcore/array.rs

@@ -23,10 +23,34 @@ use marker::{Copy, Sized};
 use option::Option;
 use slice::{Iter, IterMut, SliceExt};
 
+/// Utility trait implemented only on arrays of fixed size
+///
+/// This trait can be used to implement other traits on fixed-size arrays
+/// without causing much metadata bloat.
+#[unstable(feature = "core")]
+pub trait FixedSizeArray<T> {
+    /// Converts the array to immutable slice
+    fn as_slice(&self) -> &[T];
+    /// Converts the array to mutable slice
+    fn as_mut_slice(&mut self) -> &mut [T];
+}
+
 // macro for implementing n-ary tuple functions and operations
 macro_rules! array_impls {
     ($($N:expr)+) => {
         $(
+            #[unstable(feature = "core")]
+            impl<T> FixedSizeArray<T> for [T; $N] {
+                #[inline]
+                fn as_slice(&self) -> &[T] {
+                    &self[..]
+                }
+                #[inline]
+                fn as_mut_slice(&mut self) -> &mut [T] {
+                    &mut self[..]
+                }
+            }
+
             #[stable(feature = "rust1", since = "1.0.0")]
             impl<T:Copy> Clone for [T; $N] {
                 fn clone(&self) -> [T; $N] {

src/libcore/lib.rs

@@ -129,6 +129,7 @@ pub mod default;
 /* Core types and methods on primitives */
 
 pub mod any;
+pub mod array;
 pub mod atomic;
 pub mod cell;
 pub mod char;
@@ -151,7 +152,6 @@ mod bool {
 
 // note: does not need to be public
 mod tuple;
-mod array;
 
 #[doc(hidden)]
 mod core {

src/libcore/result.rs

@@ -448,7 +448,8 @@ impl<T, E> Result<T, E> {
     /// ```
     /// use std::old_io::IoResult;
     ///
-    /// let mut buffer = &mut b"1\n2\n3\n4\n";
+    /// let mut buffer: &[u8] = b"1\n2\n3\n4\n";
+    /// let mut buffer = &mut buffer;
     ///
     /// let mut sum = 0;
     ///

src/librustc_trans/trans/_match.rs

@@ -200,7 +200,7 @@ use middle::mem_categorization as mc;
 use middle::pat_util::*;
 use trans::adt;
 use trans::base::*;
-use trans::build::{AddCase, And, BitCast, Br, CondBr, GEPi, InBoundsGEP, Load};
+use trans::build::{AddCase, And, Br, CondBr, GEPi, InBoundsGEP, Load, PointerCast};
 use trans::build::{Not, Store, Sub, add_comment};
 use trans::build;
 use trans::callee;
@@ -853,14 +853,31 @@ fn compare_values<'blk, 'tcx>(cx: Block<'blk, 'tcx>,
             ty::ty_str => compare_str(cx, lhs, rhs, rhs_t, debug_loc),
             ty::ty_vec(ty, _) => match ty.sty {
                 ty::ty_uint(ast::TyU8) => {
-                    // NOTE: cast &[u8] to &str and abuse the str_eq lang item,
+                    // NOTE: cast &[u8] and &[u8; N] to &str and abuse the str_eq lang item,
                     // which calls memcmp().
-                    let t = ty::mk_str_slice(cx.tcx(),
-                                             cx.tcx().mk_region(ty::ReStatic),
-                                             ast::MutImmutable);
-                    let lhs = BitCast(cx, lhs, type_of::type_of(cx.ccx(), t).ptr_to());
-                    let rhs = BitCast(cx, rhs, type_of::type_of(cx.ccx(), t).ptr_to());
-                    compare_str(cx, lhs, rhs, rhs_t, debug_loc)
+                    let pat_len = val_ty(rhs).element_type().array_length();
+                    let ty_str_slice = ty::mk_str_slice(cx.tcx(),
+                                                        cx.tcx().mk_region(ty::ReStatic),
+                                                        ast::MutImmutable);
+
+                    let rhs_str = alloc_ty(cx, ty_str_slice, "rhs_str");
+                    Store(cx, GEPi(cx, rhs, &[0, 0]), expr::get_dataptr(cx, rhs_str));
+                    Store(cx, C_uint(cx.ccx(), pat_len), expr::get_len(cx, rhs_str));
+
+                    let lhs_str;
+                    if val_ty(lhs) == val_ty(rhs) {
+                        // Both the discriminant and the pattern are thin pointers
+                        lhs_str = alloc_ty(cx, ty_str_slice, "lhs_str");
+                        Store(cx, GEPi(cx, lhs, &[0, 0]), expr::get_dataptr(cx, lhs_str));
+                        Store(cx, C_uint(cx.ccx(), pat_len), expr::get_len(cx, lhs_str));
+                    }
+                    else {
+                        // The discriminant is a fat pointer
+                        let llty_str_slice = type_of::type_of(cx.ccx(), ty_str_slice).ptr_to();
+                        lhs_str = PointerCast(cx, lhs, llty_str_slice);
+                    }
+
+                    compare_str(cx, lhs_str, rhs_str, rhs_t, debug_loc)
                 },
                 _ => cx.sess().bug("only byte strings supported in compare_values"),
             },

src/librustc_trans/trans/consts.rs

@@ -75,14 +75,7 @@ pub fn const_lit(cx: &CrateContext, e: &ast::Expr, lit: &ast::Lit)
         ast::LitBool(b) => C_bool(cx, b),
         ast::LitStr(ref s, _) => C_str_slice(cx, (*s).clone()),
         ast::LitBinary(ref data) => {
-            let g = addr_of(cx, C_bytes(cx, &data[..]), "binary", e.id);
-            let base = ptrcast(g, Type::i8p(cx));
-            let prev_const = cx.const_unsized().borrow_mut()
-                               .insert(base, g);
-            assert!(prev_const.is_none() || prev_const == Some(g));
-            assert_eq!(abi::FAT_PTR_ADDR, 0);
-            assert_eq!(abi::FAT_PTR_EXTRA, 1);
-            C_struct(cx, &[base, C_uint(cx, data.len())], false)
+            addr_of(cx, C_bytes(cx, &data[..]), "binary", e.id)
         }
     }
 }

src/librustc_trans/trans/debuginfo.rs

@@ -4054,7 +4054,7 @@ fn namespace_for_item(cx: &CrateContext, def_id: ast::DefId) -> Rc<NamespaceTree
 /// .debug_gdb_scripts global is referenced, so it isn't removed by the linker.
 pub fn insert_reference_to_gdb_debug_scripts_section_global(ccx: &CrateContext) {
     if needs_gdb_debug_scripts_section(ccx) {
-        let empty = CString::new(b"").unwrap();
+        let empty = CString::new("").unwrap();
         let gdb_debug_scripts_section_global =
             get_or_insert_gdb_debug_scripts_section_global(ccx);
         unsafe {

src/librustc_typeck/check/_match.rs

@@ -48,7 +48,23 @@ pub fn check_pat<'a, 'tcx>(pcx: &pat_ctxt<'a, 'tcx>,
         ast::PatLit(ref lt) => {
             check_expr(fcx, &**lt);
             let expr_ty = fcx.expr_ty(&**lt);
-            fcx.write_ty(pat.id, expr_ty);
+
+            // Byte string patterns behave the same way as array patterns
+            // They can denote both statically and dynamically sized byte arrays
+            let mut pat_ty = expr_ty;
+            if let ast::ExprLit(ref lt) = lt.node {
+                if let ast::LitBinary(_) = lt.node {
+                    let expected_ty = structurally_resolved_type(fcx, pat.span, expected);
+                    if let ty::ty_rptr(_, mt) = expected_ty.sty {
+                        if let ty::ty_vec(_, None) = mt.ty.sty {
+                            pat_ty = ty::mk_slice(tcx, tcx.mk_region(ty::ReStatic),
+                                ty::mt{ ty: tcx.types.u8, mutbl: ast::MutImmutable })
+                        }
+                    }
+                }
+            }
+
+            fcx.write_ty(pat.id, pat_ty);
 
             // somewhat surprising: in this case, the subtyping
             // relation goes the opposite way as the other
@@ -62,7 +78,7 @@ pub fn check_pat<'a, 'tcx>(pcx: &pat_ctxt<'a, 'tcx>,
             //     &'static str <: expected
             //
             // that's equivalent to there existing a LUB.
-            demand::suptype(fcx, pat.span, expected, expr_ty);
+            demand::suptype(fcx, pat.span, expected, pat_ty);
         }
         ast::PatRange(ref begin, ref end) => {
             check_expr(fcx, &**begin);

src/librustc_typeck/check/mod.rs

@@ -2505,10 +2505,11 @@ fn check_lit<'a, 'tcx>(fcx: &FnCtxt<'a, 'tcx>,
 
     match lit.node {
         ast::LitStr(..) => ty::mk_str_slice(tcx, tcx.mk_region(ty::ReStatic), ast::MutImmutable),
-        ast::LitBinary(..) => {
-            ty::mk_slice(tcx,
-                         tcx.mk_region(ty::ReStatic),
-                         ty::mt{ ty: tcx.types.u8, mutbl: ast::MutImmutable })
+        ast::LitBinary(ref v) => {
+            ty::mk_rptr(tcx, tcx.mk_region(ty::ReStatic), ty::mt {
+                ty: ty::mk_vec(tcx, tcx.types.u8, Some(v.len())),
+                mutbl: ast::MutImmutable,
+            })
         }
         ast::LitByte(_) => tcx.types.u8,
         ast::LitChar(_) => tcx.types.char,

src/libstd/ffi/c_str.rs

@@ -58,7 +58,7 @@ use vec::Vec;
 ///     fn my_printer(s: *const libc::c_char);
 /// }
 ///
-/// let to_print = b"Hello, world!";
+/// let to_print = &b"Hello, world!"[..];
 /// let c_to_print = CString::new(to_print).unwrap();
 /// unsafe {
 ///     my_printer(c_to_print.as_ptr());
@@ -469,14 +469,14 @@ mod tests {
 
     #[test]
     fn simple() {
-        let s = CString::new(b"1234").unwrap();
+        let s = CString::new("1234").unwrap();
         assert_eq!(s.as_bytes(), b"1234");
         assert_eq!(s.as_bytes_with_nul(), b"1234\0");
     }
 
     #[test]
     fn build_with_zero1() {
-        assert!(CString::new(b"\0").is_err());
+        assert!(CString::new(&b"\0"[..]).is_err());
     }
     #[test]
     fn build_with_zero2() {
@@ -493,7 +493,7 @@ mod tests {
 
     #[test]
     fn formatted() {
-        let s = CString::new(b"12").unwrap();
+        let s = CString::new(&b"12"[..]).unwrap();
         assert_eq!(format!("{:?}", s), "\"12\"");
     }
 

src/libstd/io/buffered.rs

@@ -622,7 +622,7 @@ mod tests {
 
     #[test]
     fn test_read_line() {
-        let in_buf = b"a\nb\nc";
+        let in_buf: &[u8] = b"a\nb\nc";
         let mut reader = BufReader::with_capacity(2, in_buf);
         let mut s = String::new();
         reader.read_line(&mut s).unwrap();
@@ -640,7 +640,7 @@ mod tests {
 
     #[test]
     fn test_lines() {
-        let in_buf = b"a\nb\nc";
+        let in_buf: &[u8] = b"a\nb\nc";
         let reader = BufReader::with_capacity(2, in_buf);
         let mut it = reader.lines();
         assert_eq!(it.next(), Some(Ok("a".to_string())));