Lint for unnecessary type casts

src/libextra/bitv.rs

@@ -80,7 +80,7 @@ impl SmallBitv {
             self.bits |= 1<<i;
         }
         else {
-            self.bits &= !(1<<i as uint);
+            self.bits &= !(1<<i);
         }
     }
 

src/libextra/ebml.rs

@@ -647,7 +647,7 @@ pub mod writer {
             let cur_pos = self.writer.tell();
             self.writer.seek(last_size_pos as i64, io::SeekSet);
             let size = (cur_pos as uint - last_size_pos - 4);
-            write_sized_vuint(self.writer, size as uint, 4u);
+            write_sized_vuint(self.writer, size, 4u);
             self.writer.seek(cur_pos as i64, io::SeekSet);
 
             debug!("End tag (size = {})", size);

src/libextra/test.rs

@@ -929,8 +929,8 @@ fn calc_result(desc: &TestDesc, task_succeeded: bool) -> TestResult {
 impl ToJson for Metric {
     fn to_json(&self) -> json::Json {
         let mut map = ~TreeMap::new();
-        map.insert(~"value", json::Number(self.value as f64));
-        map.insert(~"noise", json::Number(self.noise as f64));
+        map.insert(~"value", json::Number(self.value));
+        map.insert(~"noise", json::Number(self.noise));
         json::Object(map)
     }
 }
@@ -1132,15 +1132,15 @@ impl BenchHarness {
             let loop_start = precise_time_ns();
 
             for p in samples.mut_iter() {
-                self.bench_n(n as u64, |x| f(x));
+                self.bench_n(n, |x| f(x));
                 *p = self.ns_per_iter() as f64;
             };
 
             stats::winsorize(samples, 5.0);
             let summ = stats::Summary::new(samples);
 
             for p in samples.mut_iter() {
-                self.bench_n(5 * n as u64, |x| f(x));
+                self.bench_n(5 * n, |x| f(x));
                 *p = self.ns_per_iter() as f64;
             };
 

src/libextra/time.rs

@@ -767,13 +767,13 @@ pub fn strptime(s: &str, format: &str) -> Result<Tm, ~str> {
 
         let mut buf = [0];
         let c = match rdr.read(buf) {
-            Some(..) => buf[0] as u8 as char,
+            Some(..) => buf[0] as char,
             None => break
         };
         match c {
             '%' => {
                 let ch = match rdr.read(buf) {
-                    Some(..) => buf[0] as u8 as char,
+                    Some(..) => buf[0] as char,
                     None => break
                 };
                 match parse_type(s, pos, ch, &mut tm) {

src/librustc/middle/lint.rs

@@ -41,6 +41,10 @@ use middle::typeck;
 use middle::pat_util;
 use metadata::csearch;
 use util::ppaux::{ty_to_str};
+use std::to_str::ToStr;
+
+use middle::typeck::infer;
+use middle::typeck::astconv::{ast_ty_to_ty, AstConv};
 
 use std::cmp;
 use std::hashmap::HashMap;
@@ -91,6 +95,7 @@ pub enum lint {
     unused_mut,
     unnecessary_allocation,
     dead_code,
+    unnecessary_typecast,
 
     missing_doc,
     unreachable_code,
@@ -267,6 +272,13 @@ static lint_table: &'static [(&'static str, LintSpec)] = &[
         default: warn
     }),
 
+    ("unnecessary_typecast",
+     LintSpec {
+        lint: unnecessary_typecast,
+        desc: "detects unnecessary type casts, that can be removed",
+        default: allow,
+    }),
+
     ("unused_mut",
      LintSpec {
         lint: unused_mut,
@@ -336,7 +348,6 @@ static lint_table: &'static [(&'static str, LintSpec)] = &[
         desc: "unknown features found in crate-level #[feature] directives",
         default: deny,
     }),
-
      ("unknown_crate_type",
      LintSpec {
          lint: unknown_crate_type,
@@ -569,6 +580,37 @@ fn check_while_true_expr(cx: &Context, e: &ast::Expr) {
         _ => ()
     }
 }
+impl<'a> AstConv for Context<'a>{
+    fn tcx(&self) -> ty::ctxt { self.tcx }
+
+    fn get_item_ty(&self, id: ast::DefId) -> ty::ty_param_bounds_and_ty {
+        ty::lookup_item_type(self.tcx, id)
+    }
+
+    fn get_trait_def(&self, id: ast::DefId) -> @ty::TraitDef {
+        ty::lookup_trait_def(self.tcx, id)
+    }
+
+    fn ty_infer(&self, _span: Span) -> ty::t {
+        let infcx: @infer::InferCtxt = infer::new_infer_ctxt(self.tcx);
+        infcx.next_ty_var()
+    }
+}
+
+
+fn check_unused_casts(cx: &Context, e: &ast::Expr) {
+    return match e.node {
+        ast::ExprCast(expr, ty) => {
+            let infcx: @infer::InferCtxt = infer::new_infer_ctxt(cx.tcx);
+            let t_t = ast_ty_to_ty(cx, &infcx, ty);
+            if  ty::get(ty::expr_ty(cx.tcx, expr)).sty == ty::get(t_t).sty {
+                cx.span_lint(unnecessary_typecast, ty.span,
+                             "unnecessary type cast");
+            }
+        }
+        _ => ()
+    };
+}
 
 fn check_type_limits(cx: &Context, e: &ast::Expr) {
     return match e.node {
@@ -1361,6 +1403,7 @@ impl<'a> Visitor<()> for Context<'a> {
         check_heap_expr(self, e);
 
         check_type_limits(self, e);
+        check_unused_casts(self, e);
 
         visit::walk_expr(self, e, ());
     }

src/libstd/cleanup.rs

@@ -42,7 +42,7 @@ unsafe fn each_live_alloc(read_next_before: bool,
         let next_before = (*alloc).next;
         let uniq = (*alloc).ref_count == managed::RC_MANAGED_UNIQUE;
 
-        if !f(alloc as *mut raw::Box<()>, uniq) {
+        if !f(alloc, uniq) {
             return false;
         }
 

src/libstd/io/mod.rs

@@ -725,7 +725,7 @@ pub trait Reader {
     ///
     /// `u64`s are 8 bytes long.
     fn read_be_u64(&mut self) -> u64 {
-        self.read_be_uint_n(8) as u64
+        self.read_be_uint_n(8)
     }
 
     /// Reads a big-endian `u32`.
@@ -746,7 +746,7 @@ pub trait Reader {
     ///
     /// `i64`s are 8 bytes long.
     fn read_be_i64(&mut self) -> i64 {
-        self.read_be_int_n(8) as i64
+        self.read_be_int_n(8)
     }
 
     /// Reads a big-endian `i32`.
@@ -785,7 +785,7 @@ pub trait Reader {
     ///
     /// `u64`s are 8 bytes long.
     fn read_le_u64(&mut self) -> u64 {
-        self.read_le_uint_n(8) as u64
+        self.read_le_uint_n(8)
     }
 
     /// Reads a little-endian `u32`.
@@ -806,7 +806,7 @@ pub trait Reader {
     ///
     /// `i64`s are 8 bytes long.
     fn read_le_i64(&mut self) -> i64 {
-        self.read_le_int_n(8) as i64
+        self.read_le_int_n(8)
     }
 
     /// Reads a little-endian `i32`.
@@ -846,7 +846,7 @@ pub trait Reader {
     /// `u8`s are 1 byte.
     fn read_u8(&mut self) -> u8 {
         match self.read_byte() {
-            Some(b) => b as u8,
+            Some(b) => b,
             None => 0
         }
     }

src/libstd/io/net/ip.rs

@@ -153,11 +153,11 @@ impl<'a> Parser<'a> {
             let c = c as u8;
             // assuming radix is either 10 or 16
             if c >= '0' as u8 && c <= '9' as u8 {
-                Some((c - '0' as u8) as u8)
+                Some(c - '0' as u8)
             } else if radix > 10 && c >= 'a' as u8 && c < 'a' as u8 + (radix - 10) {
-                Some((c - 'a' as u8 + 10) as u8)
+                Some(c - 'a' as u8 + 10)
             } else if radix > 10 && c >= 'A' as u8 && c < 'A' as u8 + (radix - 10) {
-                Some((c - 'A' as u8 + 10) as u8)
+                Some(c - 'A' as u8 + 10)
             } else {
                 None
             }

src/libstd/io/stdio.rs

@@ -209,7 +209,7 @@ impl Reader for StdReader {
                 io_error::cond.raise(standard_error(EndOfFile));
                 None
             }
-            Ok(amt) => Some(amt as uint),
+            Ok(amt) => Some(amt),
             Err(e) => {
                 io_error::cond.raise(e);
                 None

src/libstd/num/strconv.rs

@@ -344,7 +344,7 @@ pub fn float_to_str_bytes_common<T:NumCast+Zero+One+Eq+Ord+Float+Round+
         // round the remaining ones.
         if limit_digits && dig == digit_count {
             let ascii2value = |chr: u8| {
-                char::to_digit(chr as char, radix).unwrap() as uint
+                char::to_digit(chr as char, radix).unwrap()
             };
             let value2ascii = |val: uint| {
                 char::from_digit(val, radix).unwrap() as u8

src/libstd/rand/distributions/normal.rs

@@ -32,7 +32,7 @@ impl Rand for StandardNormal {
     fn rand<R:Rng>(rng: &mut R) -> StandardNormal {
         #[inline]
         fn pdf(x: f64) -> f64 {
-            ((-x*x/2.0) as f64).exp()
+            (-x*x/2.0).exp()
         }
         #[inline]
         fn zero_case<R:Rng>(rng: &mut R, u: f64) -> f64 {

src/libstd/rt/global_heap.rs

@@ -76,7 +76,7 @@ pub unsafe fn closure_exchange_malloc(td: *c_char, size: uintptr_t) -> *c_char {
     assert!(td.is_not_null());
 
     let total_size = get_box_size(size, (*td).align);
-    let p = malloc_raw(total_size as uint);
+    let p = malloc_raw(total_size);
 
     let alloc = p as *mut raw::Box<()>;
     (*alloc).type_desc = td;

src/libstd/str.rs

@@ -901,7 +901,7 @@ pub fn utf16_chars(v: &[u16], f: |char|) {
             let mut c: u32 = (u - 0xD800_u16) as u32;
             c = c << 10;
             c |= (u2 - 0xDC00_u16) as u32;
-            c |= 0x1_0000_u32 as u32;
+            c |= 0x1_0000_u32;
             f(unsafe { cast::transmute(c) });
             i += 2u;
         }
@@ -987,7 +987,7 @@ pub mod raw {
     /// Create a Rust string from a *u8 buffer of the given length
     pub unsafe fn from_buf_len(buf: *u8, len: uint) -> ~str {
         let mut v: ~[u8] = vec::with_capacity(len);
-        ptr::copy_memory(v.as_mut_ptr(), buf as *u8, len);
+        ptr::copy_memory(v.as_mut_ptr(), buf, len);
         v.set_len(len);
 
         assert!(is_utf8(v));

src/libstd/unstable/mutex.rs

@@ -66,8 +66,8 @@ impl Mutex {
     /// Creates a new mutex, with the lock/condition variable pre-initialized
     pub unsafe fn new() -> Mutex {
         Mutex {
-            lock: atomics::AtomicUint::new(imp::init_lock() as uint),
-            cond: atomics::AtomicUint::new(imp::init_cond() as uint),
+            lock: atomics::AtomicUint::new(imp::init_lock()),
+            cond: atomics::AtomicUint::new(imp::init_cond()),
         }
     }
 

src/test/compile-fail/lint-unnecessary-casts.rs

@@ -0,0 +1,24 @@
+// 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.
+
+#[forbid(unnecessary_typecast)];
+
+fn foo_i32(_: i32) {}
+
+fn foo_u64(a: u64) {
+    let b: i32 = a as i32;
+    foo_i32(b as i32); //~ ERROR: unnecessary type cast
+}
+
+fn main() {
+    let x: u64 = 1;
+    let y: u64 = x as u64; //~ ERROR: unnecessary type cast
+    foo_u64(y as u64); //~ ERROR: unnecessary type cast
+}