auto merge of #10018 : fhahn/rust/check-inferred-ints, r=alexcrichton

I've started working on this issue and pushed a small commit, which adds a range check for integer literals in `middle::const_eval` (no `uint` at the moment) 
At the moment, this patch is just a proof of concept, I'm not sure if there is a better function for the checks in `middle::const_eval`. This patch does not check for overflows after constant folding, eg:

    let x: i8 = 99 + 99;

Author: bors

doc/po/ja/tutorial-tasks.md.po

@@ -529,7 +529,7 @@ msgid ""
 "The basic example below illustrates this.\n"
 "~~~\n"
 "# fn make_a_sandwich() {};\n"
-"fn fib(n: uint) -> uint {\n"
+"fn fib(n: u64) -> u64 {\n"
 "    // lengthy computation returning an uint\n"
 "    12586269025\n"
 "}\n"

doc/po/tutorial-tasks.md.pot

@@ -529,7 +529,7 @@ msgid ""
 "The basic example below illustrates this.\n"
 "~~~\n"
 "# fn make_a_sandwich() {};\n"
-"fn fib(n: uint) -> uint {\n"
+"fn fib(n: u64) -> u64 {\n"
 "    // lengthy computation returning an uint\n"
 "    12586269025\n"
 "}\n"

doc/tutorial-tasks.md

@@ -273,7 +273,7 @@ later.
 The basic example below illustrates this.
 ~~~
 # fn make_a_sandwich() {};
-fn fib(n: uint) -> uint {
+fn fib(n: u64) -> u64 {
     // lengthy computation returning an uint
     12586269025
 }

src/librustc/middle/check_const.rs

@@ -199,21 +199,6 @@ pub fn check_expr(v: &mut CheckCrateVisitor,
           }
         }
     }
-    match e.node {
-        ExprLit(@codemap::Spanned {node: lit_int(v, t), _}) => {
-            if (v as u64) > ast_util::int_ty_max(
-                if t == ty_i { sess.targ_cfg.int_type } else { t }) {
-                sess.span_err(e.span, "literal out of range for its type");
-            }
-        }
-        ExprLit(@codemap::Spanned {node: lit_uint(v, t), _}) => {
-            if v > ast_util::uint_ty_max(
-                if t == ty_u { sess.targ_cfg.uint_type } else { t }) {
-                sess.span_err(e.span, "literal out of range for its type");
-            }
-        }
-        _ => ()
-    }
     visit::walk_expr(v, e, is_const);
 }
 

src/librustc/middle/lint.rs

@@ -73,6 +73,7 @@ pub enum lint {
     non_uppercase_statics,
     non_uppercase_pattern_statics,
     type_limits,
+    type_overflow,
     unused_unsafe,
 
     managed_heap_memory,
@@ -220,6 +221,14 @@ static lint_table: &'static [(&'static str, LintSpec)] = &[
         default: warn
      }),
 
+    ("type_overflow",
+     LintSpec {
+        lint: type_overflow,
+        desc: "literal out of range for its type",
+        default: warn
+     }),
+
+
     ("unused_unsafe",
      LintSpec {
         lint: unused_unsafe,
@@ -329,6 +338,9 @@ struct Context<'self> {
     // levels, this stack keeps track of the previous lint levels of whatever
     // was modified.
     lint_stack: ~[(lint, level, LintSource)],
+
+    // id of the last visited negated expression
+    negated_expr_id: ast::NodeId
 }
 
 impl<'self> Context<'self> {
@@ -522,7 +534,48 @@ fn check_type_limits(cx: &Context, e: &ast::Expr) {
                 cx.span_lint(type_limits, e.span,
                              "comparison is useless due to type limits");
             }
-        }
+        },
+        ast::ExprLit(lit) => {
+            match ty::get(ty::expr_ty(cx.tcx, e)).sty {
+                ty::ty_int(t) => {
+                    let int_type = if t == ast::ty_i {
+                        cx.tcx.sess.targ_cfg.int_type
+                    } else { t };
+                    let (min, max) = int_ty_range(int_type);
+                    let mut lit_val: i64 = match lit.node {
+                        ast::lit_int(v, _) => v,
+                        ast::lit_uint(v, _) => v as i64,
+                        ast::lit_int_unsuffixed(v) => v,
+                        _ => fail!()
+                    };
+                    if cx.negated_expr_id == e.id {
+                        lit_val *= -1;
+                    }
+                    if  lit_val < min || lit_val > max {
+                        cx.span_lint(type_overflow, e.span,
+                                     "literal out of range for its type");
+                    }
+                },
+                ty::ty_uint(t) => {
+                    let uint_type = if t == ast::ty_u {
+                        cx.tcx.sess.targ_cfg.uint_type
+                    } else { t };
+                    let (min, max) = uint_ty_range(uint_type);
+                    let lit_val: u64 = match lit.node {
+                        ast::lit_int(v, _) => v as u64,
+                        ast::lit_uint(v, _) => v,
+                        ast::lit_int_unsuffixed(v) => v as u64,
+                        _ => fail!()
+                    };
+                    if  lit_val < min || lit_val > max {
+                        cx.span_lint(type_overflow, e.span,
+                                     "literal out of range for its type");
+                    }
+                },
+
+                _ => ()
+            };
+        },
         _ => ()
     };
 
@@ -1052,11 +1105,25 @@ impl<'self> Visitor<()> for Context<'self> {
     }
 
     fn visit_expr(&mut self, e: @ast::Expr, _: ()) {
+        match e.node {
+            ast::ExprUnary(_, ast::UnNeg, expr) => {
+                // propagate negation, if the negation itself isn't negated
+                if self.negated_expr_id != e.id {
+                    self.negated_expr_id = expr.id;
+                }
+            },
+            ast::ExprParen(expr) => if self.negated_expr_id == e.id {
+                self.negated_expr_id = expr.id
+            },
+            _ => ()
+        };
+
         check_while_true_expr(self, e);
         check_stability(self, e);
         check_unused_unsafe(self, e);
         check_unnecessary_allocation(self, e);
         check_heap_expr(self, e);
+
         check_type_limits(self, e);
 
         visit::walk_expr(self, e, ());
@@ -1150,6 +1217,7 @@ pub fn check_crate(tcx: ty::ctxt,
         cur_struct_def_id: -1,
         is_doc_hidden: false,
         lint_stack: ~[],
+        negated_expr_id: -1
     };
 
     // Install default lint levels, followed by the command line levels, and

src/test/compile-fail/lint-type-limits.rs

@@ -24,11 +24,13 @@ fn bar() -> i8 {
 
 fn baz() -> bool {
     128 > bar() //~ ERROR comparison is useless due to type limits
+                //~^ WARNING literal out of range for its type
 }
 
 fn qux() {
     let mut i = 1i8;
     while 200 != i { //~ ERROR comparison is useless due to type limits
+                     //~^ WARNING literal out of range for its type
         i += 1;
     }
 }

src/test/compile-fail/lint-type-overflow.rs

@@ -0,0 +1,50 @@
+// 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(type_overflow)];
+
+fn test(x: i8) {
+    println!("x {}", x);
+}
+
+#[allow(unused_variable)]
+fn main() {
+    let x1: u8 = 255; // should be OK
+    let x1: u8 = 256; //~ error: literal out of range for its type
+
+    let x1 = 255_u8; // should be OK
+    let x1 = 256_u8; //~ error: literal out of range for its type
+
+    let x2: i8 = -128; // should be OK
+    let x1: i8 = 128; //~ error: literal out of range for its type
+    let x2: i8 = --128; //~ error: literal out of range for its type
+
+    let x3: i8 = -129; //~ error: literal out of range for its type
+    let x3: i8 = -(129); //~ error: literal out of range for its type
+    let x3: i8 = -{129}; //~ error: literal out of range for its type
+
+    test(1000); //~ error: literal out of range for its type
+
+    let x = 128_i8; //~ error: literal out of range for its type
+    let x = 127_i8; 
+    let x = -128_i8; 
+    let x = -(128_i8); 
+    let x = -129_i8; //~ error: literal out of range for its type
+
+    let x: i32 = 2147483647; // should be OK
+    let x = 2147483647_i32; // should be OK
+    let x: i32 = 2147483648; //~ error: literal out of range for its type
+    let x = 2147483648_i32; //~ error: literal out of range for its type
+    let x: i32 = -2147483648; // should be OK
+    let x = -2147483648_i32; // should be OK
+    let x: i32 = -2147483649; //~ error: literal out of range for its type
+    let x = -2147483649_i32; //~ error: literal out of range for its type
+}

src/test/compile-fail/oversized-literal.rs

@@ -8,6 +8,6 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
-// error-pattern:literal out of range
+// compile-flags: -D type-overflow
 
-fn main() { info!("{}", 300u8); }
+fn main() { info!("{}", 300u8); } //~ error: literal out of range for its type