Remove ret_style and instead check whether fn return type is bot

cc #3681

src/test/compile-fail/bad-bang-ann-3.rs

@@ -13,7 +13,7 @@
 
 fn bad_bang(i: uint) -> ! {
     return 7u;
-    //~^ ERROR expected `_|_` but found `uint`
+    //~^ ERROR expected `!` but found `uint`
 }
 
 fn main() { bad_bang(5u); }

src/test/compile-fail/bad-bang-ann.rs

@@ -13,7 +13,7 @@
 
 fn bad_bang(i: uint) -> ! {
     if i < 0u { } else { fail; }
-    //~^ ERROR expected `_|_` but found `()`
+    //~^ ERROR expected `!` but found `()`
 }
 
 fn main() { bad_bang(5u); }

src/test/compile-fail/bang-tailexpr.rs

@@ -9,6 +9,6 @@
 // except according to those terms.
 
 fn f() -> ! {
-    3i //~ ERROR expected `_|_` but found `int`
+    3i //~ ERROR expected `!` but found `int`
 }
 fn main() { }

src/test/compile-fail/closure-that-fails.rs

@@ -0,0 +1,7 @@
+fn foo(f: fn() -> !) {}
+
+fn main() {
+    // Type inference didn't use to be able to handle this:
+    foo(|| fail);
+    foo(|| 22); //~ ERROR mismatched types
+}

src/test/compile-fail/issue-897-2.rs

@@ -10,7 +10,7 @@
 
 fn g() -> ! { fail; }
 fn f() -> ! {
-    return 42i; //~ ERROR expected `_|_` but found `int`
+    return 42i; //~ ERROR expected `!` but found `int`
     g(); //~ WARNING unreachable statement
 }
 fn main() { }

src/test/compile-fail/issue-897.rs

@@ -9,7 +9,7 @@
 // except according to those terms.
 
 fn f() -> ! {
-    return 42i; //~ ERROR expected `_|_` but found `int`
+    return 42i; //~ ERROR expected `!` but found `int`
     fail; //~ WARNING unreachable statement
 }
 fn main() { }

src/test/compile-fail/loop-does-not-diverge.rs

@@ -14,7 +14,7 @@ fn forever() -> ! {
   loop {
     break;
   }
-  return 42i; //~ ERROR expected `_|_` but found `int`
+  return 42i; //~ ERROR expected `!` but found `int`
 }
 
 fn main() {