Print missing semicolon warning for type-inferred ints

src/librustc/middle/liveness.rs

@@ -1483,7 +1483,14 @@ impl<'a, 'tcx> Liveness<'a, 'tcx> {
                         None if !body.stmts.is_empty() =>
                             match body.stmts.first().unwrap().node {
                                 hir::StmtSemi(ref e, _) => {
-                                    self.ir.tcx.expr_ty(&**e) == t_ret
+                                    match (&self.ir.tcx.expr_ty(&**e).sty, &t_ret.sty) {
+                                        // Type inference causes unsuffixed integer literals
+                                        // to be evaluated as i32 values. We still want to
+                                        // inform the user of a semicolon in this case.
+                                        (&ty::TyInt(ast::TyI32), &ty::TyInt(..)) => true,
+                                        (&ty::TyInt(ast::TyI32), &ty::TyUint(..)) => true,
+                                        (a, b) => (a == b),
+                                    }
                                 },
                                 _ => false
                             },

src/test/compile-fail/missing-semicolon.rs

@@ -0,0 +1,17 @@
+// Copyright 2012 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.
+
+// error-pattern:consider removing this semicolon
+
+fn foo() -> u16 {
+    1234;
+}
+
+fn main() { }