move NeedlessReturn pass out to its own module and rename to ReturnPass

src/misc.rs

@@ -270,75 +270,6 @@ fn is_str_arg(cx: &Context, args: &[P<Expr>]) -> bool {
         walk_ptrs_ty(cx.tcx.expr_ty(&*args[0])).sty { true } else { false }
 }
 
-declare_lint!(pub NEEDLESS_RETURN, Warn,
-              "Warn on using a return statement where an expression would be enough");
-
-#[derive(Copy,Clone)]
-pub struct NeedlessReturn;
-
-impl NeedlessReturn {
-    // Check the final stmt or expr in a block for unnecessary return.
-    fn check_block_return(&mut self, cx: &Context, block: &Block) {
-        if let Some(ref expr) = block.expr {
-            self.check_final_expr(cx, expr);
-        } else if let Some(stmt) = block.stmts.last() {
-            if let StmtSemi(ref expr, _) = stmt.node {
-                if let ExprRet(Some(ref inner)) = expr.node {
-                    self.emit_lint(cx, (expr.span, inner.span));
-                }
-            }
-        }
-    }
-
-    // Check a the final expression in a block if it's a return.
-    fn check_final_expr(&mut self, cx: &Context, expr: &Expr) {
-        match expr.node {
-            // simple return is always "bad"
-            ExprRet(Some(ref inner)) => {
-                self.emit_lint(cx, (expr.span, inner.span));
-            }
-            // a whole block? check it!
-            ExprBlock(ref block) => {
-                self.check_block_return(cx, block);
-            }
-            // an if/if let expr, check both exprs
-            // note, if without else is going to be a type checking error anyways
-            // (except for unit type functions) so we don't match it
-            ExprIf(_, ref ifblock, Some(ref elsexpr)) |
-            ExprIfLet(_, _, ref ifblock, Some(ref elsexpr)) => {
-                self.check_block_return(cx, ifblock);
-                self.check_final_expr(cx, elsexpr);
-            }
-            // a match expr, check all arms
-            ExprMatch(_, ref arms, _) => {
-                for arm in arms {
-                    self.check_final_expr(cx, &*arm.body);
-                }
-            }
-            _ => { }
-        }
-    }
-
-    fn emit_lint(&mut self, cx: &Context, spans: (Span, Span)) {
-        span_lint(cx, NEEDLESS_RETURN, spans.0, &format!(
-            "unneeded return statement. Consider using {} \
-             without the trailing semicolon",
-            snippet(cx, spans.1, "..")))
-    }
-}
-
-impl LintPass for NeedlessReturn {
-    fn get_lints(&self) -> LintArray {
-        lint_array!(NEEDLESS_RETURN)
-    }
-
-    fn check_fn(&mut self, cx: &Context, _: FnKind, _: &FnDecl,
-                block: &Block, _: Span, _: ast::NodeId) {
-        self.check_block_return(cx, block);
-    }
-}
-
-
 declare_lint!(pub MODULO_ONE, Warn, "Warn on expressions that include % 1, which is always 0");
 
 #[derive(Copy,Clone)]