Forbid method chain to get combined if it uses multi line.

If the method chain goes multi line before the last element, disallow combining
the method chain.

src/chains.rs

@@ -252,6 +252,9 @@ pub fn rewrite_chain(expr: &ast::Expr, context: &RewriteContext, shape: Shape) -
         String::new()
     } else {
         // Use new lines.
+        if context.force_one_line_chain {
+            return None;
+        }
         format!("\n{}", nested_shape.indent.to_string(context.config))
     };
 

src/expr.rs

@@ -1784,6 +1784,11 @@ fn try_overflow_last_arg(context: &RewriteContext,
     // Replace the last item with its first line to see if it fits with
     // first arguments.
     let (orig_last, placeholder) = if overflow_last {
+        let mut context = context.clone();
+        match args[args.len() - 1].node {
+            ast::ExprKind::MethodCall(..) => context.force_one_line_chain = true,
+            _ => (),
+        }
         last_arg_shape(&context, &item_vec, shape).map_or((None, None), |arg_shape| {
             rewrite_last_arg_with_overflow(&context,
                                            &args[args.len() - 1],

src/rewrite.rs

@@ -32,6 +32,8 @@ pub struct RewriteContext<'a> {
     // When `format_if_else_cond_comment` is true, unindent the comment on top
     // of the `else` or `else if`.
     pub is_if_else_block: bool,
+    // When rewriting chain, veto going multi line except the last element
+    pub force_one_line_chain: bool,
 }
 
 impl<'a> RewriteContext<'a> {

src/visitor.rs

@@ -629,6 +629,7 @@ pub fn get_context(&self) -> RewriteContext {
             inside_macro: false,
             use_block: false,
             is_if_else_block: false,
+            force_one_line_chain: false,
         }
     }
 }