Fix overlong function signature (#1089)

* Fix issue-1049

* Add testcase suggested by pepyakin

* Fix last commit

* Handle special case

* Remove debugging println

* Fix grammar in comment

* Change word in comment

* Add test for long func without ret type

* Add one more test

Author: dawirstejeck

src/items.rs

@@ -1369,10 +1369,21 @@ fn rewrite_fn_base(context: &RewriteContext,
             FnArgLayoutStyle::Block if put_args_in_block => false,
             FnArgLayoutStyle::BlockAlways => false,
             _ => {
-                // If we've already gone multi-line, or the return type would push
-                // over the max width, then put the return type on a new line.
-                result.contains("\n") || multi_line_ret_str ||
-                result.len() + indent.width() + ret_str_len > context.config.max_width
+                // If we've already gone multi-line, or the return type would push over the max
+                // width, then put the return type on a new line. With the +1 for the signature
+                // length an additional space between the closing parenthesis of the argument and
+                // the arrow '->' is considered.
+                let mut sig_length = result.len() + indent.width() + ret_str_len + 1;
+
+                // If there is no where clause, take into account the space after the return type
+                // and the brace.
+                if where_clause.predicates.is_empty() {
+                    sig_length += 2;
+                }
+
+                let overlong_sig = sig_length > context.config.max_width;
+
+                result.contains("\n") || multi_line_ret_str || overlong_sig
             }
         };
         let ret_indent = if ret_should_indent {
@@ -1400,10 +1411,8 @@ fn rewrite_fn_base(context: &RewriteContext,
         if multi_line_ret_str {
             // Now that we know the proper indent and width, we need to
             // re-layout the return type.
-
             let budget = try_opt!(context.config.max_width.checked_sub(ret_indent.width()));
-            let ret_str = try_opt!(fd.output
-                .rewrite(context, budget, ret_indent));
+            let ret_str = try_opt!(fd.output.rewrite(context, budget, ret_indent));
             result.push_str(&ret_str);
         } else {
             result.push_str(&ret_str);

tests/source/issue-1049.rs

@@ -0,0 +1,16 @@
+// Test overlong function signature
+pub unsafe fn reborrow_mut(&mut X: Abcde) -> Handle<NodeRef<marker::Mut, K, V, NodeType>, HandleType> {
+}
+
+pub fn merge(mut X: Abcdef) -> Handle<NodeRef<marker::Mut<'a>, K, V, marker::Internal>, marker::Edge> {
+}
+
+impl Handle {
+    pub fn merge(a: Abcd) -> Handle<NodeRef<marker::Mut<'a>, K, V, marker::Internal>, marker::Edge> {
+    }
+}
+
+// Long function without return type that should not be reformated.
+fn veeeeeeeeeeeeeeeeeeeeery_long_name(a: FirstTypeeeeeeeeee, b: SecondTypeeeeeeeeeeeeeeeeeeeeeee) {}
+
+fn veeeeeeeeeeeeeeeeeeeeeery_long_name(a: FirstTypeeeeeeeeee, b: SecondTypeeeeeeeeeeeeeeeeeeeeeee) {}

tests/target/issue-1049.rs

@@ -0,0 +1,21 @@
+// Test overlong function signature
+pub unsafe fn reborrow_mut(&mut X: Abcde)
+                           -> Handle<NodeRef<marker::Mut, K, V, NodeType>, HandleType> {
+}
+
+pub fn merge(mut X: Abcdef)
+             -> Handle<NodeRef<marker::Mut<'a>, K, V, marker::Internal>, marker::Edge> {
+}
+
+impl Handle {
+    pub fn merge(a: Abcd)
+                 -> Handle<NodeRef<marker::Mut<'a>, K, V, marker::Internal>, marker::Edge> {
+    }
+}
+
+// Long function without return type that should not be reformated.
+fn veeeeeeeeeeeeeeeeeeeeery_long_name(a: FirstTypeeeeeeeeee, b: SecondTypeeeeeeeeeeeeeeeeeeeeeee) {}
+
+fn veeeeeeeeeeeeeeeeeeeeeery_long_name(a: FirstTypeeeeeeeeee,
+                                       b: SecondTypeeeeeeeeeeeeeeeeeeeeeee) {
+}