Implement mut ref/mut ref mut

Author: Jules-Bertholet

src/patterns.rs

@@ -107,18 +107,19 @@ impl Rewrite for Pat {
             }
             PatKind::Box(ref pat) => rewrite_unary_prefix(context, "box ", &**pat, shape),
             PatKind::Ident(BindingAnnotation(by_ref, mutability), ident, ref sub_pat) => {
-                let prefix = match by_ref {
-                    ByRef::Yes => "ref",
-                    ByRef::No => "",
+                let mut_prefix = format_mutability(mutability).trim();
+
+                let (ref_kw, mut_infix) = match by_ref {
+                    ByRef::Yes(rmutbl) => ("ref", format_mutability(rmutbl).trim()),
+                    ByRef::No => ("", ""),
                 };
-                let mut_infix = format_mutability(mutability).trim();
                 let id_str = rewrite_ident(context, ident);
                 let sub_pat = match *sub_pat {
                     Some(ref p) => {
                         // 2 - `@ `.
-                        let width = shape
-                            .width
-                            .checked_sub(prefix.len() + mut_infix.len() + id_str.len() + 2)?;
+                        let width = shape.width.checked_sub(
+                            mut_prefix.len() + ref_kw.len() + mut_infix.len() + id_str.len() + 2,
+                        )?;
                         let lo = context.snippet_provider.span_after(self.span, "@");
                         combine_strs_with_missing_comments(
                             context,
@@ -132,33 +133,55 @@ impl Rewrite for Pat {
                     None => "".to_owned(),
                 };
 
-                // combine prefix and mut
-                let (first_lo, first) = if !prefix.is_empty() && !mut_infix.is_empty() {
-                    let hi = context.snippet_provider.span_before(self.span, "mut");
-                    let lo = context.snippet_provider.span_after(self.span, "ref");
-                    (
+                // combine prefix and ref
+                let (first_lo, first) = match (mut_prefix.is_empty(), ref_kw.is_empty()) {
+                    (false, false) => {
+                        let lo = context.snippet_provider.span_after(self.span, "mut");
+                        let hi = context.snippet_provider.span_before(self.span, "ref");
+                        (
+                            context.snippet_provider.span_after(self.span, "ref"),
+                            combine_strs_with_missing_comments(
+                                context,
+                                mut_prefix,
+                                ref_kw,
+                                mk_sp(lo, hi),
+                                shape,
+                                true,
+                            )?,
+                        )
+                    }
+                    (false, true) => (
                         context.snippet_provider.span_after(self.span, "mut"),
-                        combine_strs_with_missing_comments(
-                            context,
-                            prefix,
-                            mut_infix,
-                            mk_sp(lo, hi),
-                            shape,
-                            true,
-                        )?,
-                    )
-                } else if !prefix.is_empty() {
-                    (
+                        mut_prefix.to_owned(),
+                    ),
+                    (true, false) => (
                         context.snippet_provider.span_after(self.span, "ref"),
-                        prefix.to_owned(),
-                    )
-                } else if !mut_infix.is_empty() {
-                    (
-                        context.snippet_provider.span_after(self.span, "mut"),
-                        mut_infix.to_owned(),
-                    )
-                } else {
-                    (self.span.lo(), "".to_owned())
+                        ref_kw.to_owned(),
+                    ),
+                    (true, true) => (self.span.lo(), "".to_owned()),
+                };
+
+                // combine result of above and mut
+                let (second_lo, second) = match (first.is_empty(), mut_infix.is_empty()) {
+                    (false, false) => {
+                        let lo = context.snippet_provider.span_after(self.span, "ref");
+                        let end_span = mk_sp(first_lo, self.span.hi());
+                        let hi = context.snippet_provider.span_before(end_span, "mut");
+                        (
+                            context.snippet_provider.span_after(end_span, "mut"),
+                            combine_strs_with_missing_comments(
+                                context,
+                                &first,
+                                mut_infix,
+                                mk_sp(lo, hi),
+                                shape,
+                                true,
+                            )?,
+                        )
+                    }
+                    (false, true) => (first_lo, first),
+                    (true, false) => unreachable!("mut_infix necessarily follows a ref"),
+                    (true, true) => (self.span.lo(), "".to_owned()),
                 };
 
                 let next = if !sub_pat.is_empty() {
@@ -177,9 +200,9 @@ impl Rewrite for Pat {
 
                 combine_strs_with_missing_comments(
                     context,
-                    &first,
+                    &second,
                     &next,
-                    mk_sp(first_lo, ident.span.lo()),
+                    mk_sp(second_lo, ident.span.lo()),
                     shape,
                     true,
                 )