chore: apply pattern parsing changes

Author: calebcartwright

src/formatting/macros.rs

@@ -131,7 +131,7 @@ fn parse_macro_arg<'a, 'b: 'a>(parser: &'a mut Parser<'b>) -> Option<MacroArg> {
     );
     parse_macro_arg!(
         Pat,
-        |parser: &mut rustc_parse::parser::Parser<'b>| parser.parse_pat(None),
+        |parser: &mut rustc_parse::parser::Parser<'b>| parser.parse_pat_no_top_alt(None),
         |x: ptr::P<ast::Pat>| Some(x)
     );
     // `parse_item` returns `Option<ptr::P<ast::Item>>`.

src/formatting/matches.rs

@@ -19,7 +19,7 @@ use crate::formatting::{
     spanned::Spanned,
     utils::{
         contains_skip, extra_offset, first_line_width, inner_attributes, last_line_extendable,
-        mk_sp, semicolon_for_expr, trimmed_last_line_width, unicode_str_width,
+        mk_sp, mk_sp_lo_plus_one, semicolon_for_expr, trimmed_last_line_width, unicode_str_width,
     },
 };
 
@@ -164,17 +164,14 @@ fn arm_comma(config: &Config, body: &ast::Expr, is_last: bool) -> &'static str {
 fn collect_beginning_verts(
     context: &RewriteContext<'_>,
     arms: &[ast::Arm],
-    span: Span,
 ) -> Vec<Option<BytePos>> {
-    let mut beginning_verts = Vec::with_capacity(arms.len());
-    let mut lo = context.snippet_provider.span_after(span, "{");
-    for arm in arms {
-        let hi = arm.pat.span.lo();
-        let missing_span = mk_sp(lo, hi);
-        beginning_verts.push(context.snippet_provider.opt_span_before(missing_span, "|"));
-        lo = arm.span().hi();
-    }
-    beginning_verts
+    arms.iter()
+        .map(|a| {
+            context
+                .snippet_provider
+                .opt_span_before(mk_sp_lo_plus_one(a.pat.span.lo()), "|")
+        })
+        .collect()
 }
 
 fn rewrite_match_arms(
@@ -192,7 +189,7 @@ fn rewrite_match_arms(
     let is_last_iter = repeat(false)
         .take(arm_len.saturating_sub(1))
         .chain(repeat(true));
-    let beginning_verts = collect_beginning_verts(context, arms, span);
+    let beginning_verts = collect_beginning_verts(context, arms);
     let items = itemize_list(
         context.snippet_provider,
         arms.iter()