Allow empty tuple pattern

Author: topecongiro

src/patterns.rs

@@ -288,7 +288,7 @@ fn rewrite_tuple_pat(
     }
 
     if pat_vec.is_empty() {
-        return Some(format!("{}()", try_opt!(path_str)));
+        return Some(format!("{}()", path_str.unwrap_or(String::new())));
     }
 
     let wildcard_suffix_len = count_wildcard_suffix_len(context, &pat_vec, span, shape);

tests/source/pattern.rs

@@ -42,3 +42,9 @@ impl<'a,'b> ResolveGeneratedContentFragmentMutator<'a,'b> {
 fn issue_1319() {
     if let (Event { .. }, .. ) = ev_state {}
 }
+
+fn issue_1874() {
+    if let Some(()) = x {
+y
+    }
+}

tests/target/pattern.rs

@@ -57,3 +57,9 @@ impl<'a, 'b> ResolveGeneratedContentFragmentMutator<'a, 'b> {
 fn issue_1319() {
     if let (Event { .. }, ..) = ev_state {}
 }
+
+fn issue_1874() {
+    if let Some(()) = x {
+        y
+    }
+}