Add remove nested parens option

Configurations.md

@@ -1270,6 +1270,28 @@ fn dolor() -> usize {}
 fn adipiscing() -> usize {}
 ```
 
+## `remove_nested_parens`
+
+Remove nested parens.
+
+- **Defalut value**: `false`,
+- **Possible values**: `true`, `false`
+- **Stable**: No
+
+#### `false` (default):
+```rust
+fn main() {
+    ((((foo()))));
+}
+```
+
+#### `true`:
+```rust
+fn main() {
+    (foo());
+}
+```
+
 
 ## `reorder_imports`
 

src/config/mod.rs

@@ -106,6 +106,8 @@ create_config! {
         "Maximum number of blank lines which can be put between items.";
     blank_lines_lower_bound: usize, 0, false,
         "Minimum number of blank lines which must be put between items.";
+    remove_nested_parens: bool, false, false,
+        "Remove nested parens.";
 
     // Options that can change the source code beyond whitespace/blocks (somewhat linty things)
     merge_derives: bool, true, true, "Merge multiple `#[derive(...)]` into a single one";

src/expr.rs

@@ -1474,6 +1474,7 @@ fn rewrite_paren(
     // Extract comments within parens.
     let mut pre_comment;
     let mut post_comment;
+    let remove_nested_parens = context.config.remove_nested_parens();
     loop {
         // 1 = "(" or ")"
         let pre_span = mk_sp(span.lo() + BytePos(1), subexpr.span.lo());
@@ -1483,7 +1484,7 @@ fn rewrite_paren(
 
         // Remove nested parens if there are no comments.
         if let ast::ExprKind::Paren(ref subsubexpr) = subexpr.node {
-            if pre_comment.is_empty() && post_comment.is_empty() {
+            if remove_nested_parens && pre_comment.is_empty() && post_comment.is_empty() {
                 span = subexpr.span;
                 subexpr = subsubexpr;
                 continue;

tests/source/configs/remove_nested_parens/remove_nested_parens.rs

@@ -0,0 +1,5 @@
+// rustfmt-remove_nested_parens: true
+
+fn main() {
+    ((((((foo()))))));
+}

tests/source/expr.rs

@@ -1,5 +1,6 @@
 // rustfmt-normalize_comments: true
 // rustfmt-wrap_comments: true
+// rustfmt-remove_nested_parens: true
 // Test expressions
 
 fn foo() -> bool {

tests/source/paren.rs

@@ -1,4 +1,4 @@
-// Remove nested parens.
+// rustfmt-remove_nested_parens: true
 
 fn main() {
     let x = (((1)));

tests/target/configs/remove_nested_parens/remove_nested_parens.rs

@@ -0,0 +1,5 @@
+// rustfmt-remove_nested_parens: true
+
+fn main() {
+    (foo());
+}

tests/target/expr.rs

@@ -1,5 +1,6 @@
 // rustfmt-normalize_comments: true
 // rustfmt-wrap_comments: true
+// rustfmt-remove_nested_parens: true
 // Test expressions
 
 fn foo() -> bool {

tests/target/paren.rs

@@ -1,4 +1,4 @@
-// Remove nested parens.
+// rustfmt-remove_nested_parens: true
 
 fn main() {
     let x = (1);