Wrap let-else expression in paren if needed

Author: dtolnay

src/classify.rs

@@ -1,15 +1,9 @@
 use crate::expr::Expr;
-#[cfg(feature = "parsing")]
 use crate::generics::TypeParamBound;
-#[cfg(feature = "parsing")]
 use crate::path::{Path, PathArguments};
-#[cfg(feature = "parsing")]
 use crate::punctuated::Punctuated;
-#[cfg(feature = "parsing")]
 use crate::ty::{ReturnType, Type};
-#[cfg(feature = "parsing")]
 use proc_macro2::{Delimiter, TokenStream, TokenTree};
-#[cfg(feature = "parsing")]
 use std::ops::ControlFlow;
 
 pub(crate) fn requires_terminator(expr: &Expr) -> bool {
@@ -57,7 +51,6 @@ pub(crate) fn requires_terminator(expr: &Expr) -> bool {
 }
 
 /// Whether the expression's last token is `}`.
-#[cfg(feature = "parsing")]
 pub(crate) fn expr_trailing_brace(mut expr: &Expr) -> bool {
     loop {
         match expr {
@@ -116,7 +109,6 @@ pub(crate) fn expr_trailing_brace(mut expr: &Expr) -> bool {
     }
 }
 
-#[cfg(feature = "parsing")]
 fn type_trailing_brace(mut ty: &Type) -> bool {
     fn last_type_in_path(path: &Path) -> Option<&Type> {
         match &path.segments.last().unwrap().arguments {
@@ -174,7 +166,6 @@ fn type_trailing_brace(mut ty: &Type) -> bool {
     }
 }
 
-#[cfg(feature = "parsing")]
 fn tokens_trailing_brace(tokens: &TokenStream) -> bool {
     if let Some(TokenTree::Group(last)) = tokens.clone().into_iter().last() {
         last.delimiter() == Delimiter::Brace

src/stmt.rs

@@ -411,8 +411,10 @@ pub(crate) mod parsing {
 
 #[cfg(feature = "printing")]
 mod printing {
+    use crate::classify;
     use crate::expr;
     use crate::stmt::{Block, Local, Stmt, StmtMacro};
+    use crate::token;
     use proc_macro2::TokenStream;
     use quote::{ToTokens, TokenStreamExt};
 
@@ -448,7 +450,11 @@ mod printing {
             self.pat.to_tokens(tokens);
             if let Some(init) = &self.init {
                 init.eq_token.to_tokens(tokens);
-                init.expr.to_tokens(tokens);
+                if init.diverge.is_some() && classify::expr_trailing_brace(&init.expr) {
+                    token::Paren::default().surround(tokens, |tokens| init.expr.to_tokens(tokens));
+                } else {
+                    init.expr.to_tokens(tokens);
+                }
                 if let Some((else_token, diverge)) = &init.diverge {
                     else_token.to_tokens(tokens);
                     diverge.to_tokens(tokens);