Raise precedence of closure that has explicit return type

compiler/rustc_ast/src/ast.rs

@@ -1316,9 +1316,15 @@ impl Expr {
     }
 
     pub fn precedence(&self) -> ExprPrecedence {
-        match self.kind {
+        match &self.kind {
+            ExprKind::Closure(closure) => {
+                match closure.fn_decl.output {
+                    FnRetTy::Default(_) => ExprPrecedence::Jump,
+                    FnRetTy::Ty(_) => ExprPrecedence::Unambiguous,
+                }
+            }
+
             ExprKind::Break(..)
-            | ExprKind::Closure(..)
             | ExprKind::Continue(..)
             | ExprKind::Ret(..)
             | ExprKind::Yield(..)

compiler/rustc_hir/src/hir.rs

@@ -1696,9 +1696,15 @@ pub struct Expr<'hir> {
 
 impl Expr<'_> {
     pub fn precedence(&self) -> ExprPrecedence {
-        match self.kind {
+        match &self.kind {
+            ExprKind::Closure(closure) => {
+                match closure.fn_decl.output {
+                    FnRetTy::DefaultReturn(_) => ExprPrecedence::Jump,
+                    FnRetTy::Return(_) => ExprPrecedence::Unambiguous,
+                }
+            }
+
             ExprKind::Break(..)
-            | ExprKind::Closure { .. }
             | ExprKind::Continue(..)
             | ExprKind::Ret(..)
             | ExprKind::Yield(..)
@@ -1741,7 +1747,7 @@ impl Expr<'_> {
             | ExprKind::Type(..)
             | ExprKind::Err(_) => ExprPrecedence::Unambiguous,
 
-            ExprKind::DropTemps(ref expr, ..) => expr.precedence(),
+            ExprKind::DropTemps(expr, ..) => expr.precedence(),
         }
     }
 

tests/ui-fulldeps/pprust-parenthesis-insertion.rs

@@ -74,7 +74,7 @@ static EXPRS: &[&str] = &[
     "|| return break 2",
     "return break || 2",
     // Closures with a return type have especially high precedence.
-    "(|| -> T { x }) + 1", // FIXME: no parenthesis needed.
+    "|| -> T { x } + 1",
     "(|| { x }) + 1",
     // These mean different things.
     "if let _ = true && false {}",