From 68854b798ebda70014985d26722e7f6820254658 Mon Sep 17 00:00:00 2001
From: David Tolnay <dtolnay@gmail.com>
Date: Sun, 12 May 2024 13:24:36 -0700
Subject: [PATCH 1/2] Add AST pretty-printer tests for let-else

---
 tests/ui/macros/stringify.rs                      | 15 +++++++++++++++
 .../{pretty-let-else.rs => let-else-hir.rs}       |  0
 ...pretty-let-else.stdout => let-else-hir.stdout} |  0
 tests/ui/unpretty/let-else.rs                     | 11 +++++++++++
 tests/ui/unpretty/let-else.stdout                 | 15 +++++++++++++++
 5 files changed, 41 insertions(+)
 rename tests/ui/unpretty/{pretty-let-else.rs => let-else-hir.rs} (100%)
 rename tests/ui/unpretty/{pretty-let-else.stdout => let-else-hir.stdout} (100%)
 create mode 100644 tests/ui/unpretty/let-else.rs
 create mode 100644 tests/ui/unpretty/let-else.stdout

diff --git a/tests/ui/macros/stringify.rs b/tests/ui/macros/stringify.rs
index 472cb4d417be8..6b215ba525deb 100644
--- a/tests/ui/macros/stringify.rs
+++ b/tests/ui/macros/stringify.rs
@@ -675,6 +675,11 @@ fn test_stmt() {
         "let (a, b): (u32, u32) = (1, 2);",
         "let (a, b): (u32, u32) = (1, 2)"
     );
+    c2!(stmt,
+        [ let _ = f() else { return; } ],
+        "let _ = f() else { return; };",
+        "let _ = f() else { return; }",
+    );
     macro_rules! c2_let_expr_minus_one {
         ([ $expr:expr ], $stmt_expected:expr, $tokens_expected:expr $(,)?) => {
             c2!(stmt, [ let _ = $expr - 1 ], $stmt_expected, $tokens_expected);
@@ -685,6 +690,16 @@ fn test_stmt() {
         "let _ = match void {} - 1;",
         "let _ = match void {} - 1",
     );
+    macro_rules! c2_let_expr_else_return {
+        ([ $expr:expr ], $stmt_expected:expr, $tokens_expected:expr $(,)?) => {
+            c2!(stmt, [ let _ = $expr else { return; } ], $stmt_expected, $tokens_expected);
+        };
+    }
+    c2_let_expr_else_return!(
+        [ f() ],
+        "let _ = f() else { return; };",
+        "let _ = f() else { return; }",
+    );
 
     // StmtKind::Item
     c1!(stmt, [ struct S; ], "struct S;");
diff --git a/tests/ui/unpretty/pretty-let-else.rs b/tests/ui/unpretty/let-else-hir.rs
similarity index 100%
rename from tests/ui/unpretty/pretty-let-else.rs
rename to tests/ui/unpretty/let-else-hir.rs
diff --git a/tests/ui/unpretty/pretty-let-else.stdout b/tests/ui/unpretty/let-else-hir.stdout
similarity index 100%
rename from tests/ui/unpretty/pretty-let-else.stdout
rename to tests/ui/unpretty/let-else-hir.stdout
diff --git a/tests/ui/unpretty/let-else.rs b/tests/ui/unpretty/let-else.rs
new file mode 100644
index 0000000000000..4db6eca99b18f
--- /dev/null
+++ b/tests/ui/unpretty/let-else.rs
@@ -0,0 +1,11 @@
+//@ compile-flags: -Zunpretty=expanded
+//@ check-pass
+
+macro_rules! expr {
+    ($e:expr) => { $e };
+}
+
+fn main() {
+    let _ = expr!(1 + 1) else { return; };
+    let _ = expr!(loop {}) else { return; };
+}
diff --git a/tests/ui/unpretty/let-else.stdout b/tests/ui/unpretty/let-else.stdout
new file mode 100644
index 0000000000000..5f6972cd4295f
--- /dev/null
+++ b/tests/ui/unpretty/let-else.stdout
@@ -0,0 +1,15 @@
+#![feature(prelude_import)]
+#![no_std]
+#[prelude_import]
+use ::std::prelude::rust_2015::*;
+#[macro_use]
+extern crate std;
+//@ compile-flags: -Zunpretty=expanded
+//@ check-pass
+
+macro_rules! expr { ($e:expr) => { $e }; }
+
+fn main() {
+    let _ = 1 + 1 else { return; };
+    let _ = loop {} else { return; };
+}

From 94cc82c088b9301dc4dcf84ce127a64bbd77dddf Mon Sep 17 00:00:00 2001
From: David Tolnay <dtolnay@gmail.com>
Date: Sun, 12 May 2024 13:39:43 -0700
Subject: [PATCH 2/2] Pretty-print let-else with added parenthesization when
 needed

---
 compiler/rustc_ast_pretty/src/pprust/state.rs | 6 +++++-
 tests/ui/unpretty/let-else.stdout             | 2 +-
 2 files changed, 6 insertions(+), 2 deletions(-)

diff --git a/compiler/rustc_ast_pretty/src/pprust/state.rs b/compiler/rustc_ast_pretty/src/pprust/state.rs
index 2c176828c841f..b7bdb2e14a6da 100644
--- a/compiler/rustc_ast_pretty/src/pprust/state.rs
+++ b/compiler/rustc_ast_pretty/src/pprust/state.rs
@@ -1238,7 +1238,11 @@ impl<'a> State<'a> {
                 if let Some((init, els)) = loc.kind.init_else_opt() {
                     self.nbsp();
                     self.word_space("=");
-                    self.print_expr(init, FixupContext::default());
+                    self.print_expr_cond_paren(
+                        init,
+                        els.is_some() && classify::expr_trailing_brace(init).is_some(),
+                        FixupContext::default(),
+                    );
                     if let Some(els) = els {
                         self.cbox(INDENT_UNIT);
                         self.ibox(INDENT_UNIT);
diff --git a/tests/ui/unpretty/let-else.stdout b/tests/ui/unpretty/let-else.stdout
index 5f6972cd4295f..4bc4d9e085f97 100644
--- a/tests/ui/unpretty/let-else.stdout
+++ b/tests/ui/unpretty/let-else.stdout
@@ -11,5 +11,5 @@ macro_rules! expr { ($e:expr) => { $e }; }
 
 fn main() {
     let _ = 1 + 1 else { return; };
-    let _ = loop {} else { return; };
+    let _ = (loop {}) else { return; };
 }