From c54301f114d6fab44e8305da328eece26f682456 Mon Sep 17 00:00:00 2001
From: cardigan1008 <211250058@smail.nju.edu.cn>
Date: Thu, 9 May 2024 14:36:54 +0800
Subject: [PATCH 1/3] fix: Add if to check whether the previous node is Block

---
 compiler/rustc_middle/src/hir/map/mod.rs | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/compiler/rustc_middle/src/hir/map/mod.rs b/compiler/rustc_middle/src/hir/map/mod.rs
index c7aea137b6841..0deafb73d0ed9 100644
--- a/compiler/rustc_middle/src/hir/map/mod.rs
+++ b/compiler/rustc_middle/src/hir/map/mod.rs
@@ -563,6 +563,9 @@ impl<'hir> Map<'hir> {
                     // We verify that indirectly by checking that the previous node is the
                     // current node's body
                     if node.body_id().map(|b| b.hir_id) == prev_hir_id =>  {
+                        if let Node::Expr(Expr { kind: ExprKind::Block(_, _), ..}) = self.tcx.hir_node(prev_hir_id.unwrap()) {
+                            return None;
+                        }
                         return Some(hir_id)
                 }
                 // Ignore `return`s on the first iteration

From 62318b38ef591c70d9db875e88a04aa37c565828 Mon Sep 17 00:00:00 2001
From: cardigan1008 <211250058@smail.nju.edu.cn>
Date: Thu, 9 May 2024 23:44:54 +0800
Subject: [PATCH 2/3] fix: Check whether next_node is else-less if in
 get_return_block

Fix #124819, where a if-less block causes a wrong output. It is
caused by get_return_block in get_fn_decl. In get_return_block,
when a else-less if expression is the tail expression, the check
for next_node will keep iterating. So it is necessary to make a
early return in the check.
---
 compiler/rustc_middle/src/hir/map/mod.rs | 4 +---
 1 file changed, 1 insertion(+), 3 deletions(-)

diff --git a/compiler/rustc_middle/src/hir/map/mod.rs b/compiler/rustc_middle/src/hir/map/mod.rs
index 0deafb73d0ed9..f4ecc0973ef29 100644
--- a/compiler/rustc_middle/src/hir/map/mod.rs
+++ b/compiler/rustc_middle/src/hir/map/mod.rs
@@ -549,6 +549,7 @@ impl<'hir> Map<'hir> {
                     Node::Block(Block { expr: None, .. }) => return None,
                     // The current node is not the tail expression of its parent.
                     Node::Block(Block { expr: Some(e), .. }) if hir_id != e.hir_id => return None,
+                    Node::Block(Block { expr: Some(e), ..}) if matches!(e.kind, ExprKind::If(_, _, None)) => return None,
                     _ => {}
                 }
             }
@@ -563,9 +564,6 @@ impl<'hir> Map<'hir> {
                     // We verify that indirectly by checking that the previous node is the
                     // current node's body
                     if node.body_id().map(|b| b.hir_id) == prev_hir_id =>  {
-                        if let Node::Expr(Expr { kind: ExprKind::Block(_, _), ..}) = self.tcx.hir_node(prev_hir_id.unwrap()) {
-                            return None;
-                        }
                         return Some(hir_id)
                 }
                 // Ignore `return`s on the first iteration

From c811acb1f36cdeb45b46c490b7a308851347dc0d Mon Sep 17 00:00:00 2001
From: cardigan1008 <211250058@smail.nju.edu.cn>
Date: Thu, 16 May 2024 21:10:07 +0800
Subject: [PATCH 3/3] feat: add unit test

---
 tests/ui/return/tail-expr-if-as-return.rs     |  5 +++++
 tests/ui/return/tail-expr-if-as-return.stderr | 12 ++++++++++++
 2 files changed, 17 insertions(+)
 create mode 100644 tests/ui/return/tail-expr-if-as-return.rs
 create mode 100644 tests/ui/return/tail-expr-if-as-return.stderr

diff --git a/tests/ui/return/tail-expr-if-as-return.rs b/tests/ui/return/tail-expr-if-as-return.rs
new file mode 100644
index 0000000000000..119ffccc6a945
--- /dev/null
+++ b/tests/ui/return/tail-expr-if-as-return.rs
@@ -0,0 +1,5 @@
+fn main() {
+    if true {
+        "" //~ ERROR mismatched types [E0308]
+    }
+}
diff --git a/tests/ui/return/tail-expr-if-as-return.stderr b/tests/ui/return/tail-expr-if-as-return.stderr
new file mode 100644
index 0000000000000..2631f1e426ded
--- /dev/null
+++ b/tests/ui/return/tail-expr-if-as-return.stderr
@@ -0,0 +1,12 @@
+error[E0308]: mismatched types
+  --> $DIR/tail-expr-if-as-return.rs:3:9
+   |
+LL | /     if true {
+LL | |         ""
+   | |         ^^ expected `()`, found `&str`
+LL | |     }
+   | |_____- expected this to be `()`
+
+error: aborting due to 1 previous error
+
+For more information about this error, try `rustc --explain E0308`.