From af19ff8cc89bb6a010faaf110eb63e1fbce49b1a Mon Sep 17 00:00:00 2001
From: Folkert de Vries <folkert@folkertdev.nl>
Date: Thu, 17 Jul 2025 19:16:39 +0200
Subject: [PATCH] fix `collapsable_if` when the inner `if` is in parens

---
 clippy_lints/src/collapsible_if.rs | 51 +++++++++++++++++++++++++++++-
 tests/ui/collapsible_if.fixed      |  8 +++++
 tests/ui/collapsible_if.rs         |  9 ++++++
 tests/ui/collapsible_if.stderr     | 20 +++++++++++-
 4 files changed, 86 insertions(+), 2 deletions(-)

diff --git a/clippy_lints/src/collapsible_if.rs b/clippy_lints/src/collapsible_if.rs
index 1854d86c53b2..da0f0b2f1be9 100644
--- a/clippy_lints/src/collapsible_if.rs
+++ b/clippy_lints/src/collapsible_if.rs
@@ -187,7 +187,8 @@ impl CollapsibleIf {
                             .with_leading_whitespace(cx)
                             .into_span()
                     };
-                    let inner_if = inner.span.split_at(2).0;
+                    let (paren_start, inner_if_span, paren_end) = peel_parens(cx.tcx.sess.source_map(), inner.span);
+                    let inner_if = inner_if_span.split_at(2).0;
                     let mut sugg = vec![
                         // Remove the outer then block `{`
                         (then_open_bracket, String::new()),
@@ -196,6 +197,17 @@ impl CollapsibleIf {
                         // Replace inner `if` by `&&`
                         (inner_if, String::from("&&")),
                     ];
+
+                    if !paren_start.is_empty() {
+                        // Remove any leading parentheses '('
+                        sugg.push((paren_start, String::new()));
+                    }
+
+                    if !paren_end.is_empty() {
+                        // Remove any trailing parentheses ')'
+                        sugg.push((paren_end, String::new()));
+                    }
+
                     sugg.extend(parens_around(check));
                     sugg.extend(parens_around(check_inner));
 
@@ -285,3 +297,40 @@ fn span_extract_keyword(sm: &SourceMap, span: Span, keyword: &str) -> Option<Spa
         })
         .next()
 }
+
+fn peel_parens(sm: &SourceMap, mut span: Span) -> (Span, Span, Span) {
+    use crate::rustc_span::Pos;
+    use rustc_span::SpanData;
+
+    let start = span.shrink_to_lo();
+    let end = span.shrink_to_hi();
+
+    loop {
+        let data = span.data();
+        let snippet = sm.span_to_snippet(span).unwrap();
+
+        let trim_start = snippet.len() - snippet.trim_start().len();
+        let trim_end = snippet.len() - snippet.trim_end().len();
+
+        let trimmed = snippet.trim();
+
+        if trimmed.starts_with('(') && trimmed.ends_with(')') {
+            // Try to remove one layer of parens by adjusting the span
+            span = SpanData {
+                lo: data.lo + BytePos::from_usize(trim_start + 1),
+                hi: data.hi - BytePos::from_usize(trim_end + 1),
+                ctxt: data.ctxt,
+                parent: data.parent,
+            }
+            .span();
+
+            continue;
+        }
+
+        break;
+    }
+
+    (start.with_hi(span.lo()),
+    span,
+    end.with_lo(span.hi()))
+}
diff --git a/tests/ui/collapsible_if.fixed b/tests/ui/collapsible_if.fixed
index 77bc791ea8e9..f7c840c4cc1e 100644
--- a/tests/ui/collapsible_if.fixed
+++ b/tests/ui/collapsible_if.fixed
@@ -163,3 +163,11 @@ fn issue14799() {
         if true {}
     };
 }
+
+fn in_parens() {
+    if true
+        && true {
+            println!("In parens, linted");
+        }
+    //~^^^^^ collapsible_if
+}
diff --git a/tests/ui/collapsible_if.rs b/tests/ui/collapsible_if.rs
index d30df157d5eb..4faebcb0ca0d 100644
--- a/tests/ui/collapsible_if.rs
+++ b/tests/ui/collapsible_if.rs
@@ -173,3 +173,12 @@ fn issue14799() {
         if true {}
     };
 }
+
+fn in_parens() {
+    if true {
+        (if true {
+            println!("In parens, linted");
+        })
+    }
+    //~^^^^^ collapsible_if
+}
diff --git a/tests/ui/collapsible_if.stderr b/tests/ui/collapsible_if.stderr
index 32c6b0194030..a685cc2e9291 100644
--- a/tests/ui/collapsible_if.stderr
+++ b/tests/ui/collapsible_if.stderr
@@ -190,5 +190,23 @@ LL |         // This is a comment, do not collapse code to it
 LL ~     ; 3
    |
 
-error: aborting due to 11 previous errors
+error: this `if` statement can be collapsed
+  --> tests/ui/collapsible_if.rs:178:5
+   |
+LL | /     if true {
+LL | |         (if true {
+LL | |             println!("In parens, linted");
+LL | |         })
+LL | |     }
+   | |_____^
+   |
+help: collapse nested if block
+   |
+LL ~     if true
+LL ~         && true {
+LL |             println!("In parens, linted");
+LL ~         }
+   |
+
+error: aborting due to 12 previous errors