fix: collapsible_else_if FP on conditionally compiled stmt

Author: profetia

clippy_lints/src/collapsible_if.rs

@@ -1,10 +1,14 @@
 use clippy_config::Conf;
 use clippy_utils::diagnostics::{span_lint_and_sugg, span_lint_and_then};
 use clippy_utils::msrvs::{self, Msrv};
-use clippy_utils::source::{IntoSpan as _, SpanRangeExt, snippet, snippet_block, snippet_block_with_applicability};
+use clippy_utils::source::{
+    IntoSpan as _, SpanRangeExt, snippet, snippet_block, snippet_block_with_applicability, snippet_opt,
+};
+use clippy_utils::tokenize_with_text;
 use rustc_ast::BinOpKind;
 use rustc_errors::Applicability;
 use rustc_hir::{Block, Expr, ExprKind, Stmt, StmtKind};
+use rustc_lexer::TokenKind;
 use rustc_lint::{LateContext, LateLintPass};
 use rustc_session::impl_lint_pass;
 use rustc_span::Span;
@@ -96,6 +100,8 @@ impl CollapsibleIf {
             && cx.tcx.hir_attrs(else_.hir_id).is_empty()
             && !else_.span.from_expansion()
             && let ExprKind::If(..) = else_.kind
+            && let up_to_if = else_block.span.until(else_.span)
+            && span_not_contain_stmt(cx, up_to_if)
         {
             // Prevent "elseif"
             // Check that the "else" is followed by whitespace
@@ -198,6 +204,12 @@ fn block_starts_with_comment(cx: &LateContext<'_>, block: &Block<'_>) -> bool {
     trimmed_block_text.starts_with("//") || trimmed_block_text.starts_with("/*")
 }
 
+fn span_not_contain_stmt(cx: &LateContext<'_>, span: Span) -> bool {
+    matches!(snippet_opt(cx, span), Some(text) if tokenize_with_text(&text[1..]).all(|(token, _, _)| {
+        matches!(token, TokenKind::LineComment { .. } | TokenKind::BlockComment { .. } | TokenKind::Whitespace)
+    }))
+}
+
 /// If `block` is a block with either one expression or a statement containing an expression,
 /// return the expression. We don't peel blocks recursively, as extra blocks might be intentional.
 fn expr_block<'tcx>(block: &Block<'tcx>) -> Option<&'tcx Expr<'tcx>> {

tests/ui/collapsible_else_if.fixed

@@ -86,3 +86,21 @@ fn issue_7318() {
     }else if false {}
     //~^^^ collapsible_else_if
 }
+
+fn issue14799() {
+    use std::ops::ControlFlow;
+
+    let c: ControlFlow<_, ()> = ControlFlow::Break(Some(42));
+    if let ControlFlow::Break(Some(_)) = c {
+        todo!();
+    } else {
+        #[cfg(target_os = "freebsd")]
+        todo!();
+
+        if let ControlFlow::Break(None) = c {
+            todo!();
+        } else {
+            todo!();
+        }
+    }
+}

tests/ui/collapsible_else_if.rs

@@ -102,3 +102,21 @@ fn issue_7318() {
     }
     //~^^^ collapsible_else_if
 }
+
+fn issue14799() {
+    use std::ops::ControlFlow;
+
+    let c: ControlFlow<_, ()> = ControlFlow::Break(Some(42));
+    if let ControlFlow::Break(Some(_)) = c {
+        todo!();
+    } else {
+        #[cfg(target_os = "freebsd")]
+        todo!();
+
+        if let ControlFlow::Break(None) = c {
+            todo!();
+        } else {
+            todo!();
+        }
+    }
+}