Unwrap DropTemps in higher::if_block

Author: Manishearth

clippy_lints/src/utils/higher.rs

@@ -203,6 +203,11 @@ pub fn for_loop(expr: &hir::Expr) -> Option<(&hir::Pat, &hir::Expr, &hir::Expr)>
 /// `if cond { then } else { els }` becomes `(cond, then, Some(els))`
 pub fn if_block(expr: &hir::Expr) -> Option<(&hir::Expr, &hir::Expr, Option<&hir::Expr>)> {
     if let hir::ExprKind::Match(ref cond, ref arms, hir::MatchSource::IfDesugar {..}) = expr.node {
+        let cond = if let hir::ExprKind::DropTemps(ref cond) = cond.node {
+            cond
+        } else {
+            panic!("If block desugar must contain DropTemps");
+        };
         let then = &arms[0].body;
         let els = arms.get(1).map(|x| &*x.body);
         Some((cond, then, els))