From 282d313eb957149fdeeade03f218cc4478c91f62 Mon Sep 17 00:00:00 2001
From: Ahmed Karaman <20889958+ahmedkrmn@users.noreply.github.com>
Date: Fri, 29 Oct 2021 04:11:43 +0200
Subject: [PATCH] Disable "if_not_else" lints firing on else-ifs

1. Convert IfNotElse to LateLintPass and use
clippy_utils::is_else_clause for checking.
2. Update tests.
---
 clippy_lints/src/if_not_else.rs | 21 +++++++++++++++------
 clippy_lints/src/lib.rs         |  2 +-
 tests/ui/if_not_else.rs         | 10 ++++++++++
 tests/ui/if_not_else.stderr     |  4 ++--
 4 files changed, 28 insertions(+), 9 deletions(-)

diff --git a/clippy_lints/src/if_not_else.rs b/clippy_lints/src/if_not_else.rs
index 3ce91d421bac..d8c654284fc6 100644
--- a/clippy_lints/src/if_not_else.rs
+++ b/clippy_lints/src/if_not_else.rs
@@ -2,8 +2,9 @@
 //! on the condition
 
 use clippy_utils::diagnostics::span_lint_and_help;
-use rustc_ast::ast::{BinOpKind, Expr, ExprKind, UnOp};
-use rustc_lint::{EarlyContext, EarlyLintPass};
+use clippy_utils::is_else_clause;
+use rustc_hir::{BinOpKind, Expr, ExprKind, UnOp};
+use rustc_lint::{LateContext, LateLintPass, LintContext};
 use rustc_middle::lint::in_external_macro;
 use rustc_session::{declare_lint_pass, declare_tool_lint};
 
@@ -46,13 +47,21 @@ declare_clippy_lint! {
 
 declare_lint_pass!(IfNotElse => [IF_NOT_ELSE]);
 
-impl EarlyLintPass for IfNotElse {
-    fn check_expr(&mut self, cx: &EarlyContext<'_>, item: &Expr) {
-        if in_external_macro(cx.sess, item.span) {
+impl LateLintPass<'_> for IfNotElse {
+    fn check_expr(&mut self, cx: &LateContext<'_>, item: &Expr<'_>) {
+        if in_external_macro(cx.sess(), item.span) {
             return;
         }
-        if let ExprKind::If(ref cond, _, Some(ref els)) = item.kind {
+        if let ExprKind::If(mut cond, _, Some(els)) = item.kind {
             if let ExprKind::Block(..) = els.kind {
+                // Disable firing the lint in "else if" expressions.
+                if is_else_clause(cx.tcx, item) {
+                    return;
+                }
+
+                if let ExprKind::DropTemps(inner) = &cond.kind {
+                    cond = inner;
+                }
                 match cond.kind {
                     ExprKind::Unary(UnOp::Not, _) => {
                         span_lint_and_help(
diff --git a/clippy_lints/src/lib.rs b/clippy_lints/src/lib.rs
index fd5f164e7a1b..7174d0a082e0 100644
--- a/clippy_lints/src/lib.rs
+++ b/clippy_lints/src/lib.rs
@@ -668,7 +668,6 @@ pub fn register_plugins(store: &mut rustc_lint::LintStore, sess: &Session, conf:
     store.register_early_pass(|| Box::new(double_parens::DoubleParens));
     store.register_late_pass(|| Box::new(to_string_in_display::ToStringInDisplay::new()));
     store.register_early_pass(|| Box::new(unsafe_removed_from_name::UnsafeNameRemoval));
-    store.register_early_pass(|| Box::new(if_not_else::IfNotElse));
     store.register_early_pass(|| Box::new(else_if_without_else::ElseIfWithoutElse));
     store.register_early_pass(|| Box::new(int_plus_one::IntPlusOne));
     store.register_early_pass(|| Box::new(formatting::Formatting));
@@ -722,6 +721,7 @@ pub fn register_plugins(store: &mut rustc_lint::LintStore, sess: &Session, conf:
     store.register_late_pass(|| Box::new(option_if_let_else::OptionIfLetElse));
     store.register_late_pass(|| Box::new(future_not_send::FutureNotSend));
     store.register_late_pass(|| Box::new(if_let_mutex::IfLetMutex));
+    store.register_late_pass(|| Box::new(if_not_else::IfNotElse));
     store.register_late_pass(|| Box::new(equatable_if_let::PatternEquality));
     store.register_late_pass(|| Box::new(mut_mutex_lock::MutMutexLock));
     store.register_late_pass(|| Box::new(match_on_vec_items::MatchOnVecItems));
diff --git a/tests/ui/if_not_else.rs b/tests/ui/if_not_else.rs
index dc3fb1ceac9a..b7012b43d297 100644
--- a/tests/ui/if_not_else.rs
+++ b/tests/ui/if_not_else.rs
@@ -1,6 +1,9 @@
 #![warn(clippy::all)]
 #![warn(clippy::if_not_else)]
 
+fn foo() -> bool {
+    unimplemented!()
+}
 fn bla() -> bool {
     unimplemented!()
 }
@@ -16,4 +19,11 @@ fn main() {
     } else {
         println!("Bunny");
     }
+    if !foo() {
+        println!("Foo");
+    } else if !bla() {
+        println!("Bugs");
+    } else {
+        println!("Bunny");
+    }
 }
diff --git a/tests/ui/if_not_else.stderr b/tests/ui/if_not_else.stderr
index 53d1b86d02a9..8c8cc44bb035 100644
--- a/tests/ui/if_not_else.stderr
+++ b/tests/ui/if_not_else.stderr
@@ -1,5 +1,5 @@
 error: unnecessary boolean `not` operation
-  --> $DIR/if_not_else.rs:9:5
+  --> $DIR/if_not_else.rs:12:5
    |
 LL | /     if !bla() {
 LL | |         println!("Bugs");
@@ -12,7 +12,7 @@ LL | |     }
    = help: remove the `!` and swap the blocks of the `if`/`else`
 
 error: unnecessary `!=` operation
-  --> $DIR/if_not_else.rs:14:5
+  --> $DIR/if_not_else.rs:17:5
    |
 LL | /     if 4 != 5 {
 LL | |         println!("Bugs");