Revert let_chains stabilization

[rust.git] / clippy_lints / src / if_not_else.rs

diff --git a/clippy_lints/src/if_not_else.rs b/clippy_lints/src/if_not_else.rs
index 385ba9f16c89ee63d841689270434c51b717fee4..3d59b783337a441b3ca1151f19667fe0174b41b4 100644 (file)
--- a/clippy_lints/src/if_not_else.rs
+++ b/clippy_lints/src/if_not_else.rs
@@ -1,22 +1,25 @@
 //! lint on if branches that could be swapped so no `!` operation is necessary
 //! on the condition
 
-use rustc::lint::{in_external_macro, EarlyContext, EarlyLintPass, LintArray, LintContext, LintPass};
-use rustc::{declare_lint_pass, declare_tool_lint};
-use syntax::ast::*;
-
-use crate::utils::span_help_and_lint;
+use clippy_utils::diagnostics::span_lint_and_help;
+use clippy_utils::is_else_clause;
+use rustc_hir::{BinOpKind, Expr, ExprKind, UnOp};
+use rustc_lint::{LateContext, LateLintPass};
+use rustc_session::{declare_lint_pass, declare_tool_lint};
 
 declare_clippy_lint! {
-    /// **What it does:** Checks for usage of `!` or `!=` in an if condition with an
+    /// ### What it does
+    /// Checks for usage of `!` or `!=` in an if condition with an
     /// else branch.
     ///
-    /// **Why is this bad?** Negations reduce the readability of statements.
-    ///
-    /// **Known problems:** None.
+    /// ### Why is this bad?
+    /// Negations reduce the readability of statements.
     ///
-    /// **Example:**
+    /// ### Example
     /// ```rust
+    /// # let v: Vec<usize> = vec![];
+    /// # fn a() {}
+    /// # fn b() {}
     /// if !v.is_empty() {
     ///     a()
     /// } else {
@@ -27,12 +30,16 @@
     /// Could be written:
     ///
     /// ```rust
+    /// # let v: Vec<usize> = vec![];
+    /// # fn a() {}
+    /// # fn b() {}
     /// if v.is_empty() {
     ///     b()
     /// } else {
     ///     a()
     /// }
     /// ```
+    #[clippy::version = "pre 1.29.0"]
     pub IF_NOT_ELSE,
     pedantic,
     "`if` branches that could be swapped so no negation operation is necessary on the condition"
@@ -40,30 +47,39 @@
 
 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<'_>) {
+        // While loops will be desugared to ExprKind::If. This will cause the lint to fire.
+        // To fix this, return early if this span comes from a macro or desugaring.
+        if item.span.from_expansion() {
             return;
         }
-        if let ExprKind::If(ref cond, _, Some(ref els)) = item.node {
-            if let ExprKind::Block(..) = els.node {
-                match cond.node {
+        if let ExprKind::If(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;
+                }
+
+                match cond.peel_drop_temps().kind {
                     ExprKind::Unary(UnOp::Not, _) => {
-                        span_help_and_lint(
+                        span_lint_and_help(
                             cx,
                             IF_NOT_ELSE,
                             item.span,
-                            "Unnecessary boolean `not` operation",
-                            "remove the `!` and swap the blocks of the if/else",
+                            "unnecessary boolean `not` operation",
+                            None,
+                            "remove the `!` and swap the blocks of the `if`/`else`",
                         );
                     },
                     ExprKind::Binary(ref kind, _, _) if kind.node == BinOpKind::Ne => {
-                        span_help_and_lint(
+                        span_lint_and_help(
                             cx,
                             IF_NOT_ELSE,
                             item.span,
-                            "Unnecessary `!=` operation",
-                            "change to `==` and swap the blocks of the if/else",
+                            "unnecessary `!=` operation",
+                            None,
+                            "change to `==` and swap the blocks of the `if`/`else`",
                         );
                     },
                     _ => (),