Update upstream source from tag 'upstream/1.52.1+dfsg1'

[rustc.git] / src / tools / clippy / clippy_lints / src / else_if_without_else.rs

diff --git a/src/tools/clippy/clippy_lints/src/else_if_without_else.rs b/src/tools/clippy/clippy_lints/src/else_if_without_else.rs
new file mode 100644 (file)
index 0000000..95123e6
--- /dev/null
+++ b/src/tools/clippy/clippy_lints/src/else_if_without_else.rs
@@ -0,0 +1,72 @@
+//! Lint on if expressions with an else if, but without a final else branch.
+
+use rustc_ast::ast::{Expr, ExprKind};
+use rustc_lint::{EarlyContext, EarlyLintPass, LintContext};
+use rustc_middle::lint::in_external_macro;
+use rustc_session::{declare_lint_pass, declare_tool_lint};
+
+use crate::utils::span_lint_and_help;
+
+declare_clippy_lint! {
+    /// **What it does:** Checks for usage of if expressions with an `else if` branch,
+    /// but without a final `else` branch.
+    ///
+    /// **Why is this bad?** Some coding guidelines require this (e.g., MISRA-C:2004 Rule 14.10).
+    ///
+    /// **Known problems:** None.
+    ///
+    /// **Example:**
+    /// ```rust
+    /// # fn a() {}
+    /// # fn b() {}
+    /// # let x: i32 = 1;
+    /// if x.is_positive() {
+    ///     a();
+    /// } else if x.is_negative() {
+    ///     b();
+    /// }
+    /// ```
+    ///
+    /// Could be written:
+    ///
+    /// ```rust
+    /// # fn a() {}
+    /// # fn b() {}
+    /// # let x: i32 = 1;
+    /// if x.is_positive() {
+    ///     a();
+    /// } else if x.is_negative() {
+    ///     b();
+    /// } else {
+    ///     // We don't care about zero.
+    /// }
+    /// ```
+    pub ELSE_IF_WITHOUT_ELSE,
+    restriction,
+    "`if` expression with an `else if`, but without a final `else` branch"
+}
+
+declare_lint_pass!(ElseIfWithoutElse => [ELSE_IF_WITHOUT_ELSE]);
+
+impl EarlyLintPass for ElseIfWithoutElse {
+    fn check_expr(&mut self, cx: &EarlyContext<'_>, mut item: &Expr) {
+        if in_external_macro(cx.sess(), item.span) {
+            return;
+        }
+
+        while let ExprKind::If(_, _, Some(ref els)) = item.kind {
+            if let ExprKind::If(_, _, None) = els.kind {
+                span_lint_and_help(
+                    cx,
+                    ELSE_IF_WITHOUT_ELSE,
+                    els.span,
+                    "`if` expression with an `else if`, but without a final `else`",
+                    None,
+                    "add an `else` block here",
+                );
+            }
+
+            item = els;
+        }
+    }
+}