From e707447a861739fa3e12e9c05c039c8c9c6b0544 Mon Sep 17 00:00:00 2001
From: Pavan Kumar Sunkara <pavan.sss1991@gmail.com>
Date: Thu, 16 Feb 2023 11:32:12 +0000
Subject: [PATCH] Boilerplate for the new lint

---
 clippy_lints/src/methods/mod.rs               | 52 +++++++++++++++++++
 .../src/methods/unnecessary_literal_unwrap.rs | 30 +++++++++++
 tests/ui/unnecessary_literal_unwrap.rs        | 10 ++++
 tests/ui/unwrap_literal.rs                    | 17 ------
 4 files changed, 92 insertions(+), 17 deletions(-)
 create mode 100644 clippy_lints/src/methods/unnecessary_literal_unwrap.rs
 create mode 100644 tests/ui/unnecessary_literal_unwrap.rs
 delete mode 100644 tests/ui/unwrap_literal.rs

diff --git a/clippy_lints/src/methods/mod.rs b/clippy_lints/src/methods/mod.rs
index 88cbefbb5..f24f00ef6 100644
--- a/clippy_lints/src/methods/mod.rs
+++ b/clippy_lints/src/methods/mod.rs
@@ -93,6 +93,7 @@ mod unnecessary_fold;
 mod unnecessary_iter_cloned;
 mod unnecessary_join;
 mod unnecessary_lazy_eval;
+mod unnecessary_literal_unwrap;
 mod unnecessary_sort_by;
 mod unnecessary_to_owned;
 mod unwrap_or_else_default;
@@ -273,6 +274,56 @@ declare_clippy_lint! {
     "using `.unwrap()` on `Result` or `Option`, which should at least get a better message using `expect()`"
 }
 
+declare_clippy_lint! {
+    /// ### What it does
+    /// Checks for `.unwrap()` or `.unwrap_err()` calls on `Result`s and `.unwrap()` call on `Option`s.
+    ///
+    /// ### Why is this bad?
+    /// It is better to handle the `None` or `Err` case,
+    /// or at least call `.expect(_)` with a more helpful message. Still, for a lot of
+    /// quick-and-dirty code, `unwrap` is a good choice, which is why this lint is
+    /// `Allow` by default.
+    ///
+    /// `result.unwrap()` will let the thread panic on `Err` values.
+    /// Normally, you want to implement more sophisticated error handling,
+    /// and propagate errors upwards with `?` operator.
+    ///
+    /// Even if you want to panic on errors, not all `Error`s implement good
+    /// messages on display. Therefore, it may be beneficial to look at the places
+    /// where they may get displayed. Activate this lint to do just that.
+    ///
+    /// ### Examples
+    /// ```rust
+    /// # let option = Some(1);
+    /// # let result: Result<usize, ()> = Ok(1);
+    /// option.unwrap();
+    /// result.unwrap();
+    /// ```
+    ///
+    /// Use instead:
+    /// ```rust
+    /// # let option = Some(1);
+    /// # let result: Result<usize, ()> = Ok(1);
+    /// option.expect("more helpful message");
+    /// result.expect("more helpful message");
+    /// ```
+    ///
+    /// If [expect_used](#expect_used) is enabled, instead:
+    /// ```rust,ignore
+    /// # let option = Some(1);
+    /// # let result: Result<usize, ()> = Ok(1);
+    /// option?;
+    ///
+    /// // or
+    ///
+    /// result?;
+    /// ```
+    #[clippy::version = "1.69.0"]
+    pub UNNECESSARY_LITERAL_UNWRAP,
+    complexity,
+    "checks for calls of `unwrap()` or `expect()` on `Some()` that cannot fail"
+}
+
 declare_clippy_lint! {
     /// ### What it does
     /// Checks for `.expect()` or `.expect_err()` calls on `Result`s and `.expect()` call on `Option`s.
@@ -3814,6 +3865,7 @@ impl Methods {
                         Some(("or", recv, [or_arg], or_span, _)) => {
                             or_then_unwrap::check(cx, expr, recv, or_arg, or_span);
                         },
+                        // unnecessary_literal_unwrap::check(cx, expr, recv);
                         _ => {},
                     }
                     unwrap_used::check(cx, expr, recv, false, self.allow_unwrap_in_tests);
diff --git a/clippy_lints/src/methods/unnecessary_literal_unwrap.rs b/clippy_lints/src/methods/unnecessary_literal_unwrap.rs
new file mode 100644
index 000000000..39b30b776
--- /dev/null
+++ b/clippy_lints/src/methods/unnecessary_literal_unwrap.rs
@@ -0,0 +1,30 @@
+use clippy_utils::diagnostics::span_lint_and_help;
+use clippy_utils::ty::is_type_diagnostic_item;
+use rustc_hir as hir;
+use rustc_lint::LateContext;
+use rustc_span::sym;
+
+use super::UNNECESSARY_LITERAL_UNWRAP;
+
+pub(super) fn check(cx: &LateContext<'_>, expr: &hir::Expr<'_>, recv: &hir::Expr<'_>) {
+    let obj_ty = cx.typeck_results().expr_ty(recv).peel_refs();
+
+    let mess = if is_type_diagnostic_item(cx, obj_ty, sym::Option) {
+        Some((UNNECESSARY_LITERAL_UNWRAP, "an `Option`", "None", ""))
+    } else {
+        None
+    };
+
+    if let Some((lint, kind, none_value, none_prefix)) = mess {
+        let help = format!("if this value is {none_prefix}`{none_value}`, it will panic");
+
+        span_lint_and_help(
+            cx,
+            lint,
+            expr.span,
+            &format!("used `unwrap()` on {kind} value"),
+            None,
+            &help,
+        );
+    }
+}
diff --git a/tests/ui/unnecessary_literal_unwrap.rs b/tests/ui/unnecessary_literal_unwrap.rs
new file mode 100644
index 000000000..9ae50517a
--- /dev/null
+++ b/tests/ui/unnecessary_literal_unwrap.rs
@@ -0,0 +1,10 @@
+#![warn(clippy::unnecessary_literal_unwrap)]
+
+fn unwrap_option() {
+    let val = Some(1).unwrap();
+    let val = Some(1).expect("this never happens");
+}
+
+fn main() {
+    unwrap_option();
+}
diff --git a/tests/ui/unwrap_literal.rs b/tests/ui/unwrap_literal.rs
deleted file mode 100644
index 917ef2126..000000000
--- a/tests/ui/unwrap_literal.rs
+++ /dev/null
@@ -1,17 +0,0 @@
-#![warn(clippy::unnecessary_unwrap)]
-
-fn unwrap_option() {
-    let val = Some(1).unwrap();
-    let val = Some(1).expect("this never happens");
-}
-
-fn unwrap_result() {
-    let val = Ok(1).unwrap();
-    let val = Err(1).unwrap_err();
-    let val = Ok(1).expect("this never happens");
-}
-
-fn main() {
-    unwrap_option();
-    unwrap_result();
-}