Fix unnecessary_unwrap false negative (#12295) (#15689)

Fix `unnecessary_unwrap` false negative when unwrapping a known value
inside a macro call

Fixes #12295
Produces no changes to `lintcheck`

changelog: [`unnecessary_unwrap`]: Fix false negative when unwrapping a
known value inside a macro call

I made sue to run `cargo dev fmt`.
I also ran the following checks (in order) on a fresh clone of mi fork:
1. `cargo build`
2. `cargo test`
3. `cargo lintcheck`

Running `cargo test` after `lintcheck` causes a test to fail, but this
also happens on a clean fork without my changes

Author: Alexendoo

clippy_lints/src/unwrap.rs

@@ -292,6 +292,7 @@ impl<'tcx> Visitor<'tcx> for UnwrappableVariablesVisitor<'_, 'tcx> {
     fn visit_expr(&mut self, expr: &'tcx Expr<'_>) {
         // Shouldn't lint when `expr` is in macro.
         if expr.span.in_external_macro(self.cx.tcx.sess.source_map()) {
+            walk_expr(self, expr);
             return;
         }
         // Skip checking inside closures since they are visited through `Unwrap::check_fn()` already.

tests/ui/checked_unwrap/simple_conditionals.rs

@@ -273,6 +273,28 @@ const ISSUE14763: fn(Option<String>) = |x| {
     }
 };
 
+fn issue12295() {
+    let option = Some(());
+
+    if option.is_some() {
+        println!("{:?}", option.unwrap());
+        //~^ unnecessary_unwrap
+    } else {
+        println!("{:?}", option.unwrap());
+        //~^ panicking_unwrap
+    }
+
+    let result = Ok::<(), ()>(());
+
+    if result.is_ok() {
+        println!("{:?}", result.unwrap());
+        //~^ unnecessary_unwrap
+    } else {
+        println!("{:?}", result.unwrap());
+        //~^ panicking_unwrap
+    }
+}
+
 fn check_expect() {
     let x = Some(());
     if x.is_some() {

tests/ui/checked_unwrap/simple_conditionals.stderr

@@ -322,6 +322,40 @@ LL |         if x.is_some() {
 LL |             _ = x.unwrap();
    |                 ^^^^^^^^^^
 
+error: called `unwrap` on `option` after checking its variant with `is_some`
+  --> tests/ui/checked_unwrap/simple_conditionals.rs:280:26
+   |
+LL |     if option.is_some() {
+   |     ------------------- help: try: `if let Some(<item>) = option`
+LL |         println!("{:?}", option.unwrap());
+   |                          ^^^^^^^^^^^^^^^
+
+error: this call to `unwrap()` will always panic
+  --> tests/ui/checked_unwrap/simple_conditionals.rs:283:26
+   |
+LL |     if option.is_some() {
+   |        ---------------- because of this check
+...
+LL |         println!("{:?}", option.unwrap());
+   |                          ^^^^^^^^^^^^^^^
+
+error: called `unwrap` on `result` after checking its variant with `is_ok`
+  --> tests/ui/checked_unwrap/simple_conditionals.rs:290:26
+   |
+LL |     if result.is_ok() {
+   |     ----------------- help: try: `if let Ok(<item>) = result`
+LL |         println!("{:?}", result.unwrap());
+   |                          ^^^^^^^^^^^^^^^
+
+error: this call to `unwrap()` will always panic
+  --> tests/ui/checked_unwrap/simple_conditionals.rs:293:26
+   |
+LL |     if result.is_ok() {
+   |        -------------- because of this check
+...
+LL |         println!("{:?}", result.unwrap());
+   |                          ^^^^^^^^^^^^^^^
+
 error: creating a shared reference to mutable static
   --> tests/ui/checked_unwrap/simple_conditionals.rs:183:12
    |
@@ -332,5 +366,5 @@ LL |         if X.is_some() {
    = note: shared references to mutable statics are dangerous; it's undefined behavior if the static is mutated or if a mutable reference is created for it while the shared reference lives
    = note: `#[deny(static_mut_refs)]` (part of `#[deny(rust_2024_compatibility)]`) on by default
 
-error: aborting due to 36 previous errors
+error: aborting due to 40 previous errors