Extend unnecessary_unwrap to look for expect in addition to unwrap

Closes #7581

Author: shepmaster

clippy_lints/src/unwrap.rs

@@ -172,8 +172,8 @@ impl<'a, 'tcx> Visitor<'tcx> for UnwrappableVariablesVisitor<'a, 'tcx> {
             if_chain! {
                 if let ExprKind::MethodCall(method_name, _, args, _) = expr.kind;
                 if let ExprKind::Path(QPath::Resolved(None, path)) = args[0].kind;
-                if [sym::unwrap, sym!(unwrap_err)].contains(&method_name.ident.name);
-                let call_to_unwrap = method_name.ident.name == sym::unwrap;
+                if [sym::unwrap, sym::expect, sym!(unwrap_err)].contains(&method_name.ident.name);
+                let call_to_unwrap = [sym::unwrap, sym::expect].contains(&method_name.ident.name);
                 if let Some(unwrappable) = self.unwrappables.iter()
                     .find(|u| u.ident.res == path.res);
                 // Span contexts should not differ with the conditional branch

tests/ui/checked_unwrap/simple_conditionals.rs

@@ -37,8 +37,10 @@ fn main() {
     let x = Some(());
     if x.is_some() {
         x.unwrap(); // unnecessary
+        x.expect("an error message"); // unnecessary
     } else {
         x.unwrap(); // will panic
+        x.expect("an error message"); // will panic
     }
     if x.is_none() {
         x.unwrap(); // will panic
@@ -52,9 +54,11 @@ fn main() {
     let mut x: Result<(), ()> = Ok(());
     if x.is_ok() {
         x.unwrap(); // unnecessary
+        x.expect("an error message"); // unnecessary
         x.unwrap_err(); // will panic
     } else {
         x.unwrap(); // will panic
+        x.expect("an error message"); // will panic
         x.unwrap_err(); // unnecessary
     }
     if x.is_err() {

tests/ui/checked_unwrap/simple_conditionals.stderr

@@ -12,8 +12,17 @@ note: the lint level is defined here
 LL | #![deny(clippy::panicking_unwrap, clippy::unnecessary_unwrap)]
    |                                   ^^^^^^^^^^^^^^^^^^^^^^^^^^
 
+error: you checked before that `expect()` cannot fail, instead of checking and unwrapping, it's better to use `if let` or `match`
+  --> $DIR/simple_conditionals.rs:40:9
+   |
+LL |     if x.is_some() {
+   |        ----------- the check is happening here
+LL |         x.unwrap(); // unnecessary
+LL |         x.expect("an error message"); // unnecessary
+   |         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
 error: this call to `unwrap()` will always panic
-  --> $DIR/simple_conditionals.rs:41:9
+  --> $DIR/simple_conditionals.rs:42:9
    |
 LL |     if x.is_some() {
    |        ----------- because of this check
@@ -27,16 +36,25 @@ note: the lint level is defined here
 LL | #![deny(clippy::panicking_unwrap, clippy::unnecessary_unwrap)]
    |         ^^^^^^^^^^^^^^^^^^^^^^^^
 
+error: this call to `expect()` will always panic
+  --> $DIR/simple_conditionals.rs:43:9
+   |
+LL |     if x.is_some() {
+   |        ----------- because of this check
+...
+LL |         x.expect("an error message"); // will panic
+   |         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
 error: this call to `unwrap()` will always panic
-  --> $DIR/simple_conditionals.rs:44:9
+  --> $DIR/simple_conditionals.rs:46:9
    |
 LL |     if x.is_none() {
    |        ----------- because of this check
 LL |         x.unwrap(); // will panic
    |         ^^^^^^^^^^
 
 error: you checked before that `unwrap()` cannot fail, instead of checking and unwrapping, it's better to use `if let` or `match`
-  --> $DIR/simple_conditionals.rs:46:9
+  --> $DIR/simple_conditionals.rs:48:9
    |
 LL |     if x.is_none() {
    |        ----------- the check is happening here
@@ -58,33 +76,51 @@ LL |     m!(x);
    = note: this error originates in the macro `m` (in Nightly builds, run with -Z macro-backtrace for more info)
 
 error: you checked before that `unwrap()` cannot fail, instead of checking and unwrapping, it's better to use `if let` or `match`
-  --> $DIR/simple_conditionals.rs:54:9
+  --> $DIR/simple_conditionals.rs:56:9
    |
 LL |     if x.is_ok() {
    |        --------- the check is happening here
 LL |         x.unwrap(); // unnecessary
    |         ^^^^^^^^^^
 
+error: you checked before that `expect()` cannot fail, instead of checking and unwrapping, it's better to use `if let` or `match`
+  --> $DIR/simple_conditionals.rs:57:9
+   |
+LL |     if x.is_ok() {
+   |        --------- the check is happening here
+LL |         x.unwrap(); // unnecessary
+LL |         x.expect("an error message"); // unnecessary
+   |         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
 error: this call to `unwrap_err()` will always panic
-  --> $DIR/simple_conditionals.rs:55:9
+  --> $DIR/simple_conditionals.rs:58:9
    |
 LL |     if x.is_ok() {
    |        --------- because of this check
-LL |         x.unwrap(); // unnecessary
+...
 LL |         x.unwrap_err(); // will panic
    |         ^^^^^^^^^^^^^^
 
 error: this call to `unwrap()` will always panic
-  --> $DIR/simple_conditionals.rs:57:9
+  --> $DIR/simple_conditionals.rs:60:9
    |
 LL |     if x.is_ok() {
    |        --------- because of this check
 ...
 LL |         x.unwrap(); // will panic
    |         ^^^^^^^^^^
 
+error: this call to `expect()` will always panic
+  --> $DIR/simple_conditionals.rs:61:9
+   |
+LL |     if x.is_ok() {
+   |        --------- because of this check
+...
+LL |         x.expect("an error message"); // will panic
+   |         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
 error: you checked before that `unwrap_err()` cannot fail, instead of checking and unwrapping, it's better to use `if let` or `match`
-  --> $DIR/simple_conditionals.rs:58:9
+  --> $DIR/simple_conditionals.rs:62:9
    |
 LL |     if x.is_ok() {
    |        --------- the check is happening here
@@ -93,15 +129,15 @@ LL |         x.unwrap_err(); // unnecessary
    |         ^^^^^^^^^^^^^^
 
 error: this call to `unwrap()` will always panic
-  --> $DIR/simple_conditionals.rs:61:9
+  --> $DIR/simple_conditionals.rs:65:9
    |
 LL |     if x.is_err() {
    |        ---------- because of this check
 LL |         x.unwrap(); // will panic
    |         ^^^^^^^^^^
 
 error: you checked before that `unwrap_err()` cannot fail, instead of checking and unwrapping, it's better to use `if let` or `match`
-  --> $DIR/simple_conditionals.rs:62:9
+  --> $DIR/simple_conditionals.rs:66:9
    |
 LL |     if x.is_err() {
    |        ---------- the check is happening here
@@ -110,7 +146,7 @@ LL |         x.unwrap_err(); // unnecessary
    |         ^^^^^^^^^^^^^^
 
 error: you checked before that `unwrap()` cannot fail, instead of checking and unwrapping, it's better to use `if let` or `match`
-  --> $DIR/simple_conditionals.rs:64:9
+  --> $DIR/simple_conditionals.rs:68:9
    |
 LL |     if x.is_err() {
    |        ---------- the check is happening here
@@ -119,13 +155,13 @@ LL |         x.unwrap(); // unnecessary
    |         ^^^^^^^^^^
 
 error: this call to `unwrap_err()` will always panic
-  --> $DIR/simple_conditionals.rs:65:9
+  --> $DIR/simple_conditionals.rs:69:9
    |
 LL |     if x.is_err() {
    |        ---------- because of this check
 ...
 LL |         x.unwrap_err(); // will panic
    |         ^^^^^^^^^^^^^^
 
-error: aborting due to 13 previous errors
+error: aborting due to 17 previous errors