do not apply [assertions_on_result_states] to unwrap unit type

Signed-off-by: tabokie <[email protected]>

Author: tabokie

clippy_lints/src/assertions_on_result_states.rs

@@ -53,13 +53,14 @@ impl<'tcx> LateLintPass<'tcx> for AssertionsOnResultStates {
                 if result_type_with_refs != result_type {
                     return;
                 } else if let Res::Local(binding_id) = path_res(cx, recv)
-                    && local_used_after_expr(cx, binding_id, recv) {
+                    && local_used_after_expr(cx, binding_id, recv)
+                {
                     return;
                 }
             }
             let mut app = Applicability::MachineApplicable;
             match method_segment.ident.as_str() {
-                "is_ok" if has_debug_impl(cx, substs.type_at(1)) => {
+                "is_ok" if type_suitable_to_unwrap(cx, substs.type_at(1)) => {
                     span_lint_and_sugg(
                         cx,
                         ASSERTIONS_ON_RESULT_STATES,
@@ -73,7 +74,7 @@ impl<'tcx> LateLintPass<'tcx> for AssertionsOnResultStates {
                         app,
                     );
                 }
-                "is_err" if has_debug_impl(cx, substs.type_at(0)) => {
+                "is_err" if type_suitable_to_unwrap(cx, substs.type_at(0)) => {
                     span_lint_and_sugg(
                         cx,
                         ASSERTIONS_ON_RESULT_STATES,
@@ -99,3 +100,7 @@ fn has_debug_impl<'tcx>(cx: &LateContext<'tcx>, ty: Ty<'tcx>) -> bool {
         .get_diagnostic_item(sym::Debug)
         .map_or(false, |debug| implements_trait(cx, ty, debug, &[]))
 }
+
+fn type_suitable_to_unwrap<'tcx>(cx: &LateContext<'tcx>, ty: Ty<'tcx>) -> bool {
+    has_debug_impl(cx, ty) && !ty.is_unit() && !ty.is_never()
+}

tests/ui/assertions_on_result_states.fixed

@@ -27,6 +27,14 @@ fn main() {
     let r: Result<Foo, Foo> = Ok(Foo);
     assert!(r.is_ok());
 
+    // test ok with some messages
+    let r: Result<Foo, DebugFoo> = Ok(Foo);
+    assert!(r.is_ok(), "oops");
+
+    // test ok with unit error
+    let r: Result<Foo, ()> = Ok(Foo);
+    assert!(r.is_ok());
+
     // test temporary ok
     fn get_ok() -> Result<Foo, DebugFoo> {
         Ok(Foo)

tests/ui/assertions_on_result_states.rs

@@ -27,6 +27,14 @@ fn main() {
     let r: Result<Foo, Foo> = Ok(Foo);
     assert!(r.is_ok());
 
+    // test ok with some messages
+    let r: Result<Foo, DebugFoo> = Ok(Foo);
+    assert!(r.is_ok(), "oops");
+
+    // test ok with unit error
+    let r: Result<Foo, ()> = Ok(Foo);
+    assert!(r.is_ok());
+
     // test temporary ok
     fn get_ok() -> Result<Foo, DebugFoo> {
         Ok(Foo)

tests/ui/assertions_on_result_states.stderr

@@ -7,31 +7,31 @@ LL |     assert!(r.is_ok());
    = note: `-D clippy::assertions-on-result-states` implied by `-D warnings`
 
 error: called `assert!` with `Result::is_ok`
-  --> $DIR/assertions_on_result_states.rs:34:5
+  --> $DIR/assertions_on_result_states.rs:42:5
    |
 LL |     assert!(get_ok().is_ok());
    |     ^^^^^^^^^^^^^^^^^^^^^^^^^ help: replace with: `get_ok().unwrap()`
 
 error: called `assert!` with `Result::is_ok`
-  --> $DIR/assertions_on_result_states.rs:37:5
+  --> $DIR/assertions_on_result_states.rs:45:5
    |
 LL |     assert!(get_ok_macro!().is_ok());
    |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: replace with: `get_ok_macro!().unwrap()`
 
 error: called `assert!` with `Result::is_ok`
-  --> $DIR/assertions_on_result_states.rs:50:5
+  --> $DIR/assertions_on_result_states.rs:58:5
    |
 LL |     assert!(r.is_ok());
    |     ^^^^^^^^^^^^^^^^^^ help: replace with: `r.unwrap()`
 
 error: called `assert!` with `Result::is_ok`
-  --> $DIR/assertions_on_result_states.rs:56:9
+  --> $DIR/assertions_on_result_states.rs:64:9
    |
 LL |         assert!(r.is_ok());
    |         ^^^^^^^^^^^^^^^^^^ help: replace with: `r.unwrap()`
 
 error: called `assert!` with `Result::is_err`
-  --> $DIR/assertions_on_result_states.rs:64:5
+  --> $DIR/assertions_on_result_states.rs:72:5
    |
 LL |     assert!(r.is_err());
    |     ^^^^^^^^^^^^^^^^^^^ help: replace with: `r.unwrap_err()`