3 files changed, 206 insertions, 12 deletions
diff --git a/tests/ui/empty_enum_variants_with_brackets.fixed b/tests/ui/empty_enum_variants_with_brackets.fixed
index 885f6a50025..abdf6ca5cb6 100644
--- a/tests/ui/empty_enum_variants_with_brackets.fixed
+++ b/tests/ui/empty_enum_variants_with_brackets.fixed
@@ -6,8 +6,7 @@ pub enum PublicTestEnum {
     NonEmptyParentheses(i32, i32),     // No error
     EmptyBraces,
     //~^ empty_enum_variants_with_brackets
-    EmptyParentheses,
-    //~^ empty_enum_variants_with_brackets
+    EmptyParentheses(), // No error as enum is pub
 }
 
 enum TestEnum {
@@ -20,6 +19,67 @@ enum TestEnum {
     AnotherEnum, // No error
 }
 
+mod issue12551 {
+    enum EvenOdd {
+        // Used as functions -> no error
+        Even(),
+        Odd(),
+        // Not used as a function
+        Unknown,
+        //~^ empty_enum_variants_with_brackets
+    }
+
+    fn even_odd(x: i32) -> EvenOdd {
+        (x % 2 == 0).then(EvenOdd::Even).unwrap_or_else(EvenOdd::Odd)
+    }
+
+    fn natural_number(x: i32) -> NaturalOrNot {
+        (x > 0)
+            .then(NaturalOrNot::Natural)
+            .unwrap_or_else(NaturalOrNot::NotNatural)
+    }
+
+    enum NaturalOrNot {
+        // Used as functions -> no error
+        Natural(),
+        NotNatural(),
+        // Not used as a function
+        Unknown,
+        //~^ empty_enum_variants_with_brackets
+    }
+
+    enum RedundantParenthesesFunctionCall {
+        // Used as a function call but with redundant parentheses
+        Parentheses,
+        //~^ empty_enum_variants_with_brackets
+        // Not used as a function
+        NoParentheses,
+    }
+
+    #[allow(clippy::no_effect)]
+    fn redundant_parentheses_function_call() {
+        // The parentheses in the below line are redundant.
+        RedundantParenthesesFunctionCall::Parentheses;
+        RedundantParenthesesFunctionCall::NoParentheses;
+    }
+
+    // Same test as above but with usage of the enum occurring before the definition.
+    #[allow(clippy::no_effect)]
+    fn redundant_parentheses_function_call_2() {
+        // The parentheses in the below line are redundant.
+        RedundantParenthesesFunctionCall2::Parentheses;
+        RedundantParenthesesFunctionCall2::NoParentheses;
+    }
+
+    enum RedundantParenthesesFunctionCall2 {
+        // Used as a function call but with redundant parentheses
+        Parentheses,
+        //~^ empty_enum_variants_with_brackets
+        // Not used as a function
+        NoParentheses,
+    }
+}
+
 enum TestEnumWithFeatures {
     NonEmptyBraces {
         #[cfg(feature = "thisisneverenabled")]
@@ -28,4 +88,18 @@ enum TestEnumWithFeatures {
     NonEmptyParentheses(#[cfg(feature = "thisisneverenabled")] i32), // No error
 }
 
+#[derive(Clone)]
+enum Foo {
+    Variant1(i32),
+    Variant2,
+    Variant3, //~ ERROR: enum variant has empty brackets
+}
+
+#[derive(Clone)]
+pub enum PubFoo {
+    Variant1(i32),
+    Variant2,
+    Variant3(),
+}
+
 fn main() {}
diff --git a/tests/ui/empty_enum_variants_with_brackets.rs b/tests/ui/empty_enum_variants_with_brackets.rs
index 092712ee2ea..63a5a8e9143 100644
--- a/tests/ui/empty_enum_variants_with_brackets.rs
+++ b/tests/ui/empty_enum_variants_with_brackets.rs
@@ -6,8 +6,7 @@ pub enum PublicTestEnum {
     NonEmptyParentheses(i32, i32),     // No error
     EmptyBraces {},
     //~^ empty_enum_variants_with_brackets
-    EmptyParentheses(),
-    //~^ empty_enum_variants_with_brackets
+    EmptyParentheses(), // No error as enum is pub
 }
 
 enum TestEnum {
@@ -20,6 +19,67 @@ enum TestEnum {
     AnotherEnum, // No error
 }
 
+mod issue12551 {
+    enum EvenOdd {
+        // Used as functions -> no error
+        Even(),
+        Odd(),
+        // Not used as a function
+        Unknown(),
+        //~^ empty_enum_variants_with_brackets
+    }
+
+    fn even_odd(x: i32) -> EvenOdd {
+        (x % 2 == 0).then(EvenOdd::Even).unwrap_or_else(EvenOdd::Odd)
+    }
+
+    fn natural_number(x: i32) -> NaturalOrNot {
+        (x > 0)
+            .then(NaturalOrNot::Natural)
+            .unwrap_or_else(NaturalOrNot::NotNatural)
+    }
+
+    enum NaturalOrNot {
+        // Used as functions -> no error
+        Natural(),
+        NotNatural(),
+        // Not used as a function
+        Unknown(),
+        //~^ empty_enum_variants_with_brackets
+    }
+
+    enum RedundantParenthesesFunctionCall {
+        // Used as a function call but with redundant parentheses
+        Parentheses(),
+        //~^ empty_enum_variants_with_brackets
+        // Not used as a function
+        NoParentheses,
+    }
+
+    #[allow(clippy::no_effect)]
+    fn redundant_parentheses_function_call() {
+        // The parentheses in the below line are redundant.
+        RedundantParenthesesFunctionCall::Parentheses();
+        RedundantParenthesesFunctionCall::NoParentheses;
+    }
+
+    // Same test as above but with usage of the enum occurring before the definition.
+    #[allow(clippy::no_effect)]
+    fn redundant_parentheses_function_call_2() {
+        // The parentheses in the below line are redundant.
+        RedundantParenthesesFunctionCall2::Parentheses();
+        RedundantParenthesesFunctionCall2::NoParentheses;
+    }
+
+    enum RedundantParenthesesFunctionCall2 {
+        // Used as a function call but with redundant parentheses
+        Parentheses(),
+        //~^ empty_enum_variants_with_brackets
+        // Not used as a function
+        NoParentheses,
+    }
+}
+
 enum TestEnumWithFeatures {
     NonEmptyBraces {
         #[cfg(feature = "thisisneverenabled")]
@@ -28,4 +88,18 @@ enum TestEnumWithFeatures {
     NonEmptyParentheses(#[cfg(feature = "thisisneverenabled")] i32), // No error
 }
 
+#[derive(Clone)]
+enum Foo {
+    Variant1(i32),
+    Variant2,
+    Variant3(), //~ ERROR: enum variant has empty brackets
+}
+
+#[derive(Clone)]
+pub enum PubFoo {
+    Variant1(i32),
+    Variant2,
+    Variant3(),
+}
+
 fn main() {}
diff --git a/tests/ui/empty_enum_variants_with_brackets.stderr b/tests/ui/empty_enum_variants_with_brackets.stderr
index a9ae3b476dd..7fe85e829a3 100644
--- a/tests/ui/empty_enum_variants_with_brackets.stderr
+++ b/tests/ui/empty_enum_variants_with_brackets.stderr
@@ -9,7 +9,15 @@ LL |     EmptyBraces {},
    = help: remove the brackets
 
 error: enum variant has empty brackets
-  --> tests/ui/empty_enum_variants_with_brackets.rs:9:21
+  --> tests/ui/empty_enum_variants_with_brackets.rs:15:16
+   |
+LL |     EmptyBraces {},
+   |                ^^^
+   |
+   = help: remove the brackets
+
+error: enum variant has empty brackets
+  --> tests/ui/empty_enum_variants_with_brackets.rs:17:21
    |
 LL |     EmptyParentheses(),
    |                     ^^
@@ -17,20 +25,58 @@ LL |     EmptyParentheses(),
    = help: remove the brackets
 
 error: enum variant has empty brackets
-  --> tests/ui/empty_enum_variants_with_brackets.rs:16:16
+  --> tests/ui/empty_enum_variants_with_brackets.rs:28:16
    |
-LL |     EmptyBraces {},
-   |                ^^^
+LL |         Unknown(),
+   |                ^^
    |
    = help: remove the brackets
 
 error: enum variant has empty brackets
-  --> tests/ui/empty_enum_variants_with_brackets.rs:18:21
+  --> tests/ui/empty_enum_variants_with_brackets.rs:47:16
    |
-LL |     EmptyParentheses(),
-   |                     ^^
+LL |         Unknown(),
+   |                ^^
+   |
+   = help: remove the brackets
+
+error: enum variant has empty brackets
+  --> tests/ui/empty_enum_variants_with_brackets.rs:53:20
+   |
+LL |         Parentheses(),
+   |                    ^^
+   |
+help: remove the brackets
+   |
+LL ~         Parentheses,
+LL |
+...
+LL |         // The parentheses in the below line are redundant.
+LL ~         RedundantParenthesesFunctionCall::Parentheses;
+   |
+
+error: enum variant has empty brackets
+  --> tests/ui/empty_enum_variants_with_brackets.rs:76:20
+   |
+LL |         Parentheses(),
+   |                    ^^
+   |
+help: remove the brackets
+   |
+LL ~         RedundantParenthesesFunctionCall2::Parentheses;
+LL |         RedundantParenthesesFunctionCall2::NoParentheses;
+...
+LL |         // Used as a function call but with redundant parentheses
+LL ~         Parentheses,
+   |
+
+error: enum variant has empty brackets
+  --> tests/ui/empty_enum_variants_with_brackets.rs:95:13
+   |
+LL |     Variant3(),
+   |             ^^
    |
    = help: remove the brackets
 
-error: aborting due to 4 previous errors
+error: aborting due to 8 previous errors