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+A pattern attempted to extract an incorrect number of fields from a variant.
+
+Erroneous code example:
+
+```compile_fail,E0023
+enum Fruit {
+    Apple(String, String),
+    Pear(u32),
+}
+
+let x = Fruit::Apple(String::new(), String::new());
+
+match x {
+    Fruit::Apple(a) => {}, // error!
+    _ => {}
+}
+```
+
+A pattern used to match against an enum variant must provide a sub-pattern for
+each field of the enum variant.
+
+Here the `Apple` variant has two fields, and should be matched against like so:
+
+```
+enum Fruit {
+    Apple(String, String),
+    Pear(u32),
+}
+
+let x = Fruit::Apple(String::new(), String::new());
+
+// Correct.
+match x {
+    Fruit::Apple(a, b) => {},
+    _ => {}
+}
+```
+
+Matching with the wrong number of fields has no sensible interpretation:
+
+```compile_fail,E0023
+enum Fruit {
+    Apple(String, String),
+    Pear(u32),
+}
+
+let x = Fruit::Apple(String::new(), String::new());
+
+// Incorrect.
+match x {
+    Fruit::Apple(a) => {},
+    Fruit::Apple(a, b, c) => {},
+}
+```
+
+Check how many fields the enum was declared with and ensure that your pattern
+uses the same number.