Add test for warning emitting if match is too complex

tests/ui/pattern/too_complex_match.rs

@@ -0,0 +1,75 @@
+//@ check-pass
+
+#[derive(Default)]
+struct BaseCommand {
+    field01: bool,
+    field02: bool,
+    field03: bool,
+    field04: bool,
+    field05: bool,
+    field06: bool,
+    field07: bool,
+    field08: bool,
+    field09: bool,
+    field10: bool,
+    field11: bool,
+    field12: bool,
+    field13: bool,
+    field14: bool,
+    field15: bool,
+    field16: bool,
+    field17: bool,
+    field18: bool,
+    field19: bool,
+    field20: bool,
+}
+
+fn request_key(command: BaseCommand) {
+    match command { //~ WARN: `match` is too complex
+        BaseCommand { field01: true, .. } => {}
+        BaseCommand { field02: true, .. } => {}
+        BaseCommand { field03: true, .. } => {}
+        BaseCommand { field04: true, .. } => {}
+        BaseCommand { field05: true, .. } => {}
+        BaseCommand { field06: true, .. } => {}
+        BaseCommand { field07: true, .. } => {}
+        BaseCommand { field08: true, .. } => {}
+        BaseCommand { field09: true, .. } => {}
+        BaseCommand { field10: true, .. } => {}
+        BaseCommand { field11: true, .. } => {}
+        BaseCommand { field12: true, .. } => {}
+        BaseCommand { field13: true, .. } => {}
+        BaseCommand { field14: true, .. } => {}
+        BaseCommand { field15: true, .. } => {}
+        BaseCommand { field16: true, .. } => {}
+        BaseCommand { field17: true, .. } => {}
+        BaseCommand { field18: true, .. } => {}
+        BaseCommand { field19: true, .. } => {}
+        BaseCommand { field20: true, .. } => {}
+
+        BaseCommand { field01: false, .. } => {}
+        BaseCommand { field02: false, .. } => {}
+        BaseCommand { field03: false, .. } => {}
+        BaseCommand { field04: false, .. } => {}
+        BaseCommand { field05: false, .. } => {}
+        BaseCommand { field06: false, .. } => {}
+        BaseCommand { field07: false, .. } => {}
+        BaseCommand { field08: false, .. } => {}
+        BaseCommand { field09: false, .. } => {}
+        BaseCommand { field10: false, .. } => {}
+        BaseCommand { field11: false, .. } => {}
+        BaseCommand { field12: false, .. } => {}
+        BaseCommand { field13: false, .. } => {}
+        BaseCommand { field14: false, .. } => {}
+        BaseCommand { field15: false, .. } => {}
+        BaseCommand { field16: false, .. } => {}
+        BaseCommand { field17: false, .. } => {}
+        BaseCommand { field18: false, .. } => {}
+        BaseCommand { field19: false, .. } => {}
+        BaseCommand { field20: false, .. } => {}
+    }
+}
+
+fn main() {
+    request_key(BaseCommand::default());
+}

tests/ui/pattern/too_complex_match.stderr

@@ -0,0 +1,14 @@
+warning: `match` is too complex
+  --> $DIR/too_complex_match.rs:28:5
+   |
+LL | /     match command {
+LL | |         BaseCommand { field01: true, .. } => {}
+LL | |         BaseCommand { field02: true, .. } => {}
+LL | |         BaseCommand { field03: true, .. } => {}
+...  |
+LL | |         BaseCommand { field20: false, .. } => {}
+LL | |     }
+   | |_____^
+
+warning: 1 warning emitted
+