Add another check

src/message.rs

@@ -27,26 +27,27 @@ pub enum Message {
         #[serde(with = "LocationDef")]
         location: Location,
     },
+    IfTuple {
+        filename: PathBuf,
+        #[serde(with = "LocationDef")]
+        location: Location,
+    },
 }
 
 impl Message {
     /// A four-letter shorthand code for the message.
     pub fn code(&self) -> &'static str {
         match self {
-            Message::ImportStarUsage {
-                filename: _,
-                location: _,
-            } => "F403",
+            Message::ImportStarUsage { .. } => "F403",
+            Message::IfTuple { .. } => "F634",
         }
     }
 
     /// The body text for the message.
     pub fn body(&self) -> &'static str {
         match self {
-            Message::ImportStarUsage {
-                filename: _,
-                location: _,
-            } => "Unable to detect undefined names",
+            Message::ImportStarUsage { .. } => "Unable to detect undefined names",
+            Message::IfTuple { .. } => "If test is a tuple, which is always `True`",
         }
     }
 }
@@ -65,6 +66,17 @@ impl fmt::Display for Message {
                 self.code().red().bold(),
                 self.body()
             ),
+            Message::IfTuple { filename, location } => write!(
+                f,
+                "{}{}{}{}{}\t{}\t{}",
+                filename.to_string_lossy().white().bold(),
+                ":".cyan(),
+                location.column(),
+                ":".cyan(),
+                location.row(),
+                self.code().red().bold(),
+                self.body()
+            ),
         }
     }
 }