use default

docs/tagged_union_pattern_in_typescript.md

@@ -94,8 +94,10 @@ class Expr {
                 return k.value;
             case "Add":
                 return k.right.eval() + k.left.eval();
-        }
+            default:
                 k satisfies never; // compile time exhaustiveness check
+                throw new Error("unexhausted"): // run time exhaustiveness check
+        }
     }
     // ...
 }
@@ -195,14 +197,15 @@ class Expr {
         const k = this.kind;
         switch (k.tag) {
             case "Int":
-                return;
+                break;
             case "Add":
                 k.left.visit(v);
                 k.right.visit(v);
-                return
-        }
+                break;
+            default:
                 k satisfies never;
         }
+    }
     // ...
 }
 ```

src/mir_interpreter.ts

@@ -157,10 +157,11 @@ class Val {
                 return `${k.value}`;
             case "Fn":
                 return `<${k.fn.ty.pretty()}>`;
-        }
+            default:
                 k satisfies never;
         }
     }
+}
 
 type ValKind =
     | { tag: "Void" }