dart-fix-runtime-errors

Run dart analyze to list errors, then use dart fix --apply to resolve standard lint issues automatically. Remaining errors require manual fixes based on type, such as adding null safety modifiers or explicit generic annotations.

Use the ? modifier for nullable types, ?. for optional chaining, ?? for fallbacks, and late for non-nullable variables initialized after declaration. Verify whether the variable can logically be null before choosing the approach.

Dart's sound type system requires contravariant parameter types, so a subclass cannot narrow a parameter type. Add the covariant keyword to the parameter when tightening the type is intentionally required by the domain logic.

Catch Exception subtypes for recoverable failures only. Never catch Error or its subtypes like TypeError, since they indicate programming bugs that must be fixed; enable the avoid_catching_errors linter rule to enforce this.

Setting strict-casts: true under analyzer language options forces explicit casting and catches implicit downcasts from dynamic at compile time. This prevents runtime TypeError exceptions caused by unchecked type assumptions.