dart-fix-runtime-errors

Resolving Dart Static Analysis Errors

Contents

• Core Concepts & Guidelines
  • Type System & Soundness
  • Null Safety
  • Error Handling
• Workflows
  • Workflow: Static Analysis Resolution
• Examples

Core Concepts & Guidelines

Type System & Soundness

Enforce Dart's sound type system to prevent runtime invalid states.

• Method Overrides: Maintain sound return types (covariant) and parameter types (contravariant). Never tighten a parameter type in a subclass unless explicitly marked with the covariant keyword.
• Generics & Collections: Add explicit type annotations to generic classes (e.g., List<T>, Map<K, V>). Never assign a List<dynamic> to a typed list (e.g., List<Cat>).
• Downcasting: Avoid implicit downcasts from dynamic. Use explicit casts (e.g., as List<Cat>) when necessary, but ensure the underlying runtime type matches to prevent TypeError exceptions.
• Strict Casts: Enable strict-casts: true in analysis_options.yaml under analyzer: language: to force explicit casting and catch implicit downcast errors at compile time.

Null Safety

Eliminate static errors related to null safety by correctly managing variable initialization and nullability.

• Modifiers: Apply ? for nullable types, ! for null assertions, and required for named parameters that cannot be null.
• Late Initialization: Use the late keyword for non-nullable variables guaranteed to be initialized before use. Apply this specifically to top-level or instance variables where Dart's control flow analysis cannot definitively prove initialization.
• Wildcards: Use the _ wildcard variable (Dart 3.7+) for non-binding local variables or parameters to avoid unused variable warnings.

Error Handling

Distinguish between recoverable exceptions and unrecoverable errors.