Error map
Escaping closure captures mutating 'self' Swift: Escaping closure captures mutating 'self' parameter
iOS · layer 1, On your device
Centre: this error. First ring: errors it is linked with (9). Outer ring: what those are linked with. Colours show the layer of a request each error belongs to. Click any dot to re-centre the map on it; hover to follow its connections. The centre dot opens the error page.
Directly related (9)
Swift: The compiler is unable to type-check this expression in reasonable time; try breaking up the expression into distinct sub-expressions
A long expression (often in a SwiftUI body) has too many possible type combinations for the compiler — or hides a type error.
Swift: Cannot convert value of type 'X' to expected argument type 'Y'
The value’s type doesn’t match what the function or property expects.
SwiftUI: Publishing changes from background threads is not allowed; make sure to publish values from the main thread
An ObservableObject’s @Published property was updated from a background thread.
Swift: 'X' is only available in iOS 16.0 or newer
You used an API that requires a newer iOS than your deployment target.
Swift: Type of expression is ambiguous without a type annotation (more context)
The compiler can’t infer which type you mean — often because of a typo or a wrong argument elsewhere in the expression.
Swift: Reference to property 'x' in closure requires explicit use of 'self' to make capture semantics explicit
In an escaping closure inside a class, Swift requires self. to make the capture (and potential retain cycle) visible.
Swift 6: Main actor-isolated property 'x' can not be referenced from a nonisolated context / Sending 'x' risks causing data races
Strict concurrency checking found code that accesses main-actor state from another isolation domain, or passes non-Sendable value…
Swift: Fatal error: Index out of range
Code accessed an array index that doesn’t exist — empty arrays, off-by-one loops, or data changing while a table reloads.
Swift: Could not cast value of type 'X' to 'Y'
A force cast (as!) failed because the object isn’t the expected type.
Two steps away (21)
error CS0246: The type or namespace name 'X' could not be found (are you missing a using directive or an assembly reference?)
The compiler doesn’t know the type — missing using, missing NuGet package/project reference, or a target framework mismatch.
error CS0103: The name 'x' does not exist in the current context
The identifier isn’t declared in scope — typo, variable declared in another block, missing using static, or a Razor/partial class…
error CS1061: 'X' does not contain a definition for 'Y' and no accessible extension method 'Y' accepting a first argument of type 'X' could be found
The member you call doesn’t exist on that type — typo, wrong type, missing using for an extension method, or an API removed in a…
AttributeError: 'X' object has no attribute 'y'
You accessed an attribute or method that doesn’t exist on that object type.
java.lang.ClassCastException: class A cannot be cast to class B
An object was cast to a type it isn’t.
TS7016: Could not find a declaration file for module 'x'. 'x.js' implicitly has an 'any' type.
The JavaScript package has no TypeScript types bundled and no @types package installed.
Optimistic lock conflict: OptimisticLockException / StaleObjectStateException / version mismatch
Someone else changed the record after you read it, so your update — based on an old version — was rejected to avoid overwriting t…
API Error: Idempotency key reused with different parameters (idempotency_key_in_use)
An Idempotency-Key header was sent again with a different request body, or while the first request with that key was still runnin…
API Error: Too many concurrent requests (concurrency limit reached)
You have more requests in flight at once than the API allows for your key — even if your requests-per-minute rate is fine.
Swift: No such module 'X' (module not found)
Xcode can’t find a Swift package, pod or framework you import.
warning CS8618: Non-nullable property 'X' must contain a non-null value when exiting constructor. Consider declaring the property as nullable
With nullable reference types enabled, a non-nullable reference property isn’t initialised by the constructor.
Go: declared and not used: x / "fmt" imported and not used
Go refuses to compile code with unused local variables or unused imports.
Rust: error[E0308]: mismatched types — expected `X`, found `Y`
A value’s type doesn’t match what the context expects — common with &str vs String, Option/Result vs plain values, and integer ty…
Main Thread Checker: UI API called on a background thread: -[UIView setNeedsLayout]
UIKit was used from a background thread; UI must only be touched on the main thread.
Go: fatal error: all goroutines are asleep - deadlock!
Every goroutine is blocked waiting (on a channel, mutex or WaitGroup), so the program can never continue.
Fatal error: Unexpectedly found nil while unwrapping an Optional value
Swift force-unwrapped (`!`) an optional that was nil, crashing the app.
ArgumentOutOfRangeException: Index was out of range. Must be non-negative and less than the size of the collection
Code accessed a List/collection position that doesn’t exist (IndexOutOfRangeException for arrays).
.NET: Stack overflow. / Process is terminated due to StackOverflowException
Infinite or very deep recursion exhausted the thread’s stack; .NET can’t catch it and terminates the process.
Illegal instruction (core dumped) (SIGILL)
The program used a CPU instruction your processor doesn’t support — typically AVX/AVX2 in prebuilt binaries (TensorFlow, MongoDB…
The application was unable to start correctly (0xc0000142)
A DLL the program loads failed to initialise — often after an update, with corrupt runtimes, or when a desktop heap/session limit…
System.InvalidCastException: Unable to cast object of type 'X' to type 'Y'
An explicit cast failed because the object’s runtime type isn’t the target type.
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