Error map
Type of expression is ambiguous Swift: Type of expression is ambiguous without a type annotation (more context)
iOS · layer 1, On your device
Centre: this error. First ring: errors it is linked with (12). 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 (12)
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.
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.
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.
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…
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…
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: Escaping closure captures mutating 'self' parameter
A mutating method of a struct tries to capture self in an escaping closure, which Swift forbids.
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.
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.
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.
Two steps away (24)
Swift: Could not cast value of type 'X' to 'Y'
A force cast (as!) failed because the object isn’t the expected type.
error NU1101: Unable to find package X. No packages exist with this id in source(s): nuget.org
NuGet restore can’t find the package in any configured source — typo, private feed not configured/authenticated, or nuget.org mis…
AmbiguousMatchException: The request matched multiple endpoints. Matches: X, Y
Two controller actions or minimal API endpoints have the same route and HTTP method.
Terraform: Error: Reference to undeclared resource / Reference to undeclared input variable
The configuration refers to a resource, data source, variable or module output that isn’t declared in this module.
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.
TypeError: x is not a function
You called something as a function, but its value is not a function (it’s undefined, a string, an object…).
ImportError: cannot import name 'x' from 'y'
The module was found, but the name you’re importing from it doesn’t exist — usually a version change or a circular import.
TypeError: x is not a constructor
new was used with something that isn’t a class/constructor — usually a wrong import.
TS2304: Cannot find name 'x'.
TypeScript doesn’t know an identifier — a missing import, missing type definitions (e.g. for Node or Jest globals), or a typo.
TS2339: Property 'x' does not exist on type 'Y'.
TypeScript’s type for the object doesn’t include that property.
TS2345: Argument of type 'string | undefined' is not assignable to parameter of type 'string'.
A value’s type doesn’t match the function parameter — commonly a possibly-undefined value passed where a definite one is required.
ReferenceError: x is not defined
Code refers to a variable or function name that doesn’t exist in the current scope.
NameError: name 'x' is not defined
Python doesn’t know the name — it was never assigned/imported in this scope, or it’s misspelled.
SyntaxError: Identifier 'x' has already been declared
The same let/const/class name was declared twice in the same scope.
ASP.NET Core: The antiforgery token could not be decrypted / The required antiforgery cookie is not present (400 Bad Request)
Form POST failed antiforgery validation — the token is missing, the cookie is missing, or Data Protection keys changed so old tok…
Swift: No such module 'X' (module not found)
Xcode can’t find a Swift package, pod or framework you import.
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…
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.
System.NullReferenceException: Object reference not set to an instance of an object
Code dereferenced a variable that is `null` — the .NET equivalent of Java’s NullPointerException.
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.
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