The compiler is unable to type-check this expression in reasonable time Error

Question

JayDeveloper OP

Created Nov ’22

Replies 2

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Participants 2

I need help, I've never have seen this error before Could Someone help me?

Error: The compiler is unable to type-check this expression in reasonable time; try breaking up the expression into distinct sub-expressions

Answered by DTS Engineer in 737620022

In general, you get this error when type inference for an expression involves much-overloaded operations (such as +), so the compiler has a lot of possibilities to check. In general, you work around these by breaking the expression into parts, assigning the partial results to local variables, and then combining the local variables into your final expression value.

Since you've tagged this question with "SwiftUI", I'm guessing that you're actually getting this error inside a SwiftUI result builder, such as a View's body. In that case, it's the same problem from the compiler's point of view (the result builder is too complicated), but not from yours…

When you type something in your result builder that's not going to compile successfully, even something simple like using the wrong variable name or even not unwrapping an optional, you end up with an expression that the compiler doesn't know the type of. The compiler tries type inference as usual, and there can be two outcomes:

The compiler tries all possibilities and still fails to infer the type, in which case you get a suitable error message.
The compiler runs out of time before trying all the possibilities, in which case you get the "unable to type-check this expression in reasonable time" error.

Unfortunately, in case 2, the compiler is unable to tell you where in your code the error was detected. You'll need to do some sleuthing to find out. For example, you can try commenting out parts of the result builder to see what compiles and what doesn't. Sometimes you'll need to modify the code slightly (and temporarily) to make the remaining parts compile.

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Answer 1

JayDeveloper OP

Nov ’22

Im using Xcode 14.1.

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Answer 2

DTS Engineer OP

Apple

Nov ’22

Accepted Answer

In general, you get this error when type inference for an expression involves much-overloaded operations (such as +), so the compiler has a lot of possibilities to check. In general, you work around these by breaking the expression into parts, assigning the partial results to local variables, and then combining the local variables into your final expression value.

Since you've tagged this question with "SwiftUI", I'm guessing that you're actually getting this error inside a SwiftUI result builder, such as a View's body. In that case, it's the same problem from the compiler's point of view (the result builder is too complicated), but not from yours…

When you type something in your result builder that's not going to compile successfully, even something simple like using the wrong variable name or even not unwrapping an optional, you end up with an expression that the compiler doesn't know the type of. The compiler tries type inference as usual, and there can be two outcomes:

The compiler tries all possibilities and still fails to infer the type, in which case you get a suitable error message.
The compiler runs out of time before trying all the possibilities, in which case you get the "unable to type-check this expression in reasonable time" error.

Unfortunately, in case 2, the compiler is unable to tell you where in your code the error was detected. You'll need to do some sleuthing to find out. For example, you can try commenting out parts of the result builder to see what compiles and what doesn't. Sometimes you'll need to modify the code slightly (and temporarily) to make the remaining parts compile.

0