Details
Description
The new function API checks the types of given arguments and gives an error. This error is hard to understand in several situations:
- when a lambda is given where none is accepted since it only reports the given Callable type as if it was a regular parameter. It should call it out explicitly (since a Callable is an Object, it looks like the error is not legit). Calling the assert_type function with a lambda shows the bad error message.
- When a lambda is expected, but does not match
- Error spews out all details about the types (an array with thousands of entries is displayed)
We should implement an ExplainingTypeCalculator that:
- explains why a match failed
- is given the names of the input objects
- produces a message with a reference rooted at the given name that shows where the error was found (e.g. $x[key][3] - expected X, got Y)
- reduces the detailed type information in dependent types (e.g. Tuple, Array, Hash, Enum) such that repeated sequences are compacted (a sequence of 100 Integers may be displayed as Integer{100}
An error message now, may look like this:
Error while evaluating a Method call, function 'each' called with mis-matched arguments
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expected one of:
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each(Hash[Any, Any] hash, Callable[2, 2] block) - arg count {2}
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each(Hash[Any, Any] hash, Callable[1, 1] block) - arg count {2}
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each(Any enumerable, Callable[2, 2] block) - arg count {2}
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each(Any enumerable, Callable[1, 1] block) - arg count {2}
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actual:
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each(Tuple[Integer, Integer, Integer, Integer, Integer, Integer, Integer], Callable[Any, Any, Any]) - arg count {2} at line 1:29 on node foonode
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It takes a while to figure out that the error is that the given block to the each function had three parameters where 1 or 2 were expected.
If each expected result shows the reason for rejection are shown it would display something like:
Error while evaluating a Method call, function 'each' called with mis-matched arguments
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expected one of:
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each(Hash[Any, Any] hash, Callable[2, 2] block) - arg count {2}
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rejected: $block[parameter_count] is 3 where 2 was expected
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each(Hash[Any, Any] hash, Callable[1, 1] block) - arg count {2}
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rejected: $block[parameter_count] is 3 where 1 was expected
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each(Any enumerable, Callable[2, 2] block) - arg count {2}
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rejected: $block[parameter_count] is 3 where 2 was expected
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each(Any enumerable, Callable[1, 1] block) - arg count {2}
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rejected: $block[parameter_count] is 3 where 1 was expected
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actual:
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each(Tuple[Integer, Integer, Integer, Integer, Integer, Integer, Integer], Callable[Any, Any, Any]) - arg count {2} at line 1:29 on node foonode
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Or, it may be clearer if it does this:
Error while evaluating a Method call, function 'each' called with mis-matched arguments
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expected one of:
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1. each(Hash[Any, Any] hash, Callable[2, 2] block) - arg count {2}
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2. each(Hash[Any, Any] hash, Callable[1, 1] block) - arg count {2}
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3. each(Any enumerable, Callable[2, 2] block) - arg count {2}
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4. each(Any enumerable, Callable[1, 1] block) - arg count {2}
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actual:
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each(Tuple[Integer, Integer, Integer, Integer, Integer, Integer, Integer], Callable[Any, Any, Any]) - arg count {2} at line 1:29 on node foonode
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rejected because:
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1. $block[parameter_count] is 3 where 2 was expected
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2. $block[parameter_count] is 3 where 1 was expected
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3. $block[parameter_count] is 3 where 2 was expected
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4. $block[parameter_count] is 3 where 1 was expected
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And if we are able to detect a pattern (all caused by count being 3), we could point that out and at the end show:
rejected because:
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$block[parameter_count] is 3
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... and possibly the details 1-n
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Naturally, if there is only one signature, the numbering should be skipped.
Attachments
Issue Links
- is blocked by
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PUP-4438 Add required_repeated_param to 4.x function API
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- Closed
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- Closed
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- relates to
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PUP-2845 Move epp() and inline_epp() to 4x function API
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- Closed
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- Closed
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- Closed
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- Closed
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- links to
1.
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Create spec test for useful function call error message |
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Closed | Unassigned |