Fix Issue 22039 - ICE on infinite recursion in default parameter

[RazvanN7]

When functionParameters is called, a pointer to the type of the call expression is passed so that the type is set. This is done because inout needs to be matched to one of the mutable, const, immutable qualifiers. As a measure of precaution, the first thing functionParameters does is to set that pointer to point to a TypeError. I guess this is done to catch any error that falls between the cracks, however, the downside is that you might end up with errors in your AST for which you have not outputted an error message.

This mechanism interferes with how default arguments are processed in the provided bug report:

int func(int x = func()) { return x; }

When the type of function func is analyzed, it needs to check that the type of the default arg matches the type of the parameter. As a consequence it performs semantic analysis on the function call of func. Then it ends up calling functionParameters with the type of function func (int(int x = func())) and a pointer to the type of the call expression. The catch is that this pointer points to a part of the type of func, therefore, when the pointer is set to TypeError the type of func is automatically updated to contain an error that is unaccounted for. This messes up the analysis of the default arg inside functionParameters and leads to the error being caught somewhere down the road where the compiler has no idea where it comes from, hence the ICE.

To fix this, I am deleting the line that bluntly sets the call type to error and if a default argument is missing its type information I'm just performing semantic on it on the spot. This seems to fix the issue and correctly output the recursive evaluation error.

Anyway, I find that functionParameteres is a complex beast doing all kinds of stuff. In my opinion, the way inout is handled here and how it uglifies the code is another justification for deprecating inout.

Although this is a regression, I'm not targeting stable since it's possible that some erroneous cases that would have been caught by the older mechanism slip through. Let's see what the tester says.

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Bugzilla references

Auto-close	Bugzilla	Severity	Description
✓	22039	regression	ICE on infinite recursion in default parameter

Testing this PR locally

If you don't have a local development environment setup, you can use Digger to test this PR:

dub run digger -- build "stable + dmd#14934"

[thewilsonator]

ICEs should go to stable though

[RazvanN7]

I think this PR has a certain level of risk, therefore it should be in master for a while.

As per @ibuclaw 's suggestion, retarget to stable.

[RazvanN7]

Documentation failure is unrelated.

[RazvanN7]

Stable seems to be broken for MacOS. I am seeing the failure on multiple PRs.