Support patterns on arrays and opaque types. #878
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Closes #464 , #804
We add a phase to rewrite array patterns and usize/isize/i128/u128 patterns.
The phase rewrites them with
if let
guards.For integer types the idea is to rewrite:
as
For array/slice patterns, the idea is to rewrite:
as
In the case of slice patterns we also test the length of the slice in the condition:
becomes
In case the subpatterns of an array also need a guard to be rewritten, we rewrite using a pattern matching.
In case there is a disjunctive pattern with guards in the subpatterns, we try to take a boolean disjunction of the guards. When it is not possible we call the phase
hoist_disjunctive_patterns
and separate the arm into one arm for each case of the disjunction.