getRestrictItem returns a lits of hints

[parsonsmatt]

This PR addresses #1647

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[parsonsmatt]

The naive approach given in this PR fails, as some rules can be more specific and unrestrict things. Local test output:

TEST FAILURE IN tests/_import_style_1
DIFFER ON LINE: 43
GOT : tests/importStyle-1.hs:6:1-51: Warning: HypotheticalModule3.OtherSubModule should be imported unqualified
WANT: 6 hints
FULL OUTPUT FOR GOT:
tests/importStyle-1.hs:1:1-26: Warning: Avoid restricted alias
Found:
  import HypotheticalModule1
Perhaps:
  import HypotheticalModule1 as HM1
Note: may break the code

tests/importStyle-1.hs:2:1-26: Warning: HypotheticalModule2 should be imported qualified or with an explicit import list
Found:
  import HypotheticalModule2
Perhaps:
  import qualified HypotheticalModule2
Note: may break the code

tests/importStyle-1.hs:3:1-26: Warning: HypotheticalModule3 should be imported qualified
Found:
  import HypotheticalModule3
Perhaps:
  import qualified HypotheticalModule3
Note: may break the code

tests/importStyle-1.hs:4:1-47: Warning: HypotheticalModule3.SomeModule should be imported unqualified
Found:
  import qualified HypotheticalModule3.SomeModule
Perhaps:
  import HypotheticalModule3.SomeModule
Note: may break the code

tests/importStyle-1.hs:5:1-47: Warning: HypotheticalModule3.SomeModule should be imported unqualified
Found:
  import HypotheticalModule3.SomeModule qualified
Perhaps:
  import HypotheticalModule3.SomeModule
Note: may break the code

tests/importStyle-1.hs:6:1-51: Warning: HypotheticalModule3.OtherSubModule should be imported post-qualified or unqualified
Found:
  import qualified HypotheticalModule3.OtherSubModule
Perhaps:
  import HypotheticalModule3.OtherSubModule qualified
Note: may break the code

tests/importStyle-1.hs:6:1-51: Warning: HypotheticalModule3.OtherSubModule should be imported unqualified
Found:
  import qualified HypotheticalModule3.OtherSubModule
Perhaps:
  import HypotheticalModule3.OtherSubModule
Note: may break the code

7 hints

.
TEST FAILURE IN tests/_import_style_2
DIFFER ON LINE: 1
GOT : tests/importStyle-2.hs:6:1-51: Warning: HypotheticalModule3.OtherSubModule should be imported unqualified
WANT: No hints
FULL OUTPUT FOR GOT:
tests/importStyle-2.hs:6:1-51: Warning: HypotheticalModule3.OtherSubModule should be imported unqualified
Found:
  import HypotheticalModule3.OtherSubModule qualified
Perhaps:
  import HypotheticalModule3.OtherSubModule
Note: may break the code

1 hint

Relevant import yaml:

- modules:
  - {name: HypotheticalModule1, as: HM1, asRequired: true}
  - {name: HypotheticalModule2, importStyle: explicitOrQualified}
  - {name: HypotheticalModule3, importStyle: qualified}
  - {name: 'HypotheticalModule3.*', importStyle: unqualified}
  - {name: 'HypotheticalModule3.OtherSubModule', importStyle: unrestricted, qualifiedStyle: post}
  - {name: HypotheticalModule4, importStyle: qualified, as: HM4, asRequired: true}
  - {name: HypotheticalModule5, importStyle: qualified, qualifiedStyle: post}

So the idea is that we'd have the direct match rule for HypotheticalModule3.OtherSubModule, and also the wildcard match for HypotheticalModule3.*, and then we sconcat those RestrictItems.

I'm updating my fix to do sconcat if there's an exact module name match, and to otherwise use a list of rules if it's just wildcard matches.

[parsonsmatt]

I've tested the patch on the reproduction repository and the patched version correctly reports the rule violation 🎉

[parsonsmatt]

Suggest reviewing with whitespace changes hidden

[parsonsmatt]

This preserves the old behavior: take the exact match and concat the rest of the rules into it.

[parsonsmatt]

In this branch, we had no exact match, meaning that wildcard contains all of the wildcard matches that hit. This means we have multiple wildcard rules that should be checked, and we probably don't want to combine these...

I can see some logic where "nested" rules should be combined, but totally disparate rules should not be. Like, Handler.** and Handler.Foo.** maybe should be combined because of the shared literal prefix. But **.*Spec and Handler.** should not, even though they have overlaps in Handler.FooSpec.