Ensure that the code for expect_correction is valid syntax

[Earlopain]

Issues found with this:

• Fix wrong autocorrect for Style/GuardClause when using heredoc without else branch #13211
• Fix wrong autocorrect for Style/MethodCallWithArgsParentheses with EnforcedStyle: omit_parentheses and whitespace #13215
• Fix wrong autocorrect for Lint/BigDecimalNew when using ::BigDecimal.new #13216
• Fix a false positive for Style/ArgumentForwarding with Ruby 3.0 and optional position arguments #13219
• Fix false positives for Style/OperatorMethodCall with named forwarding #13224
• Wrong autocorrect for Style/OperatorMethodCall with foo./(bar) #13225 (pending, couldn't figure it out)

I checked some repos in the rubocop org and they seem to not be affected by this change

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[bbatsov]

Hmm, how will this change help in practice? In our tests we obviously have only examples that result in valid syntax. The problem have always been the cases we didn't consider (and test).

[Earlopain]

In our tests we obviously have only examples that result in valid syntax

That's the plan, sure. But when I added this out of curiosity I found 5 cops that were checking against invalid code in some tests, see the linked PRs.

This doesn't do as much as it could since it only checks one ruby version and behaviour could have changed in subsequent/previous ones, but since it catched some issues this makes sense I think.

[bbatsov]

Agreed.