RFR: 8267578: Remove unnecessary preview checks

[Guoxiong Li]

Hi all,

The following preview checks are unnecessary because they are standard features now.

Attr.java

        allowReifiableTypesInInstanceof =
                Feature.REIFIABLE_TYPES_INSTANCEOF.allowedInSource(source) &&
                (!preview.isPreview(Feature.REIFIABLE_TYPES_INSTANCEOF) || preview.isEnabled());


JavacParser.java

        this.allowYieldStatement = (!preview.isPreview(Feature.SWITCH_EXPRESSION) || preview.isEnabled()) &&
                Feature.SWITCH_EXPRESSION.allowedInSource(source);


Resolve.java

        allowYieldStatement = (!preview.isPreview(Feature.SWITCH_EXPRESSION) || preview.isEnabled()) &&
                Feature.SWITCH_EXPRESSION.allowedInSource(source);


It is good to remove them.
Thanks for review.

Best Regards,
-- Guoxiong

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Commit messages:
 - 8267578: Remove unnecessary preview checks

Changes: https://git.openjdk.java.net/jdk/pull/4157/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=4157&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8267578
  Stats: 10 lines in 3 files changed: 0 ins; 7 del; 3 mod
  Patch: https://git.openjdk.java.net/jdk/pull/4157.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/4157/head:pull/4157

PR: https://git.openjdk.java.net/jdk/pull/4157