Leave a Groovy def declaration alone instead of splicing var into its variable name.

[motlin]

What's changed?

DeclarationCheck.isSingleVariableDefinition now refuses declarations that expose no type expression for var to replace. The single guard covers UseVarForConstructors, UseVarForObject, UseVarForGenericsConstructors, and UseVarForGenericMethodInvocations.

What's your motivation?

The var recipes corrupt Groovy def declarations, non-idempotently.

// before
def newFile = new File(file.parentFile, newName)
assert file.renameTo(newFile) : "Failed to rename ${file} to ${newFile}"

// after one run
def varnewFile = new File(file.parentFile, newName)
assert file.renameTo(newFile) : "Failed to rename ${file} to ${newFile}"

// after a second run on the same file
def varvarnewFile = new File(file.parentFile, newName)

Originally hit on rewrite-migrate-java 3.42.1 with rewrite-maven-plugin 6.46.1, against a real
Maven archetype post-generate script. Still reproduces on main at v3.43.0.

Anything in particular you'd like reviewers to focus on?

Have you considered any alternatives or workarounds?

Applying an org.openrewrite.FindSourceFiles precondition of **/*.java to the var
recipes.

[motlin]

See also liftwizard/liftwizard#4125