[leonard84]

Spock's own @TempDir is the lifecycle-correct temporary directory: one per iteration by default, one per specification when combined with @Shared, and always deleted afterwards.
The alternatives leak.
@Rule TemporaryFolder is a JUnit 4 carry-over that only works through Spock's JUnit rule interop, and File.createTempDir() / Files.createTempDirectory(..) are never cleaned up unless somebody hand-writes a cleanup: block for them.

This rule reports both shapes in a Spock specification, with distinct messages, because the fixes differ in effort.

What is and is not reported

Reported:

• A @Rule or @ClassRule field whose type — or, for an untyped field, whose initializer — is TemporaryFolder.
• A call that creates a file or directory in the JVM-wide default temporary directory: File.createTempDir(..), File.createTempFile(prefix, suffix), Files.createTempDirectory(prefix, ..), Files.createTempFile(prefix, suffix, ..).
• new File(System.getProperty('java.io.tmpdir'), ..), including the concatenated System.getProperty('java.io.tmpdir') + '/x' form.

Not reported:

• A @TempDir field or parameter of any injectable type — Path, File, FileSystemFixture.
• The overloads that take an explicit target directory, e.g. Files.createTempFile(tempDir, 'a', 'b') or File.createTempFile('a', 'b', dir).
• Similarly named helpers on other receivers, such as fixtures.createTempDir() or FileUtils.createTempDirectory('x').
• Anything outside a Spock specification, including a helper class in the same file.

The ad-hoc creation shape can be switched off with checkAdHocCreation, which leaves only the TemporaryFolder fields reported.

Telling the overloads apart

The rule runs on the unresolved AST, so it matches the receiver textually against File and Files and tells the overloads apart by argument count: each explicit-directory overload takes one more argument than its default-directory sibling.
The exception is Files, whose default-directory overloads end in FileAttribute... varargs.
There a call with extra arguments is only reported when its first argument is a String literal or GString, as in Files.createTempDirectory('x', attribute).

Known limits

• A variable in that first position could hold either the prefix or the directory, so Files.createTempDirectory(prefix, attribute) stays silent.
• A static import (createTempDirectory('x')) or an aliased receiver is not recognized.

Implements #844