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https://issues.apache.org/jira/browse/GROOVY-12397?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]
Paul King closed GROOVY-12397.
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> VerifyError for a pattern variable bound in a later &&/|| operand (JEP 394
> flow scoping)
> ----------------------------------------------------------------------------------------
>
> Key: GROOVY-12397
> URL: https://issues.apache.org/jira/browse/GROOVY-12397
> Project: Groovy
> Issue Type: Bug
> Affects Versions: 6.0.0-RC-1
> Reporter: Paul King
> Assignee: Paul King
> Priority: Major
> Fix For: 7.0.0-alpha-1, 6.0.0-RC-3
>
>
> Two related problems with JEP 394 {{instanceof}} pattern variables
> (GROOVY-12242), present in 6.0.0-RC-1.
> h3. 1. VerifyError for a pattern variable bound in a later {{&&}} / {{||}}
> operand
> A pattern variable declared in the right operand of {{&&}} or {{||}} has its
> slot allocated and null-initialised only at its own {{instanceof}} site. That
> operand is skipped when the left operand decides the result, so at the join
> the slot is undefined on one path and any later read of it (a following
> conjunct, the then branch) fails bytecode verification:
> {code:groovy}
> def trimmed(Object p) {
> if (p instanceof String s && s.length() > 0 && s.trim() instanceof String
> t) {
> return t
> }
> return null
> }
> trimmed(' ab ')
> {code}
> {noformat}
> java.lang.VerifyError: Bad local variable type
> {noformat}
> The same happens with {{||}}:
> {code:groovy}
> if (!(p instanceof String s) || s.isEmpty() || !(s.trim() instanceof String
> t)) return null
> return t
> {code}
> h3. 2. A pattern binding does not survive an if arm ending in {{break}} or
> {{continue}}
> JLS §14.22 says {{break}} and {{continue}} cannot complete normally, so per
> §6.3.2.2-200-C the other path's bindings are in scope after the {{if}}.
> {{VariableScopeVisitor}} and the if-statement writer only recognised
> {{return}}, {{throw}} and {{yield}}:
> {code:groovy}
> def upper(List items) {
> def out = []
> for (o in items) {
> if (!(o instanceof String s)) continue
> out << s.toUpperCase()
> }
> out
> }
> upper(['a', 1, 'b'])
> {code}
> {noformat}
> groovy.lang.MissingPropertyException: No such property: s for class: Script1
> {noformat}
> h3. Fix
> * {{BinaryExpressionHelper}} pre-declares the pattern variables of the right
> operand of {{&&}} / {{||}} before the left operand runs; the {{instanceof}}
> site reuses the pre-declared slot ({{CompileStack}} keeps the set).
> * {{VariableScopeVisitor}} and {{StatementWriter.writeIfElse}} use
> {{mayCompleteNormally}} for the "arm is abrupt" test, so {{break}} and
> {{continue}} count.
> Reproducer script covering all four cases (on 6.0.0-RC-1 it reports two
> VerifyErrors and two MissingPropertyExceptions):
> {code:groovy}
> // Save as patternSlots.groovy and run: groovy patternSlots.groovy
> def cases = [
> 'pattern variable bound in a later && operand': '''
> def trimmed(Object p) {
> if (p instanceof String s && s.length() > 0 && s.trim()
> instanceof String t) {
> return t
> }
> return null
> }
> assert trimmed(' ab ') == 'ab'
> assert trimmed('') == null
> assert trimmed(42) == null
> ''',
> 'pattern variable bound in a later || operand': '''
> def viaOr(Object p) {
> if (!(p instanceof String s) || s.isEmpty() || !(s.trim()
> instanceof String t)) {
> return null
> }
> return t
> }
> assert viaOr(' cd ') == 'cd'
> assert viaOr(42) == null
> ''',
> 'binding survives an if arm ending in continue': '''
> def upper(List items) {
> def out = []
> for (o in items) {
> if (!(o instanceof String s)) continue
> out << s.toUpperCase()
> }
> out
> }
> assert upper(['a', 1, 'b']) == ['A', 'B']
> ''',
> 'binding survives an if arm ending in break': '''
> def upper(List items) {
> def out = []
> for (o in items) {
> if (o !instanceof String s) break
> out << s.toUpperCase()
> }
> out
> }
> assert upper(['a', 'b', 1, 'c']) == ['A', 'B']
> ''',
> ]
> println "Groovy ${GroovySystem.version}"
> cases.each { name, source ->
> try {
> new GroovyShell().evaluate(source)
> println "PASS $name"
> } catch (Throwable t) {
> println "FAIL $name: ${t.class.simpleName}:
> ${t.message?.readLines()?.head()}"
> }
> }
> {code}
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