Scott Murphy Heiberg created GROOVY-12715:
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Summary: A cast applied to await or to an async closure is parsed
as a call to a method named await or async
Key: GROOVY-12715
URL: https://issues.apache.org/jira/browse/GROOVY-12715
Project: Groovy
Issue Type: Bug
Components: parser-antlr4
Affects Versions: 6.0.0
Environment: Groovy 6.0.0 binary distribution and master 7379c5720d;
BellSoft JDK 21.0.12; macOS 15 arm64
Reporter: Scott Murphy Heiberg
{{await}} and {{async}} are contextual keywords with their own alternatives in
the {{expression}} rule of the grammar ({{awaitExprAlt}},
{{asyncClosureExprAlt}}), but the operand of a cast is parsed by
{{castOperandExpression}}, which lists only another cast, a
{{postfixExpression}} and the unary operators. So after a cast the two words
fall back to being identifiers, and {{(BigDecimal) await(price)}} is a call to
a method named {{await}} with one argument, {{(Awaitable<Integer>) async { 7
}}} a call to a method named {{async}} with a closure. At script level that is
a {{MissingMethodException}}; inside an async task the exception is swallowed
by the task nobody awaits, and the code awaiting the task's result hangs.
On 6.0.0 and master (JDK 21):
{code:groovy}
def t = async { 7 }
Integer a = (Integer) await t // MissingMethodException: No signature
of method: await for class: Script1 ... (groovy.concurrent.Awaitable)
{code}
{code:groovy}
import groovy.concurrent.Awaitable
Awaitable<Integer> t = (Awaitable<Integer>) async { 7 } //
MissingMethodException: ... async ... (Script1$_run_closure1)
{code}
{code:groovy}
import groovy.concurrent.DataflowVariable
DataflowVariable<BigDecimal> price = new DataflowVariable<BigDecimal>()
DataflowVariable<Integer> quantity = new DataflowVariable<Integer>()
DataflowVariable<BigDecimal> total = new DataflowVariable<BigDecimal>()
async {
BigDecimal unitPrice = (BigDecimal) await(price) // parsed as
this.await(price): the task fails
Integer count = (Integer) await(quantity)
total << unitPrice * count
}
async { quantity << 4 }
async { price << 2.50 }
println await(total) // hangs: total is never
bound
{code}
The parenthesised forms {{(int) (await t)}} and {{-(await t)}} work, as do
{{BigDecimal b = await(price)}} and {{await(price) as BigDecimal}}. Found
because Claude Opus 5.5 wrote the cast form in every answer of an eval task
under static typing; the script then timed out.
Suggested fix: add the {{asyncClosureExprAlt}} and {{awaitExprAlt}}
alternatives to {{castOperandExpression}} (it uses {{options { baseContext =
expression; }}}, so the same labels reuse the same contexts and
{{AstBuilder.visitAwaitExprAlt}} and {{visitAsyncClosureExprAlt}} apply
unchanged). Pull request to follow.
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