codeconsole opened a new pull request, #3148:
URL: https://github.com/apache/groovy/pull/3148
Under `@CompileStatic`, `++` and `--` on a non-primitive property or
subscript element evaluated the operand twice:
```groovy
@groovy.transform.CompileStatic
class Box {
int gets = 0
BigDecimal d = 1
BigDecimal getD() { gets++; d }
void setD(BigDecimal v) { d = v }
}
@groovy.transform.CompileStatic
def m() { def b = new Box(); b.d++; [b.gets, b.@d] }
assert m() == [1, 2] // was [2, 2]
```
For a subscript such as `list[idx++]++` on a `List<Integer>`, the receiver
and index expressions ran again too, so the incremented value of the next
element was stored into the first one (`[2, [21, 20], 10]` instead of `[1, [11,
20], 10]`). Dynamic Groovy and `@TypeChecked` read the operand once. 4.0.33,
5.0.8 and 6.0.0 behave the same.
When STC has resolved `next()`/`previous()`,
`StaticTypesBinaryExpressionMultiTypeDispatcher.writePostOrPrefixMethod` popped
the value already loaded and called the method on the operand expression again.
It now stores that value in a temporary and makes the call on it, with the same
method target, as `emitCompoundAssignCall` in the same class does. Postfix
still yields the old value and prefix the new one. Primitive operands and the
dynamic and `@TypeChecked` code generation are unchanged.
This and #3145 (GROOVY-12619, receiver of a compound-assigned or incremented
property evaluated once) touch different files; together, `obj().d++` evaluates
both the receiver and the getter once.
## Tests
The new tests in `STCAssignmentTest` run under `@TypeChecked` and, through
`AssignmentsStaticCompileTest`, under `@CompileStatic`. Four of them fail under
`@CompileStatic` without the change:
`testPostfixAndPrefixOnPropertyCallGetterOnce`,
`testPostfixAndPrefixOnPropertyCallGetterOnce2`,
`testPostfixAndPrefixOnSubscriptCallGetAtOnce` and
`testPostfixAndPrefixOnSubscriptEvaluateIndexOnce`. Between them they cover
wrapper, BigDecimal, String, Character and custom `next()` properties, static
properties, closures, lambdas, safe navigation, a custom getAt/putAt, and lists
and arrays with a side-effecting index. `testPostfixAndPrefixOnLocalVariable`
guards locals. The `groovy.transform.stc`, `org.codehaus.groovy.classgen.asm`
(including `.sc`), `gls`, `groovy.bugs` and `groovy.operator` packages pass.
The Checkstyle and CodeNarc gates pass.
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