Adjust specification of evaluation order for instance getters returning a function #2182
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This CL adds a test of the evaluation order in the case where a function invocation `g(a)` or `r.g(a)` involves the invocation of a getter `g` that returns a function object, and that function object is invoked with an actual argument `a`. The expectation in the test is that evaluation occurs left-to-right in every case, with one exception: when `g` is a class instance getter (this does not apply to extension instance getters) the actual argument list is evaluated before the getter. This is the actually implemented behavior, and the specification is being updated to specify this behavior (cf. dart-lang/language#2182). ------- Old description: A piece of technical debt which has been around for several years is the fact that the specified left-to-right evaluation order isn't implemented everywhere. In particular, with an ordinary invocation like `r.m(a)` where `m` is a getter that returns a function, the argument is evaluated before the getter is called, which is not a left-to-right ordering. This CL adds a test (with 2 libraries) where the evaluation order is detected, such that we can decide how to proceed. Change-Id: Ia2619fe6b4c4cf4cec63bac9c9f834306bdefe52 Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/238903 Reviewed-by: Lasse Nielsen <lrn@google.com> Commit-Queue: Erik Ernst <eernst@google.com>
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Cf. dart-lang/sdk#36744.
This PR changes the language specification such that it specifies that the actual arguments are evaluated before the getter is invoked in the evaluation of an expression of the form
receiver.getter(arguments), in the case wheregetteris an instance getter. In all other cases we keep the currently specified (and implemented) semantics, which is to evaluate left-to-right, getter first and then actual arguments.This means that we will have an inconsistency in the language, but we avoid the breakage associated with the approach where all tools are changed to use a strict left-to-right evaluation order.