In several flow analysis tests we need to model an expression with two
subexpressions, where the type of the overall expression is the same
as the type of the second subexpression.
Previously we did this using `ProtoStatement.thenExpr`, which created
a magic compound expression consisting of an expression (or statement)
followed by a second expression. This was too general, since it
allowed modelling code that would not be possible in Dart.
This CL replaces uses of `ProtoStatement.thenExpr` with a function
`second`, which models a Dart function defined this way:
T second(dynamic x, T y) => y;
This has two advantages:
- The tests are now modelling code that could actually exist in the
real world, rather than modelling pseudo-expressions that are not
actually possible to write in Dart.
- It prepares for a follow-up CL in which I'll be unifying the
representation of patterns and expressions in the flow analysis
tests; eliminating `ProtoStatement.thenExpr` will prevent a conflict
between it and `PossiblyGuardedPattern.thenExpr`.
With this change, two tests had to be deleted, because the conditions
they were testing could no longer be expressed:
- `for_conditionBegin() handles not-yet-seen variables`
- `whileStatement_conditionBegin() handles not-yet-seen variables`
This is ok, because these tests were designed to verify correct
behavior in the circumstance where the client forgets to declare a
variable. This circumstance no longer arises, because the
`_FlowAnalysisImpl` constructor detects undeclared variables and
generates synthetic declarations for them.
Change-Id: I19275ba0b7fa143ce7051bf14d0d4c6f57a4ab8e
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/315244
Commit-Queue: Paul Berry <paulberry@google.com>
Reviewed-by: Chloe Stefantsova <cstefantsova@google.com>
Paul Berry
64ecabdf16