A HParameterValue can be an SSA value or a mutable local variable
accessed via HLocalFet/HLocalSet. The latter happens in code that is not
completely SSA-converted (due to exception control flow).
The main bug is that the check on a mutable-variable-mode HParameterValue
should have been on a HLocalGet of the value, and not the HParameterValue
itself. This means that a reference to the HParameterValue cannot be
replaced with a strengthening check, as that breaks the invariant that
HLocalGet/Set refer to variables. There was code in types_propagation
that tried to work around this broken invariant.
The bug (issue 42189) required
- An elided instance method parameter
- try(-catch)(-finally) to avoid complete SSA-conversion
- -O0 to avoid optimizing away the check early with inferred types
The first attempt at a fix was to not check the elided parameter at all
since the default value is statically checked. This is still worthwhile.
Bug: 42189
Change-Id: Idd5e2b1485eba4950a36d1e4ff57ebe35e4c98a0
Fixed: 42189
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/150171
Reviewed-by: Sigmund Cherem <sigmund@google.com>
Commit-Queue: Stephen Adams <sra@google.com>
