Constants are current evaluated in a few places during closed world generation, primarily as part of the ScopeModelBuilder. The scope visitor was modifying the AST which meant we had to emit a new dill with these evaluated constants along with the closed world results.
This change instead evaluates the constants directly after linking the Kernel as part of the global transformations. This means we can update the ScopeModelBuilder to not mutate the AST at all as all constants are already simplified.
A potential follow up here is to simplify the ScopeModelBuilder since all nodes should already be simplified if they can be, we should be able to avoid visiting some children.
After this change we only directly create a single ConstantEvaluator, the one in `load_kernel`. The const simplifier also creates one and a follow up CL moves this to to run right after this new transformation.
Note: Alternate versions of this CL tried to make the global transformation simpler by either:
1) Running the const evaluator indiscriminately on all expressions. This didn't work because it lead to exponential computation on constants set up as a DAG (see tests/language/const/constant_dag_test).
2) Only evaluating ConstantExpression nodes to update UnevaluatedConstants. This does not cover all the cases where the ScopeModelBuilder is modifying the tree and lead to a different compiler output.
Change-Id: I746d889b37feddc9ab6c386c6252016dec745e6e
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/332601
Reviewed-by: Mayank Patke <fishythefish@google.com>
Nate Biggs
bebd08746b