tree 0d40d2e195e188753da25176bad3923d5bc7c4a3
parent 27ed7912af86426288107bfaa09b31c36099e4ba
author Jens Johansen <jensj@google.com> 1606825935 +0000
committer commit-bot@chromium.org <commit-bot@chromium.org> 1606825935 +0000

[VM] Read and report constant constructor coverage from dill

This CL makes use of the now included constant constructor coverage
in the dill file.

It works like this:
* When the CFE evaluates constants, every constant constructor
  invocation evaluated saves the reference to the constructor in the
  `Source` (from the Components uri to source table) for the callers
  Library.
* This data is loaded into the VM in a "raw" format.
* When a request for coverage comes in, the VM - on top of the normal
  coverage processing - goes through all scripts to find constant
  constructor coverage for the requested script and offset. Note that
  all scripts must be checked because library A can have evaluated a
  constructor from library B - so even if only coverage for library B
  was requested, library A has to be checked.
  For all constructors found the start and end position is reported as
  covered. Note that this does not mark any initializes and there are
  (at least currently) no good way of marking which initializes were
  evaluated (because it has to be stable across edits even when the
  `advanced invalidation feature` is enabled).
* Note that the reason for the coverage to work on references - as
  hinted above - is because we want it to be stable across hot reloads
  even if/when advanced invalidation is enabled. This means, that
  library A cannot record "positional coverage" for library B because
  library B might get (for instance) new comments that will make any old
  offsets invalid. By using references we always lookup in the current
  world and use the correct offsets.

https://github.com/dart-lang/sdk/issues/38934

TEST=Existing test suite, new tests for the new coverage added.

Change-Id: I925963d1a9b9907efe621c72deb7348fa3be5ae8
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/171949
Commit-Queue: Jens Johansen <jensj@google.com>
Reviewed-by: Ben Konyi <bkonyi@google.com>
Reviewed-by: Vyacheslav Egorov <vegorov@google.com>