Add regression test for TG-2479

[yumibagge]

Add a test that failed initially and fixed by smowton/cbmc/smowton/feature/synthesise-lambda-classes

• Each commit message has a non-empty body, explaining why the change was made.
• n/a Methods or procedures I have added are documented, following the guidelines provided in CODING_STANDARD.md.
• n/a The feature or user visible behaviour I have added or modified has been documented in the User Guide in doc/cprover-manual/
• n/a Regression or unit tests are included, or existing tests cover the modified code (in this case I have detailed which ones those are in the commit message).
• n/a My commit message includes data points confirming performance improvements (if claimed).
• My PR is restricted to a single feature or bugfix.
• White-space or formatting changes outside the feature-related changed lines are in commits of their own.

[codecov-io]

Codecov Report

Merging #5006 into develop will decrease coverage by 0.01%.
The diff coverage is n/a.

@@             Coverage Diff             @@
##           develop    #5006      +/-   ##
===========================================
- Coverage    69.44%   69.43%   -0.02%     
===========================================
  Files         1310     1310              
  Lines       108753   108736      -17     
===========================================
- Hits         75523    75497      -26     
- Misses       33230    33239       +9

Impacted Files	Coverage Δ
src/solvers/strings/string_builtin_function.h	75.26% <0%> (-2.16%)	⬇️
src/analyses/goto_check.cpp	78.85% <0%> (-0.61%)	⬇️
src/ansi-c/expr2c.cpp	67.39% <0%> (-0.5%)	⬇️
src/goto-programs/builtin_functions.cpp	45.45% <0%> (-0.32%)	⬇️
src/ansi-c/c_typecheck_type.cpp	76% <0%> (-0.13%)	⬇️
src/solvers/strings/string_refinement.cpp	88.24% <0%> (-0.05%)	⬇️
src/goto-symex/goto_symex_state.h	100% <0%> (ø)	⬆️
src/solvers/strings/string_dependencies.h	100% <0%> (ø)	⬆️
src/ansi-c/scanner.l	63.91% <0%> (ø)	⬆️
src/ansi-c/c_typecheck_base.h	100% <0%> (ø)	⬆️
... and 4 more

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update 7ef8430...8a56cab. Read the comment docs.

[allredj]

⚠️
This PR failed Diffblue compatibility checks (cbmc commit: 0db7ffa).
Build URL: https://travis-ci.com/diffblue/test-gen/builds/122813182
Status will be re-evaluated on next push.
Common spurious failures include: the cbmc commit has disappeared in the mean time (e.g. in a force-push); the author is not in the list of contributors (e.g. first-time contributors); compatibility was already broken by an earlier merge.

[smowton]

assert true? Assert something nontrivial that you expect to pass instead.

[allredj]

⚠️
This PR failed Diffblue compatibility checks (cbmc commit: 8a56cab).
Build URL: https://travis-ci.com/diffblue/test-gen/builds/122860324
Status will be re-evaluated on next push.
Common spurious failures include: the cbmc commit has disappeared in the mean time (e.g. in a force-push); the author is not in the list of contributors (e.g. first-time contributors); compatibility was already broken by an earlier merge.

[yumibagge]

@LAJW @smowton, the assertions are pretty much from Lukasz's but hopefully this is now satisfactory. Please review.

[allredj]

✔️
Passed Diffblue compatibility checks (cbmc commit: 4b296f2).
Build URL: https://travis-ci.com/diffblue/test-gen/builds/124743538