SMT2 parser: use hash tables instead of if() ... else...

[kroening]

This refactors the SMT2 parser to use hash tables instead of chains of if()...else if()... for commands, sorts and expressions.

This enables extensions, and may have a performance benefit as the number of commands/expressions/sorts grows.

• Each commit message has a non-empty body, explaining why the change was made.
• 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/
• 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).
• My commit message includes data points confirming performance improvements (if claimed).
• My PR is restricted to a single feature or bugfix.
• n/a White-space or formatting changes outside the feature-related changed lines are in commits of their own.

[allredj]

⚠️
This PR failed Diffblue compatibility checks (cbmc commit: 0b4db94).
Build URL: https://travis-ci.com/diffblue/test-gen/builds/130035567
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.

[allredj]

✔️
Passed Diffblue compatibility checks (cbmc commit: 4ce9a7e).
Build URL: https://travis-ci.com/diffblue/test-gen/builds/130040813

[codecov-io]

Codecov Report

Merging #5143 into develop will increase coverage by 0.01%.
The diff coverage is 76.83%.

@@            Coverage Diff             @@
##           develop   #5143      +/-   ##
==========================================
+ Coverage    67.08%   67.1%   +0.01%     
==========================================
  Files         1149    1149              
  Lines        94035   94073      +38     
==========================================
+ Hits         63086   63123      +37     
- Misses       30949   30950       +1

Flag	Coverage Δ
#cproversmt2	42.77% <74.9%> (+0.04%)	⬆️
#regression	63.59% <72.97%> (+0.01%)	⬆️
#unit	31.94% <ø> (ø)	⬆️

Impacted Files	Coverage Δ
src/solvers/smt2/smt2_solver.cpp	83.01% <100%> (+1.13%)	⬆️
src/solvers/smt2/smt2_parser.h	100% <100%> (ø)	⬆️
src/solvers/smt2/smt2_parser.cpp	66.56% <74.57%> (+1.12%)	⬆️

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[allredj]

✔️
Passed Diffblue compatibility checks (cbmc commit: 2f7c9fb).
Build URL: https://travis-ci.com/diffblue/test-gen/builds/130524976

[polgreen]

This doesn't allow declaration of variables that have the same names as variables in function signatures, which would be allowed by SMT. e.g.,

(set-logic LIA)
(define-fun myfun ((x Int) (y Int)) Int
  (+ x y))
(declare-const x Int)

(assert (= (myfun x x)(+ x x )))
(check-sat)

[kroening]

This doesn't allow declaration of variables that have the same names as variables in function signatures, which would be allowed by SMT. e.g.,

Indeed; will make that a separate PR!

[allredj]

✔️
Passed Diffblue compatibility checks (cbmc commit: a8aa594).
Build URL: https://travis-ci.com/diffblue/test-gen/builds/130873673

[polgreen]

This doesn't allow declaration of variables that have the same names as variables in function signatures, which would be allowed by SMT. e.g.,

Indeed; will make that a separate PR!

I think the lack of local variable tracking may also affect let expressions

[polgreen]

Another failing case. Needs to expand function applications:

(set-logic LIA)
(define-fun myfun ((x Int) (y Int)) Int
  (+ x y))
(declare-const z Int)

(assert (= (myfun z z)(+ z z )))
(check-sat)

This invariant fails because the procedure isn't implemented for function_applications

--- begin invariant violation report ---
Invariant check failed
File: flattening/boolbv_width.cpp:196 function: get_entry
Condition: false
Reason: Unimplemented

[kroening]

I think the lack of local variable tracking may also affect let expressions

Indeed, added a test for that.

[kroening]

This invariant fails because the procedure isn't implemented for function_applications

The problem here is that we don't have an integer solver. The example works on bit-vectors.