Throw an error when using derivimplicit with PROCEDURE block

[JCGoran]

The following modfile does not work with NOCMODL:

: mwe.mod
NEURON	{
	SUFFIX example
}

BREAKPOINT	{
    SOLVE myfunc METHOD derivimplicit
}

PROCEDURE myfunc() {}

With the error:

Error: Method derivimplicit can't be used with Block myfunc at line 10 in file mwe.mod

On the other hand, nmodl --neuron mwe.mod just segfaults with no useful error; with debugging symbols, I get a slightly more verbose backtrace:

Assertion failed: (node_to_solve->get_node_type() == ast::AstNodeType::DERIVATIVE_BLOCK), function create_solution_expression, file solve_block_visitor.cpp, line 59

This PR fixes it so it actually throws a runtime_error with the traceback:

terminating due to uncaught exception of type std::runtime_error: Method derivimplicit cannot be used for ProcedureBlock block myfunc

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 86.74%. Comparing base (86c2c66) to head (a14ffe2).

Additional details and impacted files

@@           Coverage Diff           @@
##           master    #1383   +/-   ##
=======================================
  Coverage   86.73%   86.74%           
=======================================
  Files         180      180           
  Lines       13675    13685   +10     
=======================================
+ Hits        11861    11871   +10     
  Misses       1814     1814           

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[1uc]

This could either be tested via Catch2 or we can setup a directory tests/invalid_mod_files to collect numerous invalid modfiles, that we run similarly to the usecases.

[bbpbuildbot]

Logfiles from GitLab pipeline #225660 (:no_entry:) have been uploaded here!

Status and direct links:

• ✅ spack_setup
• ✅ build:intel
• ✅ build:nvhpc
• ✅ test:intel
• ✅ test:nvhpc