Add better (helpful?) errors on mechanism semantic misuse. (#2171)

Tell users if they switch up `GLOBAL` and 'normal' `PARAMETER`s while
placing/painting.
Example
```
In [3]: d = A.decor(); d.paint('(all)', A.density('pas/g=17')); c = A.cable_cell(A.segment_tree(), d); s = A.single_cell_mod
   ...: el(c); s.run(1)
---------------------------------------------------------------------------
RuntimeError                              Traceback (most recent call last)
Cell In[3], line 1
----> 1 d = A.decor(); d.paint('(all)', A.density('pas/g=17')); c = A.cable_cell(A.segment_tree(), d); s = A.single_cell_model(c); s.run(1)

RuntimeError: mechanism 'pas' has no global parameter 'g', but a normal parameter with the same name exists. Set it via the parameter map, eg 'density("pas", {{"g", ...}, ...})'

In [7]: d = A.decor(); d.paint('(all)', A.density('pas', {'e':17})); t = A.segment_tree(); t.append(A.mnpos, (0, 0, 0, 1), (
   ...: 0, 0, 1, 1), 1); c = A.cable_cell(t, d); s = A.single_cell_model(c); s.run(1)
---------------------------------------------------------------------------
RuntimeError                              Traceback (most recent call last)
Cell In[7], line 1
----> 1 d = A.decor(); d.paint('(all)', A.density('pas', {'e':17})); t = A.segment_tree(); t.append(A.mnpos, (0, 0, 0, 1), (0, 0, 1, 1), 1); c = A.cable_cell(t, d); s = A.single_cell_model(c); s.run(1)

RuntimeError: mechanism 'pas' has no parameter 'e', but a global parameter with the same name exists. Use 'pas/e=...' to set it.
```

arbor/arbexcept.cpp

@@ -112,6 +112,26 @@ no_such_parameter::no_such_parameter(const std::string& mech_name, const std::st
  param_name(param_name)
 {}
 
+did_you_mean_global_parameter::did_you_mean_global_parameter(const std::string& mech_name, const std::string& param_name):
+ arbor_exception(pprintf("mechanism '{}' has no parameter '{}', "
+ "but a global parameter with the same name exists. "
+ "Use '{}/{}=...' to set it.",
+ mech_name, param_name,
+ mech_name, param_name)),
+ mech_name(mech_name),
+ param_name(param_name)
+{}
+
+did_you_mean_normal_parameter::did_you_mean_normal_parameter(const std::string& mech_name, const std::string& param_name):
+ arbor_exception(pprintf("mechanism '{}' has no global parameter '{}', "
+ "but a normal parameter with the same name exists. "
+ "Set it via the parameter map, eg 'density(\"{}\", {{\"{}\", ...}, ...})'",
+ mech_name, param_name,
+ mech_name, param_name)),
+ mech_name(mech_name),
+ param_name(param_name)
+{}
+
 illegal_diffusive_mechanism::illegal_diffusive_mechanism(const std::string& m, const std::string& i):
  arbor_exception(pprintf("mechanism '{}' accesses diffusive value of ion '{}', but diffusivity is disabled for it.", m, i)),
  mech{m},

arbor/fvm_layout.cpp

@@ -964,7 +964,14 @@ void verify_mechanism(const ion_species_map& global_ions,
  const mechanism_desc& desc) {
  const auto& name = desc.name();
  for (const auto& [p, v]: desc.values()) {
- if (!info.parameters.count(p)) throw no_such_parameter(name, p);
+ if (!info.parameters.count(p)) {
+ if (info.globals.count(p)) {
+ throw did_you_mean_global_parameter(name, p);
+ }
+ else {
+ throw no_such_parameter(name, p);
+ }
+ }
  if (!info.parameters.at(p).valid(v)) throw invalid_parameter_value(name, p, v);
  }
 

arbor/include/arbor/arbexcept.hpp

@@ -137,6 +137,18 @@ struct ARB_SYMBOL_VISIBLE no_such_parameter: arbor_exception {
  std::string param_name;
 };
 
+struct ARB_SYMBOL_VISIBLE did_you_mean_global_parameter: arbor_exception {
+ did_you_mean_global_parameter(const std::string& mech_name, const std::string& param_name);
+ std::string mech_name;
+ std::string param_name;
+};
+
+struct ARB_SYMBOL_VISIBLE did_you_mean_normal_parameter: arbor_exception {
+ did_you_mean_normal_parameter(const std::string& mech_name, const std::string& param_name);
+ std::string mech_name;
+ std::string param_name;
+};
+
 struct ARB_SYMBOL_VISIBLE illegal_diffusive_mechanism: arbor_exception {
  explicit illegal_diffusive_mechanism(const std::string& mech, const std::string& ion);
  std::string mech;

arbor/mechcat.cpp

@@ -292,17 +292,22 @@ struct catalogue_state {
 
  // Update global parameter values in info for derived mechanism.
 
- for (const auto& kv: global_params) {
- const auto& param = kv.first;
- const auto& value = kv.second;
-
+ for (const auto& [param, value]: global_params) {
  if (auto* p = ptr_by_key(new_info->globals, param)) {
  if (!p->valid(value)) {
  return unexpected_exception_ptr(invalid_parameter_value(name, param, value));
  }
  }
  else {
- return unexpected_exception_ptr(no_such_parameter(name, param));
+ if (new_info->parameters.count(param)) {
+ return unexpected_exception_ptr(
+ did_you_mean_normal_parameter(name.substr(0,
+ name.find('/')),
+ param));
+ }
+ else {
+ return unexpected_exception_ptr(no_such_parameter(name, param));
+ }
  }
 
  deriv.globals[param] = value;

test/unit/test_fvm_layout.cpp

@@ -1561,6 +1561,38 @@ TEST(fvm_layout, ion_weights) {
  }
 }
 
+TEST(fvm_layout, global_vs_range_parameters) {
+ soma_cell_builder builder(5);
+ builder.add_branch(0, 100, 0.5, 0.5, 1, "dend");
+
+ {
+ auto desc = builder.make_cell();
+ desc.decorations.paint("dend"_lab, density("pas", {{"e", 42}}));
+
+ EXPECT_THROW(
+ fvm_build_mechanism_data({},
+ {{desc}},
+ {0},
+ {{}},
+ fvm_cv_discretize({{desc}},
+ neuron_parameter_defaults)),
+ did_you_mean_global_parameter);
+ }
+ {
+ auto desc = builder.make_cell();
+ desc.decorations.paint("dend"_lab, density("pas/g=23"));
+
+ EXPECT_THROW(
+ fvm_build_mechanism_data({},
+ {{desc}},
+ {0},
+ {{}},
+ fvm_cv_discretize({{desc}},
+ neuron_parameter_defaults)),
+ did_you_mean_normal_parameter);
+ }
+}
+
 TEST(fvm_layout, revpot) {
  // Create two cells with three ions 'a', 'b' and 'c'.
  // Configure a reversal potential mechanism that writes to 'a' and