poset: to_dot also draw isolated nodes

Signed-off-by: Jean Privat <jean@pryen.org>
modelbuilder: do not resolve virtual types to early

virtual type are inherited thus require that the hierarchy is computed.
Thus, for formal bounds and super types, we must not try to look for
virtual types.

Signed-off-by: Jean Privat <jean@pryen.org>
modelbuilder: split extract `parse` from `parse_and_build`

Signed-off-by: Jean Privat <jean@pryen.org>
modelbuilder: `build_classes` do not call `build_properties`

Signed-off-by: Jean Privat <jean@pryen.org>
modelbuilder: ToolContext knows the modelbuilder

This is a step to downgrade modelbuilder in favor of toolcontext as
the main over-lord object.

Signed-off-by: Jean Privat <jean@pryen.org>
src: add phase.nit & frontend.nit

Also convert all phases of exprbuilder.nit

Signed-off-by: Jean Privat <jean@pryen.org>
src: remove useless exprbuilder.nit

Signed-off-by: Jean Privat <jean@pryen.org>
modelbuilder: use phases to build the model

Signed-off-by: Jean Privat <jean@pryen.org>
phases: add example div_by_zero.nit

Signed-off-by: Jean Privat <jean@pryen.org>
modelbuilder: remove `parse_and_build` and `build_all_classes`

Just rely on phases to perform the work.

Signed-off-by: Jean Privat <jean@pryen.org>
src: extract modelize_property.nit from modelbuiler.nit

Signed-off-by: Jean Privat <jean@pryen.org>
src: extract modelize_class.nit from modelbuiler.nit

Signed-off-by: Jean Privat <jean@pryen.org>
Merge branch 'phases'