MGrammar + MSchema example

Justin asked a question about what it means to bring MSchema nad MGrammar together. Let me do a simple example to clarify.

Today I can write my semantic model in MSchema as such:

module Contacts {
type Person { Name : Text; Age : Integer32; }
People : Person*;
}

I can then write a grammar like this to generate values like this:

module Contacts {
language PeopleLang {
{
syntax Main = p:Person* => People { valuesof(p) };
syntax Person = n:Name a:Age => { Name = n, Age = a};
// elided details
}
}

There's a bunch of things that come to mind with the MGraph produced by the DSL versus the values expected by the semantic model, such as:
Type Checking
How do we statically (or dynamically) check that the values are typed correctly. For example, I want to do something like this:

syntax Person = n:Name a:Age => { Name = n : Text, Age = a : Integer32} : Contacts.Person ;

Expression support
I can build values up in MSchema using expressions and querys. Shouldn't I be able to do that on the RHS of grammars? For example:

syntax Name = f:FirstName l:LastName=> f + " " + l;

I also want to use functions and other things in the semantic model to both construct values as well as validate structural correctness.

Constraint support
Semantic models have constraints. Shouldn't values produced by MGrammar be validated against those? This is really a superset of the type check question since typing is really a form of constraint checking the structure of a value.


So, when I talked about MSchema and MGrammar integration in previous posts, I was hinting at the idea of bringing together the semantic model with the DSL declarations to ensure that the DSL output aligns with the model.

I hope that helps.