These tests demonstrates a problem where the types to a module input are
not checked. For example, if a module - inner - defines a variable
"should_be_a_map" as a map, or with a default variable of map, we do not
fail if the user sets the variable value in the outer module to a string
value. This is also a problem in nested modules.
The implementation changes add a type checking step into the graph
evaluation process to ensure invalid types are not passed.
d7d39702c0