xo-expression type-inference [wip]

doc/notes.rst

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+Random notes.
+
+Type inference.
+
+Expressions represent parsed abstract syntax trees.
+We use the same data structure to represent syntax trees both before and after
+type inference.
+
+We record each Expression's type using a type_ref instance.
+A type_ref does two things:
+1. gives the expression's type a unique name
+2. records expression's concrete type once type infrerence has completed.
+
+Type inference resolves each Expression's type to a concrete TypeDescr.
+An Expression tree can't be compiled unless all reachable Expression nodes
+are resolved to concrete types, i.e. type inference has completed successfully.