Coding standards and idioms

The F# compiler code base is slowly being updated to better coding standards. There is a long way to go.

The future work includes

[ ] Consistent use of fantomas formatting across as much of the codebase as feasible
[ ] Consistent naming conventions
[ ] Reduction in line length
[ ] Reduction in single-character identifiers
[ ] XML documentation for all types, members and cross-module functions

Abbreviations

The compiler codebase uses various abbreviations. Here are some of the most common ones.

Abbreviation	Meaning
`ad`	Accessor domain, meaning the permissions the accessing code has to access other constructs
`amap`	Assembly map, saying how to map IL references to F# CCUs
`arg`	Argument (parameter)
`argty`	Argument (parameter) type
`arginfo`	Argument (parameter) metadata
`ccu`	Reference to an F# compilation unit = an F# DLL (possibly including the DLL being compiled)
`celem`	Custom attribute element
`cenv`	Compilation environment. Means different things in different contexts, but usually a parameter for a single compilation state object being passed through a set of related functions in a single phase. The compilation state is often mutable.
`cpath`	Compilation path, meaning A.B.C for the overall names containing a type or module definition
`css`	Constraint solver state.
`denv`	Display Environment. Parameters guiding the formatting of types
`einfo`	An info object for an event (whether a .NET event, an F# event or a provided event)
`e`	Expression
`env`	Environment. Means different things in different contexts, but usually immutable state being passed and adjusted through a set of related functions in a single phase.
`finfo`	An info object for a field (whether a .NET field or a provided field)
`fref`	A reference to an ILFieldRef Abstract IL node for a field reference. Would normally be modernized to `ilFieldRef`
`g`	The TcGlobals value
`id`	Identifier
`lid`	Long Identifier
`m`	A source code range marker
`mimpl`	IL interface method implementation
`minfo`	An info object for a method (whether a .NET method, an F# method or a provided method)
`mk`	Means make in old fashioned F#/OCaml coding style
`modul`	a Typed Tree structure for a namespace or F# module
`pat`	Pattern, a syntactic AST node representing part of a pattern in a pattern match
`pinfo`	An info object for a property (whether a .NET property, an F# property or a provided property)
`rfref`	Record or class field reference, a reference to a Typed Tree node for a record or class field
`scoref`	The scope of a reference in IL metadata, either assembly, `.netmodule` or local
`sp`	Sequence points or debug points
`spat`	Simple Pattern, a syntactic AST node representing part of a pattern in a pattern match
`tau`	A type with the "forall" nodes stripped off (i.e. the nodes which represent generic type parameters). Comes from the notation 𝛕 used in type theory
`tcref`	Type constructor reference (an `EntityRef`)
`tinst`	Type instantiation
`tpenv`	Type parameter environment, tracks the type parameters in scope during type checking
`ty` (not: `typ`)	Type, usually a Typed Tree type
`tys` (not: `typs`)	List of types, usually Typed Tree types
`typar`	Type Parameter
`tyvar`	Type Variable, usually referring to an IL type variable, the compiled form of an F# type parameter
`ucref`	Union case reference, a reference to a Typed Tree node for a union case
`vref`	Value reference, a reference to a Typed Tree node for a value

Phase Abbreviation	Meaning
`Syn`	Abstract Syntax Tree
`Tc`	Type-checker
`IL`	Abstract IL = F# representation of .NET IL
`Ilx`	Extended Abstract IL = .NET IL plus a couple of constructs that get erased