Header menu logo F# Compiler Guide

Names of entities and values in the F# Compiler

The F# tooling distinguishes between the following concepts of "name" for values, union cases, class/record fields and entities:

Specification of all logical names

The following tables loosely characterise the variations in logical names, how they correspond to F# source constructs and the SyntaxTree/TypedTree metadata for these.

Entities:

Display name in code

Logical name

Notes

C

C

type definition

C

C`1

e.g. generic type, see notes below for variations of display names

M

M

module definition

M

MModule

"ModuleSuffix" attribute for F# modules, now somewhat legacy, rarely used, but still allowed; also where "ModuleSuffix" is implied because type and module have the same name

JsonProvider<"foo.json">

JsonProvider,Schema=\"xyz\"

static parameters, see notes below for variations of display names

Values:

Display name in code

Relation

Logical name

Notes

(+)

 <-->

op_Addition

(+ )

-->

op_Addition

not reversed

op_Addition

-->

op_Addition

not reversed

(*)

 <-->

op_Multiply

( * )

-->

op_Multiply

not reversed

op_Multiply

-->

op_Multiply

not reversed

( *+ )

 <-->

op_MultiplyPlus

( *+ )

-->

op_MultiplyPlus

not reversed

op_MultiplyPlus

-->

op_MultiplyPlus

not reversed

(+++)

 <-->

op_PlusPlusPlus

op_PlusPlusPlus

-->

op_PlusPlusPlus

not reversed

(%)

 <-->

op_Modulus

op_Modulus

-->

op_Modulus

(?)

 <-->

op_Dynamic

not defined by default, for x?SomeThing

(?<-)

 <-->

op_DynamicAssignment

not defined by default, for x?SomeThing <- "a"

(..)

 <-->

op_Range

for "3 .. 5"

(.. ..)

 <-->

op_RangeStep

for "5 .. -1 .. 3"

or

 <-->

or

mod

 <-->

mod

let

 <-->

let

this is a keyword, in code it appears as let

type

 <-->

type

this is a keyword, in code it appears as type

base

 <-->

base

for IsBaseVal=true only. Base is a keyword, this is a special base val

base

 <-->

base

for IsBaseVal=false only. Base is a keyword, this is not a special base val

SomeClass

 <-->

.ctor

IsConstructor=true

.ctor

 <-->

.ctor

IsConstructor=false, this is only allowed for let-definitions, e.g. let .ctor x = 1
<-->

.cctor

IsClassConstructor=true, should never really appear in diagnostics or user-facing output

.cctor

 <-->

.cctor

IsClassConstructor=false, this is only allowed for let-definitions, e.g. let .cctor x = 1

(\|A\|_\|)

 <-->

\|A\|_\|

(\|A \|_ \|)

-->

\|A\|_\|

not reversed

P

 <-->

get_P

IsPropertyGetterMethod = true

P

 <-->

set_P

IsPropertySetterMethod = true

Other Val constructs less problematic for naming are:

Display name in code

Relation

Logical name

Notes

this

 <-->

this

IsCtorThisVal = true; From type C() as this; Can have any name, not particularly special with regard to names; This has a 'ref' type for initialization checks

this

 <-->

this

IsMemberThisVal = true; From member this.M() = ...; This can have a 'ref' type for initialization checks; Can have any name, not particularly special with regard to names

\

 <-->

System.IDisposable.Dispose

ImplementedSlotSigs is non-empty, i.e. length 1, should never really appear in diagnostics or user-facing output

Union cases:

Display name in code

Relation

Logical name

Notes

SomeCase | <--> | SomeCase ``Case with space`` | <--> | Case with space ``type`` | <--> | type | This is a keyword (::) | <--> | op_ColonColon | This is the logical name for the cons union case on FSharpList only [] | <--> | op_Nil | This is the logical name for the nil case on FSharpList only

Class and record fields, enum cases, active pattern cases, anonymous record fields:

Display name in code

Relation

Logical name

Notes

SomeField | <--> | SomeField ``Field with space``| <--> | Field with space ``type`` | <--> | type | This is a keyword

Generic parameters:

Display name in code

Relation

Logical name

Notes

'T | <--> | T '``T T T`` | <--> | T T T | BUG: the backticks are not currently added '``type`` | <--> | type | This is a keyword, BUG: the backticks are not currently added

Variations on display names

In different display settings, Entities/Types/Modules can have some variations on display names. For example, when showing some kinds of output we may set shortTypeNames=true which will never show full names.

Examples: - SomeNamespace.OtherNamespace.SomeType - ``Some Namespace With Spaces``.SomeType <-- BUG: not double-ticks today - `SomeEnclosingType<_>.SomeStaticMethod` <-- BUG: the mangled generic type counts are shown today

Compiled names

The name that appears in the .NET IL.

Affected by: - CompiledName attribute - some heuristics for generic type parameters

Also the name from signature is generally preferred; if there is any difference, a warning is emitted.

Example of how signature affects compiled names

Foo.fsi 

  val SomeFunction: x: int -> y: int -> int 

Foo.fs

  let SomeFunction a b = a + b // compiled name of parameters is x, y - warning emitted
Multiple items
val int: value: 'T -> int (requires member op_Explicit)

--------------------
type int = int32

--------------------
type int<'Measure> = int

Type something to start searching.