lix/src/libexpr/nixexpr-ast.def
Eelco Dolstra ca07f3e370 * Another experimental feature: a way to truly override attributes in
a rec.  This will be very useful to allow end-user customisation of
  all-packages.nix, for instance globally overriding GCC or some other
  dependency.  The // operator doesn't cut it: you could replace the
  "gcc" attribute, but all other attributes would continue to
  reference the original value due to the substitution semantics of
  rec.

  The syntax is a bit hacky but this is to allow backwards
  compatibility.
2008-08-14 16:59:37 +00:00

97 lines
2.9 KiB
Modula-2

init initNixExprHelpers
Pos | string int int | Pos |
NoPos | | Pos |
Function | Pattern Expr Pos | Expr |
Assert | Expr Expr Pos | Expr |
With | Expr Expr Pos | Expr |
If | Expr Expr Expr | Expr |
OpNot | Expr | Expr |
OpEq | Expr Expr | Expr |
OpNEq | Expr Expr | Expr |
OpAnd | Expr Expr | Expr |
OpOr | Expr Expr | Expr |
OpImpl | Expr Expr | Expr |
OpUpdate | Expr Expr | Expr |
SubPath | Expr Expr | Expr |
OpHasAttr | Expr string | Expr |
OpPlus | Expr Expr | Expr |
OpConcat | Expr Expr | Expr |
ConcatStrings | ATermList | Expr |
Call | Expr Expr | Expr |
Select | Expr string | Expr |
Var | string | Expr |
Int | int | Expr |
# Strings in the evaluator carry a so-called `context' (the ATermList)
# which is a list of strings representing store paths. This is to
# allow users to write things like
#
# "--with-freetype2-library=" + freetype + "/lib"
#
# where `freetype' is a derivation (or a source to be copied to the
# store). If we just concatenated the strings without keeping track
# of the referenced store paths, then if the string is used as a
# derivation attribute, the derivation will not have the correct
# dependencies in its inputDrvs and inputSrcs.
#
# The semantics of the context is as follows: when a string with
# context C is used as a derivation attribute, then the derivations in
# C will be added to the inputDrvs of the derivation, and the other
# store paths in C will be added to the inputSrcs of the derivations.
#
# For canonicity, the store paths should be in sorted order.
Str | string ATermList | Expr |
Str | string | Expr | ObsoleteStr
# Internal to the parser, doesn't occur in ASTs.
IndStr | string | Expr |
# A path is a reference to a file system object that is to be copied
# to the Nix store when used as a derivation attribute. When it is
# concatenated to a string (i.e., `str + path'), it is also copied and
# the resulting store path is concatenated to the string (with the
# store path in the context). If a string or path is concatenated to
# a path (i.e., `path + str' or `path + path'), the result is a new
# path (if the right-hand side is a string, the context must be
# empty).
Path | string | Expr |
List | ATermList | Expr |
BlackHole | | Expr |
Undefined | | Expr |
Removed | | Expr |
PrimOp | int ATermBlob ATermList | Expr |
Attrs | ATermList | Expr |
Closed | Expr | Expr |
Rec | ATermList ATermList | Expr |
Bool | ATermBool | Expr |
Null | | Expr |
Bind | string Expr Pos | ATerm |
Bind | string Expr | ATerm | ObsoleteBind
Inherit | Expr ATermList Pos | ATerm |
Scope | | Expr |
VarPat | string | Pattern |
AttrsPat | ATermList ATermBool | Pattern | # bool = `...'
AtPat | Pattern Pattern | Pattern |
Formal | string DefaultValue | ATerm |
DefaultValue | Expr | DefaultValue |
NoDefaultValue | | DefaultValue |
True | | ATermBool |
False | | ATermBool |
PrimOpDef | int ATermBlob | ATerm |
AttrRHS | Expr Pos | ATerm |
eTrue = makeBool(makeTrue())
eFalse = makeBool(makeFalse())
sOverrides = toATerm("__overrides")