Disallow builtins as bound variables

1 files changed, 7 insertions, 5 deletions

diff --git a/dhall_parser/src/dhall.abnf b/dhall_parser/src/dhall.abnf
index d27554c..02edc84 100644
--- a/dhall_parser/src/dhall.abnf
+++ b/dhall_parser/src/dhall.abnf
@@ -168,11 +168,13 @@ quoted-label = 1*quoted-label-char
 

 ; NOTE: Dhall does not support Unicode labels, mainly to minimize the potential

 ; for code obfuscation

-; A label cannot not be any of the reserved identifiers for builtins (unless quoted).

+label = ("`" quoted-label "`" / simple-label)

+

+; An unreserved-label cannot not be any of the reserved identifiers for builtins (unless quoted).

 ; Their list can be found in semantics.md. This is not enforced by the grammar but

 ; should be checked by implementations. The only place where this restriction applies

 ; is bound variables.

-label = ("`" quoted-label "`" / simple-label)

+unreserved-label = label

 

 ; An any-label is allowed to be one of the reserved identifiers.

 any-label = label

@@ -541,7 +543,7 @@ expression =
     / annotated-expression

 

 ; "\(x : a) -> b"

-lambda-expression = lambda whitespace "(" whitespace label whitespace ":" nonempty-whitespace expression ")" whitespace arrow whitespace expression

+lambda-expression = lambda whitespace "(" whitespace unreserved-label whitespace ":" nonempty-whitespace expression ")" whitespace arrow whitespace expression

 

 ; "if a then b else c"

 ifthenelse-expression = if nonempty-whitespace expression then nonempty-whitespace expression else nonempty-whitespace expression

@@ -550,10 +552,10 @@ ifthenelse-expression = if nonempty-whitespace expression then nonempty-whitespa
 ; "let x     = e1 in e2"

 ; "let x = e1 let y = e2 in e3"

 let-expression = 1*let-binding in nonempty-whitespace expression

-let-binding = let nonempty-whitespace label whitespace [ ":" nonempty-whitespace expression ] "=" whitespace expression

+let-binding = let nonempty-whitespace unreserved-label whitespace [ ":" nonempty-whitespace expression ] "=" whitespace expression

 

 ; "forall (x : a) -> b"

-forall-expression = forall whitespace "(" whitespace label whitespace ":" nonempty-whitespace expression ")" whitespace arrow whitespace expression

+forall-expression = forall whitespace "(" whitespace unreserved-label whitespace ":" nonempty-whitespace expression ")" whitespace arrow whitespace expression

 

 ; "a -> b"

 arrow-expression = operator-expression arrow whitespace expression