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authorstuebinm2021-04-10 22:59:07 +0200
committerstuebinm2021-04-10 22:59:07 +0200
commit2958333c83dce911463734e391fe3ccc76cfc9d5 (patch)
treef8b6a6370222f6f1053061f684c27ead563b7c74 /dhall
parentc307b914eca192f8e8648345e365f9c0207bc18c (diff)
add type substitutions to serde_dhall
this adds subsititutions, which work similar to the `Dhall.substitutions` mechanism of the Haskell dhall package, and which can be used e.g. like this: ```rust serde_dhall.from_str(...) .substitute_names(hashmap!["Newtype" => static_type]) .parse::<SimpleType>()? ``` The idea behind this is to make it easy to add programmer-defined types which may be used in configs for programs, without forcing the program's users to re-import the same type definitions each time (or the programmers to keep the dhall-based definitions in sync with their rust types, since these are now generated automatically). Caveats so far: - makes some of the code ugly (dhall internals are now used in serde_dhall/src/lib.rs, for example) - haven't tested error messages so far - some unecessary copying of strings and static type values
Diffstat (limited to '')
-rw-r--r--dhall/src/lib.rs5
-rw-r--r--dhall/src/syntax/ast/expr.rs13
2 files changed, 18 insertions, 0 deletions
diff --git a/dhall/src/lib.rs b/dhall/src/lib.rs
index 4238b6e..f3a11a1 100644
--- a/dhall/src/lib.rs
+++ b/dhall/src/lib.rs
@@ -99,6 +99,11 @@ impl Parsed {
pub fn to_expr(&self) -> Expr {
self.0.clone()
}
+
+ pub fn substitute_name(self, label: syntax::Label, value: Expr) -> Parsed {
+ let Parsed (expr, import_location) = self;
+ Parsed (expr.substitute_name(label, value), import_location)
+ }
}
impl<'cx> Resolved<'cx> {
diff --git a/dhall/src/syntax/ast/expr.rs b/dhall/src/syntax/ast/expr.rs
index eba2735..bc3ffa4 100644
--- a/dhall/src/syntax/ast/expr.rs
+++ b/dhall/src/syntax/ast/expr.rs
@@ -182,6 +182,19 @@ impl Expr {
let data = binary::encode(self)?;
Ok(crate::utils::sha256_hash(&data))
}
+
+ /// this wraps the expression into an additional let-binding
+ pub fn substitute_name(self, label: Label, value: Expr) -> Expr {
+ Expr::new(
+ ExprKind::Let(
+ label,
+ None,
+ value,
+ self
+ ),
+ Span::Artificial
+ )
+ }
}
// Empty enum to indicate that no error can occur