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-rw-r--r--dhall/src/semantics/tck/typecheck.rs80
1 files changed, 79 insertions, 1 deletions
diff --git a/dhall/src/semantics/tck/typecheck.rs b/dhall/src/semantics/tck/typecheck.rs
index c3c589b..516ef42 100644
--- a/dhall/src/semantics/tck/typecheck.rs
+++ b/dhall/src/semantics/tck/typecheck.rs
@@ -619,7 +619,85 @@ fn type_one_layer(
(None, None) => return span_err("MergeEmptyNeedsAnnotation"),
}
}
- ExprKind::ToMap(_, _) => unimplemented!("toMap"),
+ ExprKind::ToMap(record, annot) => {
+ let record_t = record.get_type()?;
+ let kts = match record_t.kind() {
+ ValueKind::RecordType(kts) => kts,
+ _ => {
+ return span_err("The argument to `toMap` must be a record")
+ }
+ };
+
+ if kts.is_empty() {
+ let annot = if let Some(annot) = annot {
+ annot
+ } else {
+ return span_err(
+ "`toMap` applied to an empty record requires a type \
+ annotation",
+ );
+ };
+ let annot_val = annot.eval(env.as_nzenv());
+
+ let err_msg = "The type of `toMap x` must be of the form \
+ `List { mapKey : Text, mapValue : T }`";
+ let arg = match annot_val.kind() {
+ ValueKind::AppliedBuiltin(BuiltinClosure {
+ b: Builtin::List,
+ args,
+ ..
+ }) if args.len() == 1 => &args[0],
+ _ => return span_err(err_msg),
+ };
+ let kts = match arg.kind() {
+ ValueKind::RecordType(kts) => kts,
+ _ => return span_err(err_msg),
+ };
+ if kts.len() != 2 {
+ return span_err(err_msg);
+ }
+ match kts.get(&"mapKey".into()) {
+ Some(t) if *t == Value::from_builtin(Builtin::Text) => {}
+ _ => return span_err(err_msg),
+ }
+ match kts.get(&"mapValue".into()) {
+ Some(_) => {}
+ None => return span_err(err_msg),
+ }
+ annot_val
+ } else {
+ let entry_type = kts.iter().next().unwrap().1.clone();
+ if entry_type.get_type()?.as_const() != Some(Const::Type) {
+ return span_err(
+ "`toMap` only accepts records of type `Type`",
+ );
+ }
+ for (_, t) in kts.iter() {
+ if *t != entry_type {
+ return span_err(
+ "Every field of the record must have the same type",
+ );
+ }
+ }
+
+ let mut kts = HashMap::new();
+ kts.insert("mapKey".into(), Value::from_builtin(Builtin::Text));
+ kts.insert("mapValue".into(), entry_type);
+ let output_type = Value::from_builtin(Builtin::List).app(
+ Value::from_kind_and_type(
+ ValueKind::RecordType(kts),
+ Value::from_const(Const::Type),
+ ),
+ );
+ if let Some(annot) = annot {
+ let annot_val = annot.eval(env.as_nzenv());
+ if output_type != annot_val {
+ return span_err("Annotation mismatch");
+ }
+ }
+ output_type
+ }
+ }
ExprKind::Projection(record, labels) => {
let record_type = record.get_type()?;
let kts = match record_type.kind() {