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-rw-r--r--dhall/src/error/mod.rs2
-rw-r--r--dhall/src/phase/normalize.rs2
-rw-r--r--dhall/src/phase/typecheck.rs52
3 files changed, 50 insertions, 6 deletions
diff --git a/dhall/src/error/mod.rs b/dhall/src/error/mod.rs
index 2f65443..aef84a9 100644
--- a/dhall/src/error/mod.rs
+++ b/dhall/src/error/mod.rs
@@ -77,9 +77,11 @@ pub(crate) enum TypeMessage {
MergeAnnotMismatch,
MergeHandlerTypeMismatch,
MergeHandlerReturnTypeMustNotBeDependent,
+ MustCombineRecord(Typed),
ProjectionMustBeRecord,
ProjectionMissingEntry,
Sort,
+ RecordMismatch(Typed, Typed),
RecordTypeDuplicateField,
RecordTypeMergeRequiresRecordType(Type),
RecordTypeMismatch(Type, Type, Type, Type),
diff --git a/dhall/src/phase/normalize.rs b/dhall/src/phase/normalize.rs
index 653f415..4a25ed9 100644
--- a/dhall/src/phase/normalize.rs
+++ b/dhall/src/phase/normalize.rs
@@ -404,7 +404,7 @@ where
kvs
}
-fn merge_maps<K, V>(
+pub(crate) fn merge_maps<K, V>(
map1: &HashMap<K, V>,
map2: &HashMap<K, V>,
mut f: impl FnMut(&V, &V) -> V,
diff --git a/dhall/src/phase/typecheck.rs b/dhall/src/phase/typecheck.rs
index bd8e1bb..3bff7ca 100644
--- a/dhall/src/phase/typecheck.rs
+++ b/dhall/src/phase/typecheck.rs
@@ -598,6 +598,47 @@ fn type_last_layer(
}
Ok(RetTypeOnly(text_type))
}
+ BinOp(RightBiasedRecordMerge, l, r) => {
+ use crate::phase::normalize::merge_maps;
+
+ let l_type = l.get_type()?;
+ let l_kind = l_type.get_type()?;
+ let r_type = r.get_type()?;
+ let r_kind = r_type.get_type()?;
+
+ // Check the equality of kinds.
+ // This is to disallow expression such as:
+ // "{ x = Text } // { y = 1 }"
+ ensure_equal!(
+ l_kind,
+ r_kind,
+ mkerr(RecordMismatch(l.clone(), r.clone())),
+ );
+
+ // Extract the LHS record type
+ let kts_x = match l_type.to_value() {
+ Value::RecordType(kts) => kts,
+ _ => return Err(mkerr(MustCombineRecord(l.clone()))),
+ };
+
+ // Extract the RHS record type
+ let kts_y = match r_type.to_value() {
+ Value::RecordType(kts) => kts,
+ _ => return Err(mkerr(MustCombineRecord(r.clone()))),
+ };
+
+ // Union the two records, prefering
+ // the values found in the RHS.
+ let kts = merge_maps(&kts_x, &kts_y, |_, r_t| r_t.clone());
+
+ // Construct the final record type from the union
+ Ok(RetTypeOnly(tck_record_type(
+ ctx,
+ kts.iter()
+ .map(|(x, v)| Ok((x.clone(), v.to_type()))),
+ )?
+ .into_type()))
+ }
BinOp(RecursiveRecordTypeMerge, l, r) => {
// A recursive function to dig down into
// records of records when merging.
@@ -699,6 +740,7 @@ fn type_last_layer(
NaturalTimes => Natural,
TextAppend => Text,
ListAppend => unreachable!(),
+ RightBiasedRecordMerge => unreachable!(),
RecursiveRecordTypeMerge => unreachable!(),
_ => return Err(mkerr(Unimplemented)),
})?;
@@ -1213,11 +1255,11 @@ mod spec_tests {
ti_success!(ti_success_unit_RecursiveRecordTypeMergeTwo, "unit/RecursiveRecordTypeMergeTwo");
ti_success!(ti_success_unit_RecursiveRecordTypeMergeTwoKinds, "unit/RecursiveRecordTypeMergeTwoKinds");
ti_success!(ti_success_unit_RecursiveRecordTypeMergeTwoTypes, "unit/RecursiveRecordTypeMergeTwoTypes");
- // ti_success!(ti_success_unit_RightBiasedRecordMergeRhsEmpty, "unit/RightBiasedRecordMergeRhsEmpty");
- // ti_success!(ti_success_unit_RightBiasedRecordMergeTwo, "unit/RightBiasedRecordMergeTwo");
- // ti_success!(ti_success_unit_RightBiasedRecordMergeTwoDifferent, "unit/RightBiasedRecordMergeTwoDifferent");
- // ti_success!(ti_success_unit_RightBiasedRecordMergeTwoKinds, "unit/RightBiasedRecordMergeTwoKinds");
- // ti_success!(ti_success_unit_RightBiasedRecordMergeTwoTypes, "unit/RightBiasedRecordMergeTwoTypes");
+ ti_success!(ti_success_unit_RightBiasedRecordMergeRhsEmpty, "unit/RightBiasedRecordMergeRhsEmpty");
+ ti_success!(ti_success_unit_RightBiasedRecordMergeTwo, "unit/RightBiasedRecordMergeTwo");
+ ti_success!(ti_success_unit_RightBiasedRecordMergeTwoDifferent, "unit/RightBiasedRecordMergeTwoDifferent");
+ ti_success!(ti_success_unit_RightBiasedRecordMergeTwoKinds, "unit/RightBiasedRecordMergeTwoKinds");
+ ti_success!(ti_success_unit_RightBiasedRecordMergeTwoTypes, "unit/RightBiasedRecordMergeTwoTypes");
ti_success!(ti_success_unit_SomeTrue, "unit/SomeTrue");
ti_success!(ti_success_unit_Text, "unit/Text");
ti_success!(ti_success_unit_TextLiteral, "unit/TextLiteral");