Implement typechecking of toMap

11 files changed, 134 insertions, 26 deletions

diff --git a/dhall/build.rs b/dhall/build.rs
index 9cc07ea..5523ef3 100644
--- a/dhall/build.rs
+++ b/dhall/build.rs
@@ -313,11 +313,6 @@ fn generate_tests() -> std::io::Result<()> {
                     || path == "unit/RecordProjectionByType"
                     || path == "unit/RecordProjectionByTypeEmpty"
                     || path == "unit/RecordProjectionByTypeJudgmentalEquality"
-                    // TODO: toMap
-                    || path == "unit/ToMap"
-                    || path == "unit/ToMapAnnotated"
-                    || path == "unit/ToMapInferTypeFromRecord"
-                    || path == "simple/toMapEmptyNormalizeAnnotation"
                     // TODO: record completion
                     || path == "simple/completion"
                     || path == "unit/Completion"
@@ -334,16 +329,6 @@ fn generate_tests() -> std::io::Result<()> {
                     // TODO: projection by expression
                     || path == "unit/RecordProjectionByTypeFieldTypeMismatch"
                     || path == "unit/RecordProjectionByTypeNotPresent"
-                    // TODO: toMap
-                    || path == "unit/EmptyToMap"
-                    || path == "unit/HeterogenousToMap"
-                    || path == "unit/MistypedToMap1"
-                    || path == "unit/MistypedToMap2"
-                    || path == "unit/MistypedToMap3"
-                    || path == "unit/MistypedToMap4"
-                    || path == "unit/NonRecordToMap"
-                    || path == "unit/ToMapEmptyInvalidAnnotation"
-                    || path == "unit/ToMapWrongKind"
                     // TODO: record completion
                     || path == "unit/CompletionMissingRequiredField"
                     || path == "unit/CompletionWithWrongDefaultType"
@@ -364,16 +349,6 @@ fn generate_tests() -> std::io::Result<()> {
                     // TODO: projection by expression
                     || path == "unit/RecordProjectionByTypeFieldTypeMismatch"
                     || path == "unit/RecordProjectionByTypeNotPresent"
-                    // TODO: toMap
-                    || path == "unit/EmptyToMap"
-                    || path == "unit/HeterogenousToMap"
-                    || path == "unit/MistypedToMap1"
-                    || path == "unit/MistypedToMap2"
-                    || path == "unit/MistypedToMap3"
-                    || path == "unit/MistypedToMap4"
-                    || path == "unit/NonRecordToMap"
-                    || path == "unit/ToMapEmptyInvalidAnnotation"
-                    || path == "unit/ToMapWrongKind"
                     // TODO: record completion
                     || path == "unit/CompletionMissingRequiredField"
                     || path == "unit/CompletionWithWrongDefaultType"
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() {
diff --git a/dhall/tests/type-errors/unit/EmptyToMap.txt b/dhall/tests/type-errors/unit/EmptyToMap.txt
new file mode 100644
index 0000000..000fac7
--- /dev/null
+++ b/dhall/tests/type-errors/unit/EmptyToMap.txt
@@ -0,0 +1,6 @@
+Type error: error: `toMap` applied to an empty record requires a type annotation
+ --> <current file>:1:0
+  |
+1 | toMap {=}
+  | ^^^^^^^^^ `toMap` applied to an empty record requires a type annotation
+  |
diff --git a/dhall/tests/type-errors/unit/HeterogenousToMap.txt b/dhall/tests/type-errors/unit/HeterogenousToMap.txt
new file mode 100644
index 0000000..2f8abf2
--- /dev/null
+++ b/dhall/tests/type-errors/unit/HeterogenousToMap.txt
@@ -0,0 +1,6 @@
+Type error: error: Every field of the record must have the same type
+ --> <current file>:1:0
+  |
+1 | toMap { foo= 1, bar= "Bar" }
+  | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^ Every field of the record must have the same type
+  |
diff --git a/dhall/tests/type-errors/unit/MistypedToMap1.txt b/dhall/tests/type-errors/unit/MistypedToMap1.txt
new file mode 100644
index 0000000..14d9791
--- /dev/null
+++ b/dhall/tests/type-errors/unit/MistypedToMap1.txt
@@ -0,0 +1,6 @@
+Type error: error: Annotation mismatch
+ --> <current file>:1:0
+  |
+1 | toMap { foo= 1, bar= 4 } : Natural
+  | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ Annotation mismatch
+  |
diff --git a/dhall/tests/type-errors/unit/MistypedToMap2.txt b/dhall/tests/type-errors/unit/MistypedToMap2.txt
new file mode 100644
index 0000000..88e303e
--- /dev/null
+++ b/dhall/tests/type-errors/unit/MistypedToMap2.txt
@@ -0,0 +1,6 @@
+Type error: error: Annotation mismatch
+ --> <current file>:1:0
+  |
+1 | toMap { foo= 1, bar= 4 } : List Natural
+  | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ Annotation mismatch
+  |
diff --git a/dhall/tests/type-errors/unit/MistypedToMap3.txt b/dhall/tests/type-errors/unit/MistypedToMap3.txt
new file mode 100644
index 0000000..6b3772d
--- /dev/null
+++ b/dhall/tests/type-errors/unit/MistypedToMap3.txt
@@ -0,0 +1,6 @@
+Type error: error: Annotation mismatch
+ --> <current file>:1:0
+  |
+1 | toMap { foo= 1, bar= 4 } : List { mapKey : Natural, mapValue : Natural }
+  | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ Annotation mismatch
+  |
diff --git a/dhall/tests/type-errors/unit/MistypedToMap4.txt b/dhall/tests/type-errors/unit/MistypedToMap4.txt
new file mode 100644
index 0000000..e0cf651
--- /dev/null
+++ b/dhall/tests/type-errors/unit/MistypedToMap4.txt
@@ -0,0 +1,6 @@
+Type error: error: Annotation mismatch
+ --> <current file>:1:0
+  |
+1 | toMap { foo= 1, bar= 4 } : List { mapKey : Text, mapValue : Text }
+  | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ Annotation mismatch
+  |
diff --git a/dhall/tests/type-errors/unit/NonRecordToMap.txt b/dhall/tests/type-errors/unit/NonRecordToMap.txt
new file mode 100644
index 0000000..8e83002
--- /dev/null
+++ b/dhall/tests/type-errors/unit/NonRecordToMap.txt
@@ -0,0 +1,6 @@
+Type error: error: The argument to `toMap` must be a record
+ --> <current file>:1:0
+  |
+1 | toMap "text"
+  | ^^^^^^^^^^^^ The argument to `toMap` must be a record
+  |
diff --git a/dhall/tests/type-errors/unit/ToMapEmptyInvalidAnnotation.txt b/dhall/tests/type-errors/unit/ToMapEmptyInvalidAnnotation.txt
new file mode 100644
index 0000000..c28073e
--- /dev/null
+++ b/dhall/tests/type-errors/unit/ToMapEmptyInvalidAnnotation.txt
@@ -0,0 +1,7 @@
+Type error: error: The type of `toMap x` must be of the form `List { mapKey : Text, mapValue : T }`
+ --> <current file>:2:0
+  |
+1 | -- The mapKey must be Text
+2 | toMap {=} : List { mapKey : Bool, mapValue : Text }
+  | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ The type of `toMap x` must be of the form `List { mapKey : Text, mapValue : T }`
+  |
diff --git a/dhall/tests/type-errors/unit/ToMapWrongKind.txt b/dhall/tests/type-errors/unit/ToMapWrongKind.txt
new file mode 100644
index 0000000..8158c08
--- /dev/null
+++ b/dhall/tests/type-errors/unit/ToMapWrongKind.txt
@@ -0,0 +1,6 @@
+Type error: error: `toMap` only accepts records of type `Type`
+ --> <current file>:1:0
+  |
+1 | toMap { x = Bool }
+  | ^^^^^^^^^^^^^^^^^^ `toMap` only accepts records of type `Type`
+  |