Merge pull request #193 from basile-henry/with-no-desugar

3 files changed, 103 insertions, 33 deletions

diff --git a/dhall/src/operations/normalization.rs b/dhall/src/operations/normalization.rs
index b930f93..dbd58f9 100644
--- a/dhall/src/operations/normalization.rs
+++ b/dhall/src/operations/normalization.rs
@@ -4,7 +4,7 @@ use std::iter::once;
 
 use crate::operations::{BinOp, OpKind};
 use crate::semantics::{
-    merge_maps, ret_kind, ret_op, ret_ref, Nir, NirKind, Ret, TextLit,
+    merge_maps, ret_kind, ret_nir, ret_op, ret_ref, Nir, NirKind, Ret, TextLit,
 };
 use crate::syntax::{ExprKind, Label, NumKind};
 
@@ -299,7 +299,64 @@ pub fn normalize_operation(opkind: &OpKind<Nir>) -> Ret {
             )),
             _ => nothing_to_do(),
         },
-        Completion(..) | With(..) => {
+        With(record, labels, expr) => {
+            let mut current_nir: Option<Nir> = Some(record.clone());
+            let mut visited: Vec<(&Label, HashMap<Label, Nir>)> = Vec::new();
+            let mut to_create = Vec::new();
+
+            // To be used when an abstract entry is reached
+            let mut abstract_nir = None;
+
+            for label in labels {
+                match current_nir {
+                    None => to_create.push(label.clone()),
+                    Some(nir) => match nir.kind() {
+                        RecordLit(kvs) => {
+                            current_nir = kvs.get(label).cloned();
+                            visited.push((label, kvs.clone()));
+                        }
+                        // Handle partially abstract case
+                        _ => {
+                            abstract_nir = Some(nir);
+                            to_create.push(label.clone());
+                            current_nir = None;
+                        }
+                    },
+                }
+            }
+
+            // Create Nir for record bottom up
+            let mut nir = expr.clone();
+
+            match abstract_nir {
+                // No abstract nir, creating singleton records
+                None => {
+                    while let Some(label) = to_create.pop() {
+                        let rec =
+                            RecordLit(once((label.clone(), nir)).collect());
+                        nir = Nir::from_kind(rec);
+                    }
+                }
+                // Abstract nir, creating with op
+                Some(abstract_nir) => {
+                    nir = Nir::from_kind(Op(OpKind::With(
+                        abstract_nir,
+                        to_create,
+                        nir,
+                    )));
+                }
+            }
+
+            // Update visited records
+            while let Some((label, mut kvs)) = visited.pop() {
+                kvs.insert(label.clone(), nir);
+                let rec = RecordLit(kvs);
+                nir = Nir::from_kind(rec);
+            }
+
+            ret_nir(nir)
+        }
+        Completion(..) => {
             unreachable!("This case should have been handled in resolution")
         }
     }
diff --git a/dhall/src/operations/typecheck.rs b/dhall/src/operations/typecheck.rs
index 2ccc17d..9329aff 100644
--- a/dhall/src/operations/typecheck.rs
+++ b/dhall/src/operations/typecheck.rs
@@ -503,7 +503,48 @@ pub fn typecheck_operation(
 
             selection_val
         }
-        Completion(..) | With(..) => {
+        With(record, labels, expr) => {
+            use crate::syntax::Label;
+            use std::iter::once;
+
+            let mut current_nir: Option<Nir> =
+                Some(record.ty().as_nir().clone());
+            let mut visited: Vec<(&Label, HashMap<Label, Nir>)> = Vec::new();
+            let mut to_create = Vec::new();
+
+            for label in labels {
+                match current_nir {
+                    None => to_create.push(label),
+                    Some(nir) => {
+                        let kts = (match nir.kind() {
+                            NirKind::RecordType(kts) => Ok(kts.clone()),
+                            _ => mk_span_err(span.clone(), "WithMustBeRecord"), // TODO better error
+                        })?;
+
+                        current_nir = kts.get(label).cloned();
+                        visited.push((label, kts));
+                    }
+                }
+            }
+
+            // Create Nir for record type bottom up
+            let mut nir = expr.ty().as_nir().clone();
+
+            while let Some(label) = to_create.pop() {
+                let rec = RecordType(once((label.clone(), nir)).collect());
+                nir = Nir::from_kind(rec);
+            }
+
+            // Update visited records
+            while let Some((label, mut kts)) = visited.pop() {
+                kts.insert(label.clone(), nir);
+                let rec = RecordType(kts);
+                nir = Nir::from_kind(rec);
+            }
+
+            Type::new_infer_universe(env, nir)?
+        }
+        Completion(..) => {
             unreachable!("This case should have been handled in resolution")
         }
     })
diff --git a/dhall/src/semantics/resolve/resolve.rs b/dhall/src/semantics/resolve/resolve.rs
index 572df25..dc1951e 100644
--- a/dhall/src/semantics/resolve/resolve.rs
+++ b/dhall/src/semantics/resolve/resolve.rs
@@ -2,7 +2,6 @@ use itertools::Itertools;
 use std::borrow::Cow;
 use std::collections::BTreeMap;
 use std::env;
-use std::iter::once;
 use std::path::PathBuf;
 use url::Url;
 
@@ -13,8 +12,8 @@ use crate::operations::{BinOp, OpKind};
 use crate::semantics::{mkerr, Hir, HirKind, ImportEnv, NameEnv, Type};
 use crate::syntax;
 use crate::syntax::{
-    Expr, ExprKind, FilePath, FilePrefix, Hash, ImportMode, ImportTarget,
-    Label, Span, UnspannedExpr, URL,
+    Expr, ExprKind, FilePath, FilePrefix, Hash, ImportMode, ImportTarget, Span,
+    UnspannedExpr, URL,
 };
 use crate::{Parsed, Resolved, Typed};
 
@@ -267,30 +266,6 @@ fn resolve_one_import(
     Ok(Typed { hir, ty })
 }
 
-/// Desugar a `with` expression.
-fn desugar_with(x: Expr, path: &[Label], y: Expr, span: Span) -> Expr {
-    use crate::operations::BinOp::RightBiasedRecordMerge;
-    use ExprKind::{Op, RecordLit};
-    use OpKind::{BinOp, Field};
-    let expr = |k| Expr::new(k, span.clone());
-    match path {
-        [] => y,
-        [l, rest @ ..] => {
-            let res = desugar_with(
-                expr(Op(Field(x.clone(), l.clone()))),
-                rest,
-                y,
-                span.clone(),
-            );
-            expr(Op(BinOp(
-                RightBiasedRecordMerge,
-                x,
-                expr(RecordLit(once((l.clone(), res)).collect())),
-            )))
-        }
-    }
-}
-
 /// Desugar the first level of the expression.
 fn desugar(expr: &Expr) -> Cow<'_, Expr> {
     match expr.kind() {
@@ -316,9 +291,6 @@ fn desugar(expr: &Expr) -> Cow<'_, Expr> {
                 expr.span(),
             ))
         }
-        ExprKind::Op(OpKind::With(x, path, y)) => {
-            Cow::Owned(desugar_with(x.clone(), path, y.clone(), expr.span()))
-        }
         _ => Cow::Borrowed(expr),
     }
 }