From 1f3fb40bccba6d01bd55a09c82efa5e98fbd8fc7 Mon Sep 17 00:00:00 2001
From: Brummel <mould@mycelium.de>
Date: Sun, 29 Mar 2026 18:59:38 +0200
Subject: [PATCH] Update record type computation

This commit refactors the way record types are computed within the
optimizer. Previously, the optimizer would often reuse the existing
`NodeMetrics` for records, which could lead to stale or polymorphic
types.

The changes introduce a new function, `compute_record_type`, which
explicitly recalculates the `StaticType` for a `Record` node based on
the concrete types of its child fields. This ensures that after
optimizations like inlining and folding, record types are as concrete as
possible, eliminating unresolved `TypeVars`.

Additionally, the `folder.rs` module is updated to recompute the
`RecordLayout` when creating constant record values, further improving
type accuracy. Two new tests are added to verify that inlined records,
including those with multiple fields, correctly result in concrete
types.
---
 src/ast/compiler/optimizer/engine.rs | 23 +++++++++++++++++--
 src/ast/compiler/optimizer/folder.rs | 11 +++++++++-
 tests/optimizer.rs                   | 33 ++++++++++++++++++++++++++++
 3 files changed, 64 insertions(+), 3 deletions(-)

diff --git a/src/ast/compiler/optimizer/engine.rs b/src/ast/compiler/optimizer/engine.rs
index f81ce08..7eb05b6 100644
--- a/src/ast/compiler/optimizer/engine.rs
+++ b/src/ast/compiler/optimizer/engine.rs
@@ -2,7 +2,8 @@ use crate::ast::nodes::{
     Address, AnalyzedNode, AssignBinding, GlobalAnalyzedRegistry,
     IdentifierBinding, LambdaBinding, Node, NodeKind, NodeMetrics, UpvalueIdx, VirtualId,
 };
-use crate::ast::types::{Purity, Signature, StaticType, Value};
+use crate::ast::types::{Purity, RecordLayout, Signature, StaticType, Value};
+use std::sync::Arc;
 use crate::ast::vm::GlobalStore;
 
 use std::cell::RefCell;
@@ -39,6 +40,23 @@ fn compute_tuple_type(elements: &[Rc<AnalyzedNode>]) -> StaticType {
     }
 }
 
+/// Recompute the `StaticType` for a Record node from its children's concrete types.
+/// Mirrors the type-computation logic in `TypeChecker::check_node` for `NodeKind::Record`.
+fn compute_record_type(
+    layout: &Arc<RecordLayout>,
+    fields: &[(Rc<AnalyzedNode>, Rc<AnalyzedNode>)],
+) -> StaticType {
+    let new_fields: Vec<_> = layout
+        .fields
+        .iter()
+        .zip(fields.iter())
+        .map(|((keyword, _old_ty), (_key_node, val_node))| {
+            (*keyword, val_node.ty.original.ty.clone())
+        })
+        .collect();
+    StaticType::Record(RecordLayout::get_or_create(new_fields))
+}
+
 /// Return `NodeMetrics` with an updated `StaticType` if it differs from the
 /// original, otherwise clone cheaply. Avoids unnecessary `Rc` allocations.
 fn refreshed_metrics(old: &NodeMetrics, new_ty: StaticType) -> NodeMetrics {
@@ -745,12 +763,13 @@ impl Optimizer {
                     return node_rc;
                 }
 
+                let metrics = refreshed_metrics(&node.ty, compute_record_type(layout, &mapped_fields));
                 (
                     NodeKind::Record {
                         fields: mapped_fields,
                         layout: layout.clone(),
                     },
-                    node.ty.clone(),
+                    metrics,
                 )
             }
             NodeKind::Expansion {
diff --git a/src/ast/compiler/optimizer/folder.rs b/src/ast/compiler/optimizer/folder.rs
index f1296cd..5f632a7 100644
--- a/src/ast/compiler/optimizer/folder.rs
+++ b/src/ast/compiler/optimizer/folder.rs
@@ -69,7 +69,16 @@ impl<'a> Folder<'a> {
             }
         }
 
-        let record_val = Value::Record(layout.clone(), Rc::new(constant_values));
+        // Recompute layout from concrete value types to eliminate stale TypeVars.
+        let new_fields: Vec<_> = layout
+            .fields
+            .iter()
+            .zip(values.iter())
+            .map(|((keyword, _), v_node)| (*keyword, v_node.ty.original.ty.clone()))
+            .collect();
+        let new_layout = RecordLayout::get_or_create(new_fields);
+
+        let record_val = Value::Record(new_layout, Rc::new(constant_values));
         Some(self.make_constant_node(record_val, template))
     }
 
diff --git a/tests/optimizer.rs b/tests/optimizer.rs
index cd46707..a1dbeb9 100644
--- a/tests/optimizer.rs
+++ b/tests/optimizer.rs
@@ -277,3 +277,36 @@ fn test_block_and_lambda_propagate_concrete_type_after_inlining() {
         "Block type must be concrete. Line:\n{block_line}"
     );
 }
+
+// ── Record type recomputation after inlining ────────────────────────────────
+
+#[test]
+fn test_inlined_record_has_concrete_type() {
+    // A polymorphic function returning a record, called with a concrete arg.
+    // After inlining + folding, the record type must be concrete (no TypeVars).
+    let env = Environment::new();
+    let source = r#"(do
+        (def wrap (fn [x] {:val x}))
+        (wrap 42)
+    )"#;
+    let dump = env.dump_ast_compact(source).unwrap();
+    assert!(
+        !dump.contains('?'),
+        "Inlined record must not contain unresolved TypeVars. Dump:\n{dump}"
+    );
+}
+
+#[test]
+fn test_inlined_record_has_concrete_type_multi_field() {
+    // Heterogeneous case: Int + String fields should produce concrete record type.
+    let env = Environment::new();
+    let source = r#"(do
+        (def mkr (fn [a b] {:x a :y b}))
+        (mkr 1 "hello")
+    )"#;
+    let dump = env.dump_ast_compact(source).unwrap();
+    assert!(
+        !dump.contains('?'),
+        "Inlined multi-field record must not contain unresolved TypeVars. Dump:\n{dump}"
+    );
+}