Fix bug that caused generics to resolve an ancestral version (#40)

In terms of inheritance

src/__tests__/compiler.test.ts

@@ -40,6 +40,8 @@ describe("E2E Compiler Pipeline", () => {
     const test7 = getWasmFn("test7", instance);
     const test8 = getWasmFn("test8", instance);
     const test9 = getWasmFn("test9", instance);
+    const test10 = getWasmFn("test10", instance);
+    const test11 = getWasmFn("test11", instance);
     assert(test1, "Test1 exists");
     assert(test2, "Test2 exists");
     assert(test3, "Test3 exists");
@@ -49,6 +51,8 @@ describe("E2E Compiler Pipeline", () => {
     assert(test7, "Test7 exists");
     assert(test8, "Test8 exists");
     assert(test9, "Test9 exists");
+    assert(test10, "Test10 exists");
+    assert(test11, "Test11 exists");
 
     // Static method resolution tests
     t.expect(test1(), "test 1 returns correct value").toEqual(13);
@@ -66,6 +70,8 @@ describe("E2E Compiler Pipeline", () => {
 
     // Generic object type test
     t.expect(test9(), "test 9 returns correct value").toEqual(7.5);
+    t.expect(test10(), "test 10 returns correct value").toEqual(12);
+    t.expect(test11(), "test 11 returns correct value").toEqual(4);
   });
 
   test("Compiler can do tco", async (t) => {

src/__tests__/fixtures/e2e-file.ts

@@ -116,6 +116,37 @@ pub fn test9()
 
   let vec2 = VecGeneric<f64> { x: 7.5, y: 2.5, z: 3.5 }
   vec2.x
+
+// Test generic object inheritance strictness
+fn generic_get_member<T>(vec: T)
+  vec.get_member()
+
+// Ensure generic instances of an ancestor aren't used in place of a descendant, should return 12
+pub fn test10()
+  let vec = Vec { x: 7, y: 2}
+  generic_get_member<Vec>(vec)
+
+  let point = Point { x: 12, y: 17, z: 4 }
+  generic_get_member<Point>(point)
+
+  let pointy = Pointy { x: 12, y: 17, z: 4 }
+  generic_get_member<Pointy>(pointy)
+
+// Test generic object inheritance strictness
+obj VecBox<T> {
+  box: T
+}
+
+obj PointF extends Vec {
+  x: i32,
+  y: i32,
+  f: i32
+}
+
+pub fn test11()
+  let pf = PointF { x: 12, y: 17, f: 4 }
+  let pf_box = VecBox<PointF> { box: pf }
+  pf_box.box.f
 `;
 
 export const tcoText = `

src/semantics/check-types.ts

@@ -76,7 +76,7 @@ const checkObjectInit = (call: Call): Call => {
   checkTypes(literal);
 
   // Check to ensure literal structure is compatible with nominal structure
-  if (!typesAreEquivalent(literal.type, call.type, true)) {
+  if (!typesAreEquivalent(literal.type, call.type, { structuralOnly: true })) {
     throw new Error(`Object literal type does not match expected type`);
   }
 

src/semantics/resolution/get-call-fn.ts

@@ -61,7 +61,9 @@ const typeArgsMatch = (call: Call, candidate: Fn): boolean =>
     ? candidate.appliedTypeArgs.every((t, i) => {
         const argType = getExprType(call.typeArgs?.at(i));
         const appliedType = getExprType(t);
-        return typesAreEquivalent(argType, appliedType);
+        return typesAreEquivalent(argType, appliedType, {
+          exactNominalMatch: true,
+        });
       })
     : true;
 

src/semantics/resolution/resolve-object-type.ts

@@ -83,6 +83,8 @@ const typeArgsMatch = (call: Call, candidate: ObjectType): boolean =>
     ? candidate.appliedTypeArgs.every((t, i) => {
         const argType = getExprType(call.typeArgs?.at(i));
         const appliedType = getExprType(t);
-        return typesAreEquivalent(argType, appliedType);
+        return typesAreEquivalent(argType, appliedType, {
+          exactNominalMatch: true,
+        });
       })
     : true;

src/semantics/resolution/types-are-equivalent.ts

@@ -3,7 +3,13 @@ import { Type } from "../../syntax-objects/index.js";
 export const typesAreEquivalent = (
   a?: Type,
   b?: Type,
-  ignoreExtension?: boolean // Hacky
+  opts: {
+    /** Will not check that a is an extension of b if true */
+    structuralOnly?: boolean;
+
+    /** Will ancestors, the type must be the same regardless of inheritance  */
+    exactNominalMatch?: boolean;
+  } = {}
 ): boolean => {
   if (!a || !b) return false;
 
@@ -12,8 +18,10 @@ export const typesAreEquivalent = (
   }
 
   if (a.isObjectType() && b.isObjectType()) {
+    if (opts.exactNominalMatch) return a.id === b.id;
+
     return (
-      (ignoreExtension || a.extends(b)) &&
+      (opts.structuralOnly || a.extends(b)) &&
       b.fields.every((field) => {
         const match = a.fields.find((f) => f.name === field.name);
         return match && typesAreEquivalent(field.type, match.type);