Semantic: upcast for method call operand

src/semantic/instance.ts

@@ -24,6 +24,7 @@ import {
     unexpectedTypeError
 } from './error'
 import { checkExpr, checkOperand } from './expr'
+import { upcast } from './upcast'
 
 export const checkFieldAccess = (operand: Operand, name: Name, ctx: Context): VirtualType | undefined => {
     checkOperand(operand, ctx)
@@ -143,6 +144,7 @@ export const checkMethodCall = (expr: UnaryExpr, mCall: MethodCallOp, ctx: Conte
     }
     if (mCall.call.impl) {
         ctx.moduleStack.at(-1)!.relImports.push(mCall.call.impl)
+        upcast(operand, operand.type!, ref.def.rel.implType, ctx)
     }
 
     mCall.call.generics = fnType.generics.map(g => {

src/semantic/upcast.ts

@@ -11,15 +11,7 @@ export interface Upcast {
 export const upcast = (virtual: Partial<Virtual>, type: VirtualType, traitType: VirtualType, ctx: Context): void => {
     const upcastMap = makeUpcastMap(type, traitType, ctx)
     if (upcastMap) {
-        virtual.upcasts ??= new Map()
-        upcastMap.forEach((up, k) => {
-            const existing = virtual.upcasts!.get(k)
-            if (existing) {
-                up.traits.forEach((t, tk) => existing.traits.set(tk, t))
-            } else {
-                virtual.upcasts!.set(k, up)
-            }
-        })
+        writeUpcast(virtual, upcastMap)
     }
 }
 
@@ -50,3 +42,15 @@ export const makeUpcastMap = (
     ctx.moduleStack.at(-1)!.relImports.push(res.impl)
     return upcasts
 }
+
+const writeUpcast = (virtual: Partial<Virtual>, upcastMap: Map<string, Upcast>): void => {
+    virtual.upcasts ??= new Map()
+    upcastMap.forEach((up, k) => {
+        const existing = virtual.upcasts!.get(k)
+        if (existing) {
+            up.traits.forEach((t, tk) => existing.traits.set(tk, t))
+        } else {
+            virtual.upcasts!.set(k, up)
+        }
+    })
+}