diff --git a/src/ast/operand.ts b/src/ast/operand.ts
index 3e5e0a5c..b1fe44fb 100644
--- a/src/ast/operand.ts
+++ b/src/ast/operand.ts
@@ -1,6 +1,7 @@
 import { LexerToken } from '../lexer/lexer'
 import { ParseNode, ParseTree, filterNonAstNodes } from '../parser'
 import { nameLikeTokens } from '../parser/fns'
+import { InstanceRelation } from '../scope/trait'
 import { VirtualIdentifierMatch } from '../scope/vid'
 import { Typed } from '../semantic'
 import { Expr, buildExpr } from './expr'
@@ -9,7 +10,7 @@ import { MatchExpr, Pattern, buildMatchExpr, buildNumber, buildPattern } from '.
 import { Block, buildBlock } from './statement'
 import { Type, buildType } from './type'
 
-export type Operand =
+export type Operand = (
     | IfExpr
     | IfLetExpr
     | WhileExpr
@@ -24,6 +25,7 @@ export type Operand =
     | FloatLiteral
     | BoolLiteral
     | Identifier
+) & { traits?: Map<string, InstanceRelation> }
 
 export const buildOperand = (node: ParseNode): Operand => {
     const n = filterNonAstNodes(node)[0]
diff --git a/src/codegen/js/expr.ts b/src/codegen/js/expr.ts
index bc6a6686..1a537ad6 100644
--- a/src/codegen/js/expr.ts
+++ b/src/codegen/js/expr.ts
@@ -38,7 +38,14 @@ export const emitUnaryExpr = (unaryExpr: UnaryExpr, module: Module, ctx: Context
     const resultVar = nextVariable(ctx)
     switch (unaryExpr.op.kind) {
         case 'call-op':
-            const args = unaryExpr.op.args.map(a => emitExpr(a.expr, module, ctx))
+            const args = unaryExpr.op.args.map(a => {
+                const { emit, resultVar: res } = emitExpr(a.expr, module, ctx)
+                const traits = a.expr.kind === 'operand-expr' ? a.expr.operand.traits : undefined
+                const traitEmit = traits
+                    ? [...traits.entries()].map(([name, rel]) => `${a}.${name} = ${jsRelName(rel)}`)
+                    : ''
+                return { emit: emitLines([emit, ...traitEmit]), resultVar: res }
+            })
             const genericTypes = unaryExpr.op.generics?.map(g => emitGeneric(g, module, ctx)) ?? []
             const jsArgs = [...args, ...genericTypes]
             const variantDef = unaryExpr.op.variantDef
@@ -89,14 +96,19 @@ export const emitBinaryExpr = (binaryExpr: BinaryExpr, module: Module, ctx: Cont
                         ? jsArgs.map(a => a.resultVar)
                         : [lOp.resultVar, ...jsArgs.map(a => a.resultVar)]
                 ).join(', ')
+                const upcastRels = binaryExpr.lOperand.traits
+                const upcastEmit = upcastRels
+                    ? [...upcastRels.entries()].map(([name, rel]) => `${lOp.resultVar}.${name} = ${jsRelName(rel)}`)
+                    : ''
                 return {
                     emit: emitLines([
                         lOp.emit,
+                        ...upcastEmit,
                         emitLines(jsArgs.map(a => a.emit)),
                         jsVariable(
                             resultVar,
                             `${
-                                call.impl ? jsRelName(call.impl) : jsError('dynamic dispatch')
+                                call.impl ? jsRelName(call.impl) : `${lOp.resultVar}.${relTypeName(methodDef.rel)}`
                             }().${methodName}(${argsEmit})`
                         )
                     ]),
diff --git a/src/scope/trait.ts b/src/scope/trait.ts
index 748f3861..e0872fc2 100644
--- a/src/scope/trait.ts
+++ b/src/scope/trait.ts
@@ -209,7 +209,7 @@ export const relTypeName = (rel: InstanceRelation): string => {
 export const resolveGenericImpls = (generic: VirtualGeneric, ctx: Context): InstanceRelation[] => {
     return generic.bounds.flatMap(b => {
         const candidates = ctx.impls
-            .filter(i => i.instanceDef.kind === 'impl-def' && isAssignable(b, i.implType, ctx))
+            .filter(i => isAssignable(b, i.implType, ctx))
             .toSorted((a, b) => relOrdering(b) - relOrdering(a))
         return candidates.length > 0 ? [candidates.at(0)!] : []
     })
@@ -219,7 +219,10 @@ export const resolveMethodImpl = (type: VirtualType, method: MethodDef, ctx: Con
     const candidates = ctx.impls
         .filter(
             i =>
-                i.instanceDef.kind === 'impl-def' &&
+                (i.instanceDef.kind === 'impl-def' ||
+                    i.instanceDef.block.statements.find(
+                        s => s.kind === 'fn-def' && s.name.value === method.fn.name.value && s.block
+                    )) &&
                 isAssignable(type, i.forType, ctx) &&
                 isAssignable(i.implType, method.rel.implType, ctx) &&
                 (!i.inherent ||
@@ -227,11 +230,11 @@ export const resolveMethodImpl = (type: VirtualType, method: MethodDef, ctx: Con
                         s => s.kind === 'fn-def' && s.name.value === method.fn.name.value
                     ))
         )
-        .toSorted((a, b) => relOrdering(b) - relOrdering(a))
+        .toSorted((a, b) => relOrdering(b, type, method.rel.forType) - relOrdering(a, type, method.rel.forType))
     return candidates.at(0)
 }
 
-export const relOrdering = (rel: InstanceRelation): number => {
+export const relOrdering = (rel: InstanceRelation, implType?: VirtualType, forType?: VirtualType): number => {
     let score = 0
     if (rel.instanceDef.kind === 'impl-def') score += 8
     return score
diff --git a/src/util/array.ts b/src/util/array.ts
index f04ef6b7..63eeccd7 100644
--- a/src/util/array.ts
+++ b/src/util/array.ts
@@ -42,3 +42,13 @@ export const groupByHaving = <T, K>(arr: T[], keyFn: (t: T) => K, havingFn: (t:
     }
     return groups
 }
+
+export const zip = <A, B, C>(a: A[], b: B[], f: (a: A, b: B, i: number) => C): C[] => {
+    const la = a.length
+    const lb = b.length
+    const res = []
+    for (let i = 0; i < la && i < lb; i++) {
+        res.push(f(a[i], b[i], i))
+    }
+    return res
+}