diff --git a/compiler/function.go b/compiler/function.go
index 3b438a6..49afe6a 100644
--- a/compiler/function.go
+++ b/compiler/function.go
@@ -88,11 +88,25 @@ func collectFunctypes(p *packages.Package, name string, fn ast.Node, scope *func
 		if fields != nil {
 			for _, field := range fields.List {
 				for _, name := range field.Names {
+					typ := p.TypesInfo.TypeOf(name)
+					if g != nil {
+						if instanceType, ok := g.typeOfParam(typ); ok {
+							typ = instanceType
+						}
+					}
+					if typ != nil {
+						_, ellipsis := field.Type.(*ast.Ellipsis)
+						field.Type = typeExpr(p, typ)
+						if a, ok := field.Type.(*ast.ArrayType); ok && a.Len == nil && ellipsis {
+							field.Type = &ast.Ellipsis{Elt: a.Elt}
+						}
+					}
 					scope.insert(name, field.Type)
 				}
 			}
 		}
 	}
+	signature.TypeParams = nil
 
 	var inspect func(ast.Node) bool
 	inspect = func(node ast.Node) bool {
@@ -110,11 +124,17 @@ func collectFunctypes(p *packages.Package, name string, fn ast.Node, scope *func
 					switch s := spec.(type) {
 					case *ast.ValueSpec:
 						for _, name := range s.Names {
-							typ := s.Type
+							typ := p.TypesInfo.TypeOf(name)
+							if g != nil {
+								if instanceType, ok := g.typeOfParam(typ); ok {
+									typ = instanceType
+								}
+							}
 							if typ == nil {
-								typ = typeExpr(p, p.TypesInfo.TypeOf(name))
+								scope.insert(name, s.Type)
+							} else {
+								scope.insert(name, typeExpr(p, typ))
 							}
-							scope.insert(name, typ)
 						}
 					}
 				}
diff --git a/compiler/testdata/coroutine_durable.go b/compiler/testdata/coroutine_durable.go
index 941ffdc..3985528 100644
--- a/compiler/testdata/coroutine_durable.go
+++ b/compiler/testdata/coroutine_durable.go
@@ -4,15 +4,17 @@ package testdata
 
 import (
 	coroutine "github.com/stealthrocket/coroutine"
-	unsafe "unsafe"
 	time "time"
+	unsafe "unsafe"
 )
 import _types "github.com/stealthrocket/coroutine/types"
 
 func SomeFunctionThatShouldExistInTheCompiledFile() {
 }
+
 //go:noinline
 func Identity(n int) { coroutine.Yield[int, any](n) }
+
 //go:noinline
 func SquareGenerator(_fn0 int) {
 	_c := coroutine.LoadContext[int, any]()
@@ -48,6 +50,7 @@ func SquareGenerator(_fn0 int) {
 		}
 	}
 }
+
 //go:noinline
 func SquareGeneratorTwice(_fn0 int) {
 	_c := coroutine.LoadContext[int, any]()
@@ -78,6 +81,7 @@ func SquareGeneratorTwice(_fn0 int) {
 		SquareGenerator(_f0.X0)
 	}
 }
+
 //go:noinline
 func SquareGeneratorTwiceLoop(_fn0 int) {
 	_c := coroutine.LoadContext[int, any]()
@@ -113,6 +117,7 @@ func SquareGeneratorTwiceLoop(_fn0 int) {
 		}
 	}
 }
+
 //go:noinline
 func EvenSquareGenerator(_fn0 int) {
 	_c := coroutine.LoadContext[int, any]()
@@ -160,6 +165,7 @@ func EvenSquareGenerator(_fn0 int) {
 		}
 	}
 }
+
 //go:noinline
 func NestedLoops(_fn0 int) (_ int) {
 	_c := coroutine.LoadContext[int, any]()
@@ -241,6 +247,7 @@ func NestedLoops(_fn0 int) (_ int) {
 	}
 	panic("unreachable")
 }
+
 //go:noinline
 func FizzBuzzIfGenerator(_fn0 int) {
 	_c := coroutine.LoadContext[int, any]()
@@ -301,6 +308,7 @@ func FizzBuzzIfGenerator(_fn0 int) {
 		}
 	}
 }
+
 //go:noinline
 func FizzBuzzSwitchGenerator(_fn0 int) {
 	_c := coroutine.LoadContext[int, any]()
@@ -385,6 +393,7 @@ func FizzBuzzSwitchGenerator(_fn0 int) {
 		}
 	}
 }
+
 //go:noinline
 func Shadowing(_ int) {
 	_c := coroutine.LoadContext[int, any]()
@@ -727,6 +736,7 @@ func Shadowing(_ int) {
 		coroutine.Yield[int, any](_f0.X22)
 	}
 }
+
 //go:noinline
 func RangeSliceIndexGenerator(_ int) {
 	_c := coroutine.LoadContext[int, any]()
@@ -769,6 +779,7 @@ func RangeSliceIndexGenerator(_ int) {
 		}
 	}
 }
+
 //go:noinline
 func RangeArrayIndexValueGenerator(_ int) {
 	_c := coroutine.LoadContext[int, any]()
@@ -825,6 +836,7 @@ func RangeArrayIndexValueGenerator(_ int) {
 		}
 	}
 }
+
 //go:noinline
 func TypeSwitchingGenerator(_ int) {
 	_c := coroutine.LoadContext[int, any]()
@@ -899,6 +911,7 @@ func TypeSwitchingGenerator(_ int) {
 		}
 	}
 }
+
 //go:noinline
 func LoopBreakAndContinue(_ int) {
 	_c := coroutine.LoadContext[int, any]()
@@ -1053,6 +1066,7 @@ func LoopBreakAndContinue(_ int) {
 		}
 	}
 }
+
 //go:noinline
 func RangeOverMaps(_fn0 int) {
 	_c := coroutine.LoadContext[int, any]()
@@ -1387,6 +1401,7 @@ func RangeOverMaps(_fn0 int) {
 		}
 	}
 }
+
 //go:noinline
 func Range(_fn0 int, _fn1 func(int)) {
 	_c := coroutine.LoadContext[int, any]()
@@ -1425,13 +1440,15 @@ func Range(_fn0 int, _fn1 func(int)) {
 		}
 	}
 }
+
 //go:noinline
 func Double(n int) { coroutine.Yield[int, any](2 * n) }
+
 //go:noinline
 func RangeTriple(n int) {
-	Range(n, func(i int) { coroutine.Yield[int, any](3 * i) },
-	)
+	Range(n, func(i int) { coroutine.Yield[int, any](3 * i) })
 }
+
 //go:noinline
 func RangeTripleFuncValue(_fn0 int) {
 	_c := coroutine.LoadContext[int, any]()
@@ -1466,6 +1483,7 @@ func RangeTripleFuncValue(_fn0 int) {
 		Range(_f0.X0, _f0.X1)
 	}
 }
+
 //go:noinline
 func RangeReverseClosureCaptureByValue(_fn0 int) {
 	_c := coroutine.LoadContext[int, any]()
@@ -1515,6 +1533,7 @@ func RangeReverseClosureCaptureByValue(_fn0 int) {
 		}
 	}
 }
+
 //go:noinline
 func Range10ClosureCapturingValues() {
 	_c := coroutine.LoadContext[int, any]()
@@ -1621,6 +1640,7 @@ func Range10ClosureCapturingValues() {
 		}
 	}
 }
+
 //go:noinline
 func Range10ClosureCapturingPointers() {
 	_c := coroutine.LoadContext[int, any]()
@@ -1737,6 +1757,7 @@ func Range10ClosureCapturingPointers() {
 		}
 	}
 }
+
 //go:noinline
 func Range10ClosureHeterogenousCapture() {
 	_c := coroutine.LoadContext[int, any]()
@@ -1956,6 +1977,7 @@ func Range10ClosureHeterogenousCapture() {
 		}
 	}
 }
+
 //go:noinline
 func Range10Heterogenous() {
 	_c := coroutine.LoadContext[int, any]()
@@ -2067,6 +2089,7 @@ func Range10Heterogenous() {
 		}
 	}
 }
+
 //go:noinline
 func Select(_fn0 int) {
 	_c := coroutine.LoadContext[int, any]()
@@ -2361,6 +2384,7 @@ func Select(_fn0 int) {
 		}
 	}
 }
+
 //go:noinline
 func YieldingExpressionDesugaring() {
 	_c := coroutine.LoadContext[int, any]()
@@ -2783,6 +2807,7 @@ func YieldingExpressionDesugaring() {
 		}
 	}
 }
+
 //go:noinline
 func a(_fn0 int) (_ int) {
 	_c := coroutine.LoadContext[int, any]()
@@ -2814,6 +2839,7 @@ func a(_fn0 int) (_ int) {
 	}
 	panic("unreachable")
 }
+
 //go:noinline
 func b(_fn0 int) (_ int) {
 	_c := coroutine.LoadContext[int, any]()
@@ -2845,6 +2871,7 @@ func b(_fn0 int) (_ int) {
 	}
 	panic("unreachable")
 }
+
 //go:noinline
 func YieldingDurations() {
 	_c := coroutine.LoadContext[int, any]()
@@ -2952,6 +2979,7 @@ func YieldingDurations() {
 		}
 	}
 }
+
 //go:noinline
 func YieldAndDeferAssign(_fn0 *int, _fn1, _fn2 int) {
 	_c := coroutine.LoadContext[int, any]()
@@ -2996,6 +3024,7 @@ func YieldAndDeferAssign(_fn0 *int, _fn1, _fn2 int) {
 		coroutine.Yield[int, any](_f0.X1)
 	}
 }
+
 //go:noinline
 func RangeYieldAndDeferAssign(_fn0 int) {
 	_c := coroutine.LoadContext[int, any]()
@@ -3033,6 +3062,7 @@ func RangeYieldAndDeferAssign(_fn0 int) {
 }
 
 type MethodGeneratorState struct{ i int }
+
 //go:noinline
 func (_fn0 *MethodGeneratorState) MethodGenerator(_fn1 int) {
 	_c := coroutine.LoadContext[int, any]()
@@ -3069,6 +3099,7 @@ func (_fn0 *MethodGeneratorState) MethodGenerator(_fn1 int) {
 		}
 	}
 }
+
 //go:noinline
 func VarArgs(_fn0 int) {
 	_c := coroutine.LoadContext[int, any]()
@@ -3108,6 +3139,7 @@ func VarArgs(_fn0 int) {
 		varArgs(_f0.X1...)
 	}
 }
+
 //go:noinline
 func varArgs(_fn0 ...int) {
 	_c := coroutine.LoadContext[int, any]()
@@ -3164,6 +3196,7 @@ func varArgs(_fn0 ...int) {
 		}
 	}
 }
+
 //go:noinline
 func ReturnNamedValue() (_fn0 int) {
 	_c := coroutine.LoadContext[int, any]()
@@ -3203,21 +3236,26 @@ func ReturnNamedValue() (_fn0 int) {
 	}
 	panic("unreachable")
 }
+
 //go:noinline
-func IdentityGeneric[T any](n T) { coroutine.Yield[T, any](n) }
+func IdentityGeneric(n int) { coroutine.Yield[T, any](n) }
 
 type IdentityGenericStruct[T any] struct {
 	n T
 }
+
 //go:noinline
 func (i *IdentityGenericStruct[T]) Run() { coroutine.Yield[T, any](i.n) }
+
 //go:noinline
 func IdentityGenericInt(n int) { IdentityGeneric[int](n) }
+
 //go:noinline
 func IdentityGenericStructInt(n int) { (&IdentityGenericStruct[int]{n: n}).Run() }
+
 //go:noinline
-func IdentityGenericClosure[T any](_fn0 T) {
-	_c := coroutine.LoadContext[T, any]()
+func IdentityGenericClosure(_fn0 int) {
+	_c := coroutine.LoadContext[int, any]()
 	var _f0 *struct {
 		IP int
 		X0 T
@@ -3256,11 +3294,12 @@ func IdentityGenericClosure[T any](_fn0 T) {
 // TODO: add this go:noinline directive automatically
 //
 //go:noinline
-func buildClosure[T any](n T) func() {
+func buildClosure(n T) func() {
 	return func() {
 		coroutine.Yield[T, any](n)
 	}
 }
+
 //go:noinline
 func IdentityGenericClosureInt(n int) { IdentityGenericClosure[int](n) }
 func init() {
@@ -3271,10 +3310,10 @@ func init() {
 	_types.RegisterFunc[func(_fn0 int)]("github.com/stealthrocket/coroutine/compiler/testdata.FizzBuzzSwitchGenerator")
 	_types.RegisterFunc[func(n int)]("github.com/stealthrocket/coroutine/compiler/testdata.Identity")
 	_types.RegisterFunc[func(n int)]("github.com/stealthrocket/coroutine/compiler/testdata.IdentityGenericClosureInt")
-	_types.RegisterFunc[func[T any](_fn0 T)]("github.com/stealthrocket/coroutine/compiler/testdata.IdentityGenericClosure[go.shape.int]")
+	_types.RegisterFunc[func(_fn0 int)]("github.com/stealthrocket/coroutine/compiler/testdata.IdentityGenericClosure[go.shape.int]")
 	_types.RegisterFunc[func(n int)]("github.com/stealthrocket/coroutine/compiler/testdata.IdentityGenericInt")
 	_types.RegisterFunc[func(n int)]("github.com/stealthrocket/coroutine/compiler/testdata.IdentityGenericStructInt")
-	_types.RegisterFunc[func[T any](n T)]("github.com/stealthrocket/coroutine/compiler/testdata.IdentityGeneric[go.shape.int]")
+	_types.RegisterFunc[func(n int)]("github.com/stealthrocket/coroutine/compiler/testdata.IdentityGeneric[go.shape.int]")
 	_types.RegisterFunc[func(_ int)]("github.com/stealthrocket/coroutine/compiler/testdata.LoopBreakAndContinue")
 	_types.RegisterFunc[func(_fn1 int)]("github.com/stealthrocket/coroutine/compiler/testdata.MethodGenerator")
 	_types.RegisterFunc[func(_fn0 int) (_ int)]("github.com/stealthrocket/coroutine/compiler/testdata.NestedLoops")
@@ -3399,12 +3438,12 @@ func init() {
 	_types.RegisterFunc[func()]("github.com/stealthrocket/coroutine/compiler/testdata.YieldingExpressionDesugaring")
 	_types.RegisterFunc[func(_fn0 int) (_ int)]("github.com/stealthrocket/coroutine/compiler/testdata.a")
 	_types.RegisterFunc[func(_fn0 int) (_ int)]("github.com/stealthrocket/coroutine/compiler/testdata.b")
-	_types.RegisterFunc[func[T any](n T) func()]("github.com/stealthrocket/coroutine/compiler/testdata.buildClosure[go.shape.int]")
+	_types.RegisterFunc[func(n T) func()]("github.com/stealthrocket/coroutine/compiler/testdata.buildClosure[go.shape.int]")
 	_types.RegisterClosure[func(), struct {
 		F  uintptr
-		X0 T
+		X0 int
 	}]("github.com/stealthrocket/coroutine/compiler/testdata.buildClosure[go.shape.int].func1")
-	_types.RegisterFunc[func[T any](n T) func()]("github.com/stealthrocket/coroutine/compiler/testdata.buildClosure[go.shape.interface{}]")
+	_types.RegisterFunc[func(n T) func()]("github.com/stealthrocket/coroutine/compiler/testdata.buildClosure[go.shape.interface{}]")
 	_types.RegisterClosure[func(), struct {
 		F  uintptr
 		X0 T