diff --git a/compiler/testdata/generics.go b/compiler/testdata/generics.go
index fc35538fe..76169ce5f 100644
--- a/compiler/testdata/generics.go
+++ b/compiler/testdata/generics.go
@@ -19,12 +19,49 @@ func Add[T Coord](a, b Point[T]) Point[T] {
 	}
 }
 
+func aliasSize[F float32 | float64]() uintptr {
+	return unsafe.Sizeof(F(0))
+}
+
+func aliasSize32() uintptr {
+	type F = float32
+	return aliasSize[F]()
+}
+
+func aliasSize64() uintptr {
+	type F = float64
+	return aliasSize[F]()
+}
+
+type aliasMethodResult[F float32 | float64] struct {
+	Value F
+}
+
+type aliasMethodValue[F float32 | float64] struct{}
+
+func (aliasMethodValue[F]) Get() aliasMethodResult[F] {
+	return aliasMethodResult[F]{}
+}
+
 func main() {
 	var af, bf Point[float32]
 	Add(af, bf)
 
 	var ai, bi Point[int]
 	Add(ai, bi)
+
+	checkSize(aliasSize32())
+	checkSize(aliasSize64())
 }
 
 func checkSize(uintptr)
+
+func checkBool(bool)
+
+func aliasMethod32(x any) {
+	type F = float32
+	_, ok := x.(interface {
+		Get() aliasMethodResult[F]
+	})
+	checkBool(ok)
+}
diff --git a/compiler/testdata/generics.ll b/compiler/testdata/generics.ll
index 2a3fcd0ab..abe80e2ed 100644
--- a/compiler/testdata/generics.ll
+++ b/compiler/testdata/generics.ll
@@ -14,11 +14,35 @@ entry:
   ret void
 }
 
+; Function Attrs: nounwind
+define hidden i32 @main.aliasSize32(ptr %context) unnamed_addr #1 {
+entry:
+  %0 = call i32 @"main.aliasSize[main.F]"(ptr undef)
+  ret i32 %0
+}
+
+; Function Attrs: nounwind
+define linkonce_odr hidden i32 @"main.aliasSize[main.F]"(ptr %context) unnamed_addr #1 {
+entry:
+  ret i32 4
+}
+
+; Function Attrs: nounwind
+define hidden i32 @main.aliasSize64(ptr %context) unnamed_addr #1 {
+entry:
+  %0 = call i32 @"main.aliasSize[main.F]"(ptr undef)
+  ret i32 %0
+}
+
 ; Function Attrs: nounwind
 define hidden void @main.main(ptr %context) unnamed_addr #1 {
 entry:
   %0 = call %"main.Point[float32]" @"main.Add[float32]"(float 0.000000e+00, float 0.000000e+00, float 0.000000e+00, float 0.000000e+00, ptr undef)
   %1 = call %"main.Point[int]" @"main.Add[int]"(i32 0, i32 0, i32 0, i32 0, ptr undef)
+  %2 = call i32 @main.aliasSize32(ptr undef)
+  call void @main.checkSize(i32 %2, ptr undef) #4
+  %3 = call i32 @main.aliasSize64(ptr undef)
+  call void @main.checkSize(i32 %3, ptr undef) #4
   ret void
 }
 
@@ -26,20 +50,20 @@ entry:
 define linkonce_odr hidden %"main.Point[float32]" @"main.Add[float32]"(float %a.X, float %a.Y, float %b.X, float %b.Y, ptr %context) unnamed_addr #1 {
 entry:
   %stackalloc = alloca i8, align 1
-  %a = call align 4 dereferenceable(8) ptr @runtime.alloc(i32 8, ptr nonnull inttoptr (i32 3 to ptr), ptr undef) #3
-  call void @runtime.trackPointer(ptr nonnull %a, ptr nonnull %stackalloc, ptr undef) #3
+  %a = call align 4 dereferenceable(8) ptr @runtime.alloc(i32 8, ptr nonnull inttoptr (i32 3 to ptr), ptr undef) #4
+  call void @runtime.trackPointer(ptr nonnull %a, ptr nonnull %stackalloc, ptr undef) #4
   store float %a.X, ptr %a, align 4
   %a.repack5 = getelementptr inbounds nuw i8, ptr %a, i32 4
   store float %a.Y, ptr %a.repack5, align 4
-  %b = call align 4 dereferenceable(8) ptr @runtime.alloc(i32 8, ptr nonnull inttoptr (i32 3 to ptr), ptr undef) #3
-  call void @runtime.trackPointer(ptr nonnull %b, ptr nonnull %stackalloc, ptr undef) #3
+  %b = call align 4 dereferenceable(8) ptr @runtime.alloc(i32 8, ptr nonnull inttoptr (i32 3 to ptr), ptr undef) #4
+  call void @runtime.trackPointer(ptr nonnull %b, ptr nonnull %stackalloc, ptr undef) #4
   store float %b.X, ptr %b, align 4
   %b.repack7 = getelementptr inbounds nuw i8, ptr %b, i32 4
   store float %b.Y, ptr %b.repack7, align 4
-  call void @main.checkSize(i32 4, ptr undef) #3
-  call void @main.checkSize(i32 8, ptr undef) #3
-  %complit = call align 4 dereferenceable(8) ptr @runtime.alloc(i32 8, ptr nonnull inttoptr (i32 3 to ptr), ptr undef) #3
-  call void @runtime.trackPointer(ptr nonnull %complit, ptr nonnull %stackalloc, ptr undef) #3
+  call void @main.checkSize(i32 4, ptr undef) #4
+  call void @main.checkSize(i32 8, ptr undef) #4
+  %complit = call align 4 dereferenceable(8) ptr @runtime.alloc(i32 8, ptr nonnull inttoptr (i32 3 to ptr), ptr undef) #4
+  call void @runtime.trackPointer(ptr nonnull %complit, ptr nonnull %stackalloc, ptr undef) #4
   br i1 false, label %deref.throw, label %deref.next
 
 deref.next:                                       ; preds = %entry
@@ -89,20 +113,20 @@ declare void @runtime.nilPanic(ptr) #0
 define linkonce_odr hidden %"main.Point[int]" @"main.Add[int]"(i32 %a.X, i32 %a.Y, i32 %b.X, i32 %b.Y, ptr %context) unnamed_addr #1 {
 entry:
   %stackalloc = alloca i8, align 1
-  %a = call align 4 dereferenceable(8) ptr @runtime.alloc(i32 8, ptr nonnull inttoptr (i32 3 to ptr), ptr undef) #3
-  call void @runtime.trackPointer(ptr nonnull %a, ptr nonnull %stackalloc, ptr undef) #3
+  %a = call align 4 dereferenceable(8) ptr @runtime.alloc(i32 8, ptr nonnull inttoptr (i32 3 to ptr), ptr undef) #4
+  call void @runtime.trackPointer(ptr nonnull %a, ptr nonnull %stackalloc, ptr undef) #4
   store i32 %a.X, ptr %a, align 4
   %a.repack5 = getelementptr inbounds nuw i8, ptr %a, i32 4
   store i32 %a.Y, ptr %a.repack5, align 4
-  %b = call align 4 dereferenceable(8) ptr @runtime.alloc(i32 8, ptr nonnull inttoptr (i32 3 to ptr), ptr undef) #3
-  call void @runtime.trackPointer(ptr nonnull %b, ptr nonnull %stackalloc, ptr undef) #3
+  %b = call align 4 dereferenceable(8) ptr @runtime.alloc(i32 8, ptr nonnull inttoptr (i32 3 to ptr), ptr undef) #4
+  call void @runtime.trackPointer(ptr nonnull %b, ptr nonnull %stackalloc, ptr undef) #4
   store i32 %b.X, ptr %b, align 4
   %b.repack7 = getelementptr inbounds nuw i8, ptr %b, i32 4
   store i32 %b.Y, ptr %b.repack7, align 4
-  call void @main.checkSize(i32 4, ptr undef) #3
-  call void @main.checkSize(i32 8, ptr undef) #3
-  %complit = call align 4 dereferenceable(8) ptr @runtime.alloc(i32 8, ptr nonnull inttoptr (i32 3 to ptr), ptr undef) #3
-  call void @runtime.trackPointer(ptr nonnull %complit, ptr nonnull %stackalloc, ptr undef) #3
+  call void @main.checkSize(i32 4, ptr undef) #4
+  call void @main.checkSize(i32 8, ptr undef) #4
+  %complit = call align 4 dereferenceable(8) ptr @runtime.alloc(i32 8, ptr nonnull inttoptr (i32 3 to ptr), ptr undef) #4
+  call void @runtime.trackPointer(ptr nonnull %complit, ptr nonnull %stackalloc, ptr undef) #4
   br i1 false, label %deref.throw, label %deref.next
 
 deref.next:                                       ; preds = %entry
@@ -141,7 +165,26 @@ deref.throw:                                      ; preds = %store.next, %deref.
   unreachable
 }
 
+declare void @main.checkBool(i1, ptr) #0
+
+; Function Attrs: nounwind
+define hidden void @main.aliasMethod32(ptr %x.typecode, ptr %x.value, ptr %context) unnamed_addr #1 {
+entry:
+  %0 = call i1 @"interface:{Get:func:{}{named:main.aliasMethodResult[main.F]}}.$typeassert"(ptr %x.typecode) #4
+  br i1 %0, label %typeassert.ok, label %typeassert.next
+
+typeassert.next:                                  ; preds = %typeassert.ok, %entry
+  call void @main.checkBool(i1 %0, ptr undef) #4
+  ret void
+
+typeassert.ok:                                    ; preds = %entry
+  br label %typeassert.next
+}
+
+declare i1 @"interface:{Get:func:{}{named:main.aliasMethodResult[main.F]}}.$typeassert"(ptr) #3
+
 attributes #0 = { "target-features"="+bulk-memory,+bulk-memory-opt,+call-indirect-overlong,+mutable-globals,+nontrapping-fptoint,+sign-ext,-multivalue,-reference-types" }
 attributes #1 = { nounwind "target-features"="+bulk-memory,+bulk-memory-opt,+call-indirect-overlong,+mutable-globals,+nontrapping-fptoint,+sign-ext,-multivalue,-reference-types" }
 attributes #2 = { allockind("alloc,zeroed") allocsize(0) "alloc-family"="runtime.alloc" "target-features"="+bulk-memory,+bulk-memory-opt,+call-indirect-overlong,+mutable-globals,+nontrapping-fptoint,+sign-ext,-multivalue,-reference-types" }
-attributes #3 = { nounwind }
+attributes #3 = { "target-features"="+bulk-memory,+bulk-memory-opt,+call-indirect-overlong,+mutable-globals,+nontrapping-fptoint,+sign-ext,-multivalue,-reference-types" "tinygo-methods"="reflect/methods.Get() main.aliasMethodResult[main.F]" }
+attributes #4 = { nounwind }
diff --git a/testdata/localtypes.go b/testdata/localtypes.go
index f9081d00b..8960ca713 100644
--- a/testdata/localtypes.go
+++ b/testdata/localtypes.go
@@ -1,6 +1,9 @@
 package main
 
-import "reflect"
+import (
+	"reflect"
+	"unsafe"
+)
 
 type checker = func(any) bool
 
@@ -216,6 +219,92 @@ func issue5180CopyIgnoreNilMembers() (ok bool) {
 	return ok
 }
 
+func aliasSize[F float32 | float64]() int {
+	return 8 * int(unsafe.Sizeof(F(0)))
+}
+
+func aliasSizeCaller32() int {
+	type F = float32
+	return aliasSize[F]()
+}
+
+func aliasSizeCaller64() int {
+	type F = float64
+	return aliasSize[F]()
+}
+
+func aliasLocal[F float32 | float64]() (any, checker) {
+	type Local struct{ Value F }
+	return Local{}, func(x any) bool {
+		_, ok := x.(Local)
+		return ok
+	}
+}
+
+func aliasLocalCaller32() (any, checker) {
+	type F = float32
+	return aliasLocal[F]()
+}
+
+func aliasLocalCaller64() (any, checker) {
+	type F = float64
+	return aliasLocal[F]()
+}
+
+type aliasBox[F float32 | float64] struct {
+	Value F
+}
+
+func (b aliasBox[F]) Get() F {
+	return b.Value
+}
+
+func aliasBoxCaller32() bool {
+	type F = float32
+	var box any = aliasBox[F]{Value: 32}
+	_, ok := box.(interface{ Get() float32 })
+	return ok
+}
+
+func aliasBoxCaller64() bool {
+	type F = float64
+	var box any = aliasBox[F]{Value: 64}
+	_, ok := box.(interface{ Get() float64 })
+	return ok
+}
+
+type aliasMethodResult[F float32 | float64] struct {
+	Value F
+}
+
+type aliasMethodBox[F float32 | float64] struct {
+	Value F
+}
+
+func (b aliasMethodBox[F]) Get() aliasMethodResult[F] {
+	return aliasMethodResult[F]{Value: b.Value}
+}
+
+func aliasMethodCaller32() (any, checker) {
+	type F = float32
+	return aliasMethodBox[F]{Value: 32}, func(x any) bool {
+		_, ok := x.(interface {
+			Get() aliasMethodResult[F]
+		})
+		return ok
+	}
+}
+
+func aliasMethodCaller64() (any, checker) {
+	type F = float64
+	return aliasMethodBox[F]{Value: 64}, func(x any) bool {
+		_, ok := x.(interface {
+			Get() aliasMethodResult[F]
+		})
+		return ok
+	}
+}
+
 func main() {
 	expect("issue5180 TestCopy1", issue5180Copy1())
 	expect("issue5180 TestCopyIgnoreNilMembers", issue5180CopyIgnoreNilMembers())
@@ -300,4 +389,20 @@ func main() {
 	println("issue4931PairB labels:", issue4931PairB())
 	println("issue4931MethodA labels:", issue4931MethodA())
 	println("issue4931MethodB labels:", issue4931MethodB())
+	expect("aliasSize[float32]==32", aliasSizeCaller32() == 32)
+	expect("aliasSize[float64]==64", aliasSizeCaller64() == 64)
+	aliasLocal32, aliasLocalCheck32 := aliasLocalCaller32()
+	aliasLocal64, aliasLocalCheck64 := aliasLocalCaller64()
+	expect("aliasLocal[float32] accepts own", aliasLocalCheck32(aliasLocal32))
+	expect("aliasLocal[float64] accepts own", aliasLocalCheck64(aliasLocal64))
+	expect("aliasLocal[float32] rejects [float64]", !aliasLocalCheck32(aliasLocal64))
+	expect("aliasLocal[float64] rejects [float32]", !aliasLocalCheck64(aliasLocal32))
+	expect("aliasBox[float32] implements Get() float32", aliasBoxCaller32())
+	expect("aliasBox[float64] implements Get() float64", aliasBoxCaller64())
+	aliasMethod32, aliasMethodCheck32 := aliasMethodCaller32()
+	aliasMethod64, aliasMethodCheck64 := aliasMethodCaller64()
+	expect("aliasMethod[float32] accepts own", aliasMethodCheck32(aliasMethod32))
+	expect("aliasMethod[float64] accepts own", aliasMethodCheck64(aliasMethod64))
+	expect("aliasMethod[float32] rejects [float64]", !aliasMethodCheck32(aliasMethod64))
+	expect("aliasMethod[float64] rejects [float32]", !aliasMethodCheck64(aliasMethod32))
 }
diff --git a/testdata/localtypes.txt b/testdata/localtypes.txt
index dd5d72ddd..85a851741 100644
--- a/testdata/localtypes.txt
+++ b/testdata/localtypes.txt
@@ -47,3 +47,15 @@ issue4931PairA labels: 0
 issue4931PairB labels: 0
 issue4931MethodA labels: 0
 issue4931MethodB labels: 0
+ok: aliasSize[float32]==32
+BUG: aliasSize[float64]==64
+ok: aliasLocal[float32] accepts own
+ok: aliasLocal[float64] accepts own
+BUG: aliasLocal[float32] rejects [float64]
+BUG: aliasLocal[float64] rejects [float32]
+ok: aliasBox[float32] implements Get() float32
+BUG: aliasBox[float64] implements Get() float64
+ok: aliasMethod[float32] accepts own
+ok: aliasMethod[float64] accepts own
+BUG: aliasMethod[float32] rejects [float64]
+BUG: aliasMethod[float64] rejects [float32]