From 2d856e7dcf4c499e3648ffeb605c4b317290c8f0 Mon Sep 17 00:00:00 2001 From: Delyan Angelov Date: Sat, 1 Nov 2025 22:01:59 +0200 Subject: [PATCH] cgen: fix `fn (d Struct) a[T]() T { return d }` when T is a sumtype (#25644) --- vlib/v/gen/c/struct.v | 10 +++++++--- .../tests/sumtypes/sumtype_value_pointer_test.v | 17 +++++++++++++++++ 2 files changed, 24 insertions(+), 3 deletions(-) create mode 100644 vlib/v/tests/sumtypes/sumtype_value_pointer_test.v diff --git a/vlib/v/gen/c/struct.v b/vlib/v/gen/c/struct.v index ea0278d7a..d19eacabe 100644 --- a/vlib/v/gen/c/struct.v +++ b/vlib/v/gen/c/struct.v @@ -41,9 +41,13 @@ fn (mut g Gen) struct_init(node ast.StructInit) { mut sym := g.table.final_sym(unwrapped_typ) if sym.kind == .sum_type { if node.typ.has_flag(.generic) && unwrapped_typ.is_ptr() { - g.write('&(') - g.write(g.type_default_sumtype(unwrapped_typ.set_nr_muls(0), sym)) - g.write(')') + // handle promotions to a sumtype for generic functions like this one: `fn (d Struct) a[T]() T { return d }` + // the value should be on the heap, since it is not known where it will be used: + sumtype_type := unwrapped_typ.set_nr_muls(0) + sumtype_name := g.styp(sumtype_type) + g.write('HEAP(${sumtype_name}, (') + g.write(g.type_default_sumtype(sumtype_type, sym)) + g.write('))') } else { g.write(g.type_default_sumtype(unwrapped_typ, sym)) } diff --git a/vlib/v/tests/sumtypes/sumtype_value_pointer_test.v b/vlib/v/tests/sumtypes/sumtype_value_pointer_test.v new file mode 100644 index 000000000..37e8b392e --- /dev/null +++ b/vlib/v/tests/sumtypes/sumtype_value_pointer_test.v @@ -0,0 +1,17 @@ +struct Struct {} + +type SumType = Struct | int + +fn (d Struct) a[T]() T { + return T{} +} + +fn test_main() { + s := Struct{} + x := s.a[&SumType]() + assert x is Struct + println('first assert passed') + println(x) + assert x is Struct + println('second assert passed') +} -- 2.39.5