From 82c9d4ab5bda5e2a2db0f3ad5181dc41a6f47a60 Mon Sep 17 00:00:00 2001
From: Felipe Pena <felipensp@gmail.com>
Date: Wed, 11 Dec 2024 01:07:29 -0300
Subject: [PATCH] checker, cgen: fix codegen for returning different option
 alias type (fix #23087) (#23125)

---
 vlib/builtin/option.v                         | 13 +++++++
 vlib/v/checker/return.v                       |  2 +-
 vlib/v/gen/c/assign.v                         | 37 +++++++++++--------
 vlib/v/gen/c/cgen.v                           | 10 ++++-
 .../tests/options/option_alias_fn_ret_test.v  | 22 +++++++++++
 5 files changed, 66 insertions(+), 18 deletions(-)
 create mode 100644 vlib/v/tests/options/option_alias_fn_ret_test.v

diff --git a/vlib/builtin/option.v b/vlib/builtin/option.v
index dfd246758..c11b4a4c6 100644
--- a/vlib/builtin/option.v
+++ b/vlib/builtin/option.v
@@ -41,6 +41,19 @@ fn _option_ok(data voidptr, mut option _option, size int) {
 	}
 }
 
+@[markused]
+fn _option_clone(current &_option, mut option _option, size int) {
+	unsafe {
+		*option = _option{
+			state: current.state
+			err:   current.err
+		}
+		// use err to get the end of OptionBase and then memcpy into it
+		vmemcpy(&u8(&option.err) + sizeof(IError), &u8(&current.err) + sizeof(IError),
+			size)
+	}
+}
+
 //
 
 const none__ = IError(&None__{})
diff --git a/vlib/v/checker/return.v b/vlib/v/checker/return.v
index e970f72dc..dc80406f2 100644
--- a/vlib/v/checker/return.v
+++ b/vlib/v/checker/return.v
@@ -197,7 +197,7 @@ fn (mut c Checker) return_stmt(mut node ast.Return) {
 		}
 		got_type := c.unwrap_generic(got_types[i])
 		if got_type.has_flag(.option) && (!exp_type.has_flag(.option)
-			|| got_type.clear_flag(.option) != exp_type.clear_flag(.option)) {
+			|| !c.check_types(got_type.clear_flag(.option), exp_type.clear_flag(.option))) {
 			pos := node.exprs[expr_idxs[i]].pos()
 			c.error('cannot use `${c.table.type_to_str(got_type)}` as ${c.error_type_name(exp_type)} in return argument',
 				pos)
diff --git a/vlib/v/gen/c/assign.v b/vlib/v/gen/c/assign.v
index 0232004d2..f05fbc719 100644
--- a/vlib/v/gen/c/assign.v
+++ b/vlib/v/gen/c/assign.v
@@ -68,28 +68,35 @@ fn (mut g Gen) expr_opt_with_cast(expr ast.Expr, expr_typ ast.Type, ret_typ ast.
 		defer {
 			g.past_tmp_var_done(past)
 		}
-
 		styp := g.base_type(ret_typ)
 		decl_styp := g.styp(ret_typ).replace('*', '_ptr')
 		g.writeln('${decl_styp} ${past.tmp_var};')
 		is_none := expr is ast.CastExpr && expr.expr is ast.None
-		if is_none {
-			g.write('_option_none(&(${styp}[]) {')
-		} else {
-			g.write('_option_ok(&(${styp}[]) {')
-		}
-		if expr is ast.CastExpr && expr_typ.has_flag(.option) {
-			g.write('*((${g.base_type(expr_typ)}*)')
+		if expr is ast.CallExpr && expr.return_type.has_flag(.option) {
+			tmp_var := g.new_tmp_var()
+			ret_styp := g.styp(expr.return_type).replace('*', '_ptr')
+			g.write('${ret_styp} ${tmp_var} = ')
 			g.expr(expr)
-			g.write('.data)')
+			g.writeln(';')
+			g.writeln('_option_clone(&${tmp_var}, (${option_name}*)(&${past.tmp_var}), sizeof(${styp}));')
 		} else {
-			old_inside_opt_or_res := g.inside_opt_or_res
-			g.inside_opt_or_res = false
-			g.expr_with_cast(expr, expr_typ, ret_typ)
-			g.inside_opt_or_res = old_inside_opt_or_res
+			if is_none {
+				g.write('_option_none(&(${styp}[]) {')
+			} else {
+				g.write('_option_ok(&(${styp}[]) {')
+			}
+			if expr is ast.CastExpr && expr_typ.has_flag(.option) {
+				g.write('*((${g.base_type(expr_typ)}*)')
+				g.expr(expr)
+				g.write('.data)')
+			} else {
+				old_inside_opt_or_res := g.inside_opt_or_res
+				g.inside_opt_or_res = false
+				g.expr_with_cast(expr, expr_typ, ret_typ)
+				g.inside_opt_or_res = old_inside_opt_or_res
+			}
+			g.writeln(' }, (${option_name}*)(&${past.tmp_var}), sizeof(${styp}));')
 		}
-		g.writeln(' }, (${option_name}*)(&${past.tmp_var}), sizeof(${styp}));')
-
 		return past.tmp_var
 	}
 }
diff --git a/vlib/v/gen/c/cgen.v b/vlib/v/gen/c/cgen.v
index 301a66538..978ba1dab 100644
--- a/vlib/v/gen/c/cgen.v
+++ b/vlib/v/gen/c/cgen.v
@@ -5631,7 +5631,6 @@ fn (mut g Gen) return_stmt(node ast.Return) {
 	fn_return_is_fixed_array := sym.is_array_fixed()
 	fn_return_is_fixed_array_non_result := fn_return_is_fixed_array
 		&& !fn_ret_type.has_option_or_result()
-
 	mut has_semicolon := false
 	if node.exprs.len == 0 {
 		g.write_defer_stmts_when_needed()
@@ -6020,7 +6019,14 @@ fn (mut g Gen) return_stmt(node ast.Return) {
 			}
 		} else {
 			if g.fn_decl.return_type.has_flag(.option) {
-				g.expr_with_opt(node.exprs[0], node.types[0], g.fn_decl.return_type)
+				expr0_is_alias_fn_ret := expr0 is ast.CallExpr && node.types[0].has_flag(.option)
+					&& g.table.type_kind(node.types[0]) in [.placeholder, .alias]
+				// return foo() where foo() returns different option alias than current fn
+				if expr0_is_alias_fn_ret {
+					g.expr_opt_with_cast(node.exprs[0], node.types[0], g.fn_decl.return_type)
+				} else {
+					g.expr_with_opt(node.exprs[0], node.types[0], g.fn_decl.return_type)
+				}
 			} else {
 				if fn_return_is_fixed_array && !node.types[0].has_option_or_result() {
 					if node.exprs[0] is ast.Ident {
diff --git a/vlib/v/tests/options/option_alias_fn_ret_test.v b/vlib/v/tests/options/option_alias_fn_ret_test.v
new file mode 100644
index 000000000..4cf7730fa
--- /dev/null
+++ b/vlib/v/tests/options/option_alias_fn_ret_test.v
@@ -0,0 +1,22 @@
+import time
+
+fn test() ?i64 {
+	return bar()
+}
+
+fn test2() ?i64 {
+	return none
+}
+
+fn bar() ?time.Duration {
+	return time.Duration(0)
+}
+
+fn baz() ?time.Duration {
+	return none
+}
+
+fn test_main() {
+	assert test() != none
+	assert test2() == none
+}
-- 
2.39.5