From 90ae3c82c97b507534840db8781571be706f910d Mon Sep 17 00:00:00 2001
From: yuyi <yuyi98@163.com>
Date: Thu, 2 Feb 2023 15:31:11 +0800
Subject: [PATCH] cgen: fix sumtype as cast with calling twice (fix #17156)
 (#17183)

---
 cmd/tools/vtest-self.v              |  1 +
 vlib/v/gen/c/cgen.v                 | 72 ++++++++++++++++++++++-------
 vlib/v/tests/sumtype_as_cast_test.v | 18 ++++++++
 3 files changed, 75 insertions(+), 16 deletions(-)
 create mode 100644 vlib/v/tests/sumtype_as_cast_test.v

diff --git a/cmd/tools/vtest-self.v b/cmd/tools/vtest-self.v
index b4c680837f..7d00689650 100644
--- a/cmd/tools/vtest-self.v
+++ b/cmd/tools/vtest-self.v
@@ -230,6 +230,7 @@ const (
 		'do_not_remove',
 		'vlib/v/tests/const_fixed_array_containing_references_to_itself_test.v', // error C2099: initializer is not a constant
 		'vlib/v/tests/const_and_global_with_same_name_test.v', // error C2099: initializer is not a constant
+		'vlib/v/tests/sumtype_as_cast_test.v', // error: Compound statement expression cannot support
 	]
 	skip_on_windows               = [
 		'do_not_remove',
diff --git a/vlib/v/gen/c/cgen.v b/vlib/v/gen/c/cgen.v
index ed1dcb59cb..4e877ae5d0 100644
--- a/vlib/v/gen/c/cgen.v
+++ b/vlib/v/gen/c/cgen.v
@@ -6088,23 +6088,63 @@ fn (mut g Gen) as_cast(node ast.AsCast) {
 	mut expr_type_sym := g.table.sym(g.unwrap_generic(node.expr_type))
 	if mut expr_type_sym.info is ast.SumType {
 		dot := if node.expr_type.is_ptr() { '->' } else { '.' }
-		if sym.info is ast.FnType {
-			g.write('/* as */ (${styp})__as_cast(')
-		} else {
-			g.write('/* as */ *(${styp}*)__as_cast(')
+		$if !msvc {
+			if node.expr is ast.CallExpr {
+				tmp_var := g.new_tmp_var()
+				expr_styp := g.typ(node.expr_type)
+				g.write('({ ${expr_styp} ${tmp_var} = ')
+				g.expr(node.expr)
+				g.write('; ')
+				if sym.info is ast.FnType {
+					g.write('/* as */ (${styp})__as_cast(')
+				} else {
+					g.write('/* as */ *(${styp}*)__as_cast(')
+				}
+				g.write(tmp_var)
+				g.write(dot)
+				g.write('_${sym.cname},')
+				g.write(tmp_var)
+				g.write(dot)
+				sidx := g.type_sidx(unwrapped_node_typ)
+				g.write('_typ, ${sidx}); }) /*expected idx: ${sidx}, name: ${sym.name} */ ')
+			} else {
+				if sym.info is ast.FnType {
+					g.write('/* as */ (${styp})__as_cast(')
+				} else {
+					g.write('/* as */ *(${styp}*)__as_cast(')
+				}
+				g.write('(')
+				g.expr(node.expr)
+				g.write(')')
+				g.write(dot)
+				g.write('_${sym.cname},')
+				g.write('(')
+				g.expr(node.expr)
+				g.write(')')
+				g.write(dot)
+				// g.write('typ, /*expected:*/$node.typ)')
+				sidx := g.type_sidx(unwrapped_node_typ)
+				g.write('_typ, ${sidx}) /*expected idx: ${sidx}, name: ${sym.name} */ ')
+			}
+		} $else {
+			if sym.info is ast.FnType {
+				g.write('/* as */ (${styp})__as_cast(')
+			} else {
+				g.write('/* as */ *(${styp}*)__as_cast(')
+			}
+			g.write('(')
+			g.expr(node.expr)
+			g.write(')')
+			g.write(dot)
+			g.write('_${sym.cname},')
+			g.write('(')
+			g.expr(node.expr)
+			g.write(')')
+			g.write(dot)
+			// g.write('typ, /*expected:*/$node.typ)')
+			sidx := g.type_sidx(unwrapped_node_typ)
+			g.write('_typ, ${sidx}) /*expected idx: ${sidx}, name: ${sym.name} */ ')
 		}
-		g.write('(')
-		g.expr(node.expr)
-		g.write(')')
-		g.write(dot)
-		g.write('_${sym.cname},')
-		g.write('(')
-		g.expr(node.expr)
-		g.write(')')
-		g.write(dot)
-		// g.write('typ, /*expected:*/$node.typ)')
-		sidx := g.type_sidx(unwrapped_node_typ)
-		g.write('_typ, ${sidx}) /*expected idx: ${sidx}, name: ${sym.name} */ ')
 
 		// fill as cast name table
 		for variant in expr_type_sym.info.variants {
diff --git a/vlib/v/tests/sumtype_as_cast_test.v b/vlib/v/tests/sumtype_as_cast_test.v
new file mode 100644
index 0000000000..a0a7569111
--- /dev/null
+++ b/vlib/v/tests/sumtype_as_cast_test.v
@@ -0,0 +1,18 @@
+type Sum = int | string
+
+struct Count {
+mut:
+	count int
+}
+
+fn (mut c Count) ret_sum() Sum {
+	c.count++
+	return c.count
+}
+
+fn test_sumtype_as_cast() {
+	mut cnt := Count{22}
+	_ := cnt.ret_sum() as int
+	println(cnt)
+	assert cnt.count == 23
+}