cgen: fix closure code gen with if statement in definition (#12028)

vlib/v/gen/c/fn.v

@@ -425,20 +425,17 @@ fn (mut g Gen) gen_anon_fn(mut node ast.AnonFn) {
 		return
 	}
 	// it may be possible to optimize `memdup` out if the closure never leaves current scope
-	ctx_var := g.new_tmp_var()
-	cur_line := g.go_before_stmt(0)
 	ctx_struct := closure_ctx_struct(node.decl)
-	g.writeln('$ctx_struct* $ctx_var = ($ctx_struct*) memdup(&($ctx_struct){')
+	// TODO in case of an assignment, this should only call "__closure_set_data" and "__closure_set_function" (and free the former data)
+	g.write('__closure_create($node.decl.name, ${node.decl.params.len + 1}, ')
+	g.writeln('($ctx_struct*) memdup(&($ctx_struct){')
 	g.indent++
 	for var in node.inherited_vars {
 		g.writeln('.$var.name = $var.name,')
 	}
 	g.indent--
-	g.writeln('}, sizeof($ctx_struct));')
+	g.write('}, sizeof($ctx_struct)))')
 	g.empty_line = false
-	g.write(cur_line)
-	// TODO in case of an assignment, this should only call "__closure_set_data" and "__closure_set_function" (and free the former data)
-	g.write('__closure_create($node.decl.name, ${node.decl.params.len + 1}, $ctx_var)')
 }
 
 fn (mut g Gen) gen_anon_fn_decl(mut node ast.AnonFn) {

vlib/v/tests/closure_test.v

@@ -151,3 +151,20 @@ fn test_go_call_closure() {
 	assert <-ch == 15
 }
 */
+
+fn test_closures_with_ifstmt() {
+	a := 1
+	f := fn [a] (x int) int {
+		if a > x { return 1
+		 } else { return -1
+		 }
+	}
+	g := fn [a] () int {
+		if true {
+			return 1
+		}
+		return 0
+	}
+	assert f(0) == 1
+	assert g() == 1
+}