wasm: fix string plus assign with call expr (#26287)

Author: Krchi

vlib/v/gen/wasm/gen.v

@@ -1365,9 +1365,13 @@ pub fn (mut g Gen) expr_stmt(node ast.Stmt, expected ast.Type) {
 						}
 					}
 
-					if !passed && node.op == .assign {
-						if v := g.get_var_from_expr(left) {
-							var = v
+					if !passed {
+						if node.op == .assign {
+							if v := g.get_var_from_expr(left) {
+								var = v
+							}
+						} else if node.op == .plus_assign && g.is_param_type(rt) {
+							var = g.new_local('', rt)
 						}
 					}
 

vlib/v/gen/wasm/tests/builtin.vv

@@ -118,6 +118,12 @@ fn str_implicit() {
 	println(a + 10)
 }
 
+fn str_plus_assign_with_call_expr() {
+	mut str := 'a'
+	str += 1.str()
+	println(str)
+}
+
 fn assertions() {
 	assert true, 'hello'
 	assert true
@@ -133,6 +139,7 @@ fn main() {
 	str_cmp()
 	str_loop_concat()
 	str_literal()
+	str_plus_assign_with_call_expr()
 	assertions()
 
 	// panic('nooo!')

vlib/v/gen/wasm/tests/builtin.vv.out

@@ -43,6 +43,7 @@ Such wow
 Helllo!
 42
 0 - 1 - 2 - 3 - 4 - 5 - 6 - 7 - 8 - 9 - 10!
+a1
 wasm builtins
 1
-1
+1