feat(minifier): compress [] + string to string

crates/oxc_minifier/src/peephole/fold_constants.rs

@@ -467,9 +467,9 @@ impl<'a> PeepholeOptimizations {
         }
 
         // remove useless `+ ""` (e.g. `typeof foo + ""` -> `typeof foo`)
-        if left_expr.is_specific_string_literal("") && right_expr.value_type(&ctx).is_string() {
+        if Self::evaluates_to_empty_string(left_expr) && right_expr.value_type(&ctx).is_string() {
             return Some(ctx.ast.move_expression(right_expr));
-        } else if right_expr.is_specific_string_literal("")
+        } else if Self::evaluates_to_empty_string(right_expr)
             && left_expr.value_type(&ctx).is_string()
         {
             return Some(ctx.ast.move_expression(left_expr));
@@ -478,6 +478,14 @@ impl<'a> PeepholeOptimizations {
         None
     }
 
+    fn evaluates_to_empty_string(e: &Expression<'a>) -> bool {
+        match e {
+            Expression::StringLiteral(s) => s.value.is_empty(),
+            Expression::ArrayExpression(a) => a.elements.is_empty(),
+            _ => false,
+        }
+    }
+
     fn try_fold_left_child_op(
         e: &mut BinaryExpression<'a>,
         ctx: Ctx<'a, '_>,
@@ -1839,6 +1847,10 @@ mod test {
         fold_same("typeof foo + '123'");
         fold("typeof foo + ''", "typeof foo");
         fold("'' + typeof foo", "typeof foo");
+        fold("typeof foo + ``", "typeof foo");
+        fold("`` + typeof foo", "typeof foo");
+        fold("typeof foo + []", "typeof foo");
+        fold("[] + typeof foo", "typeof foo");
         fold("(foo ? 'a' : 'b') + ''", "foo ? 'a' : 'b'");
         fold_same("typeof foo - ''");
     }

crates/oxc_minifier/tests/peephole/esbuild.rs

@@ -315,8 +315,8 @@ fn js_parser_test() {
     test("a = typeof b + ''", "a = typeof b;");
     test("a = [] + `${b}`", "a = `${b}`;");
     test("a = `${b}` + []", "a = `${b}`;");
-    // test("a = [] + typeof b", "a = typeof b;");
-    // test("a = typeof b + []", "a = typeof b;");
+    test("a = [] + typeof b", "a = typeof b;");
+    test("a = typeof b + []", "a = typeof b;");
     test("a = [b] + `${b}`", "a = [b] + `${b}`;");
     test("a = `${b}` + [b]", "a = `${b}` + [b];");
     test("a = {} + `${b}`", "a = `[object Object]${b}`;");