Fix incorrect location for parenthesized union AST nodes (#16552)

Author: Sija

spec/compiler/parser/parser_spec.cr

@@ -3424,6 +3424,19 @@ module Crystal
       node_source(source, expressions[1].as(TypeDeclaration).var).should eq("buzz")
     end
 
+    it "sets correct location of a parenthesized union" do
+      source = "foo : (String | Nil) | Foo"
+      node = Parser.new(source).parse.as(TypeDeclaration)
+
+      union = node.declared_type.should be_a Union
+      node_source(source, union)
+        .should eq("(String | Nil) | Foo")
+
+      inner_union = union.types.first.should be_a Union
+      node_source(source, inner_union)
+        .should eq("(String | Nil)")
+    end
+
     it "doesn't override yield with macro yield" do
       parser = Parser.new("def foo; yield 1; {% begin %} yield 1 {% end %}; end")
       a_def = parser.parse.as(Def)

src/compiler/crystal/syntax/parser.cr

@@ -5053,7 +5053,7 @@ module Crystal
         types << parse_atomic_type_with_suffix
       end
 
-      Union.new(types).at(types.first).at_end(types.last)
+      Union.new(types).at(type).at_end(types.last)
     end
 
     def parse_atomic_type_with_suffix
@@ -5101,6 +5101,9 @@ module Crystal
       when .op_lparen?
         next_token_skip_space_or_newline
         type = parse_type_splat { parse_union_type }
+        if type.is_a?(Union)
+          type.at(location).at_end(@token.location)
+        end
         if @token.type.op_rparen?
           next_token_skip_space
           if @token.type.op_minus_gt? # `(A) -> B` case