Disallow foo.bar(&block) do end

spec/compiler/parser/parser_spec.cr

@@ -812,7 +812,10 @@ module Crystal
     it_parses "1.foo do; 1; end", Call.new(1.int32, "foo", block: Block.new(body: 1.int32))
     it_parses "a b() {}", Call.new(nil, "a", Call.new(nil, "b", block: Block.new))
 
-    assert_syntax_error "foo(&block) {}"
+    assert_syntax_error "foo(&block) {}", "can't use captured and non-captured blocks together"
+    assert_syntax_error "foo(&block) do end", "can't use captured and non-captured blocks together"
+    assert_syntax_error "foo.bar(&block) {}", "can't use captured and non-captured blocks together"
+    assert_syntax_error "foo.bar(&block) do end", "can't use captured and non-captured blocks together"
 
     it_parses "foo { |a, (b, c), (d, e)| a; b; c; d; e }", Call.new(nil, "foo",
       block: Block.new(

src/compiler/crystal/syntax/parser.cr

@@ -788,6 +788,11 @@ module Crystal
             end
 
             block = parse_block(block, stop_on_do: @stop_on_do)
+
+            if block && block_arg
+              raise "can't use captured and non-captured blocks together", location
+            end
+
             atomic = Call.new atomic, name, (args || [] of ASTNode), block, block_arg, named_args
             atomic.has_parentheses = has_parentheses
             atomic.name_location = name_location