Fix - printing

Co-authored-by: "Shashi Gowda" <[email protected]>

Author: YingboMa

src/types.jl

@@ -370,7 +370,7 @@ function show_add(io, args)
             print_arg(io, -, t)
         else
             print(io, " - ")
-            print_arg(io, +, -t)
+            print_arg(IOContext(io, :paren=>true), +, -t)
         end
     end
 end

test/basics.jl

@@ -111,6 +111,8 @@ end
     @test repr(Term(*, [1, 1])) == "*1"
     @test repr(Term(*, [2, 1])) == "2*1"
     @test repr((a + b) - (b + c)) == "a - c"
+    @test repr(a + -1*(b + c)) == "a - (b + c)"
+    @test repr(a + -1*b) == "a - b"
 end
 
 toterm(t) = Term{symtype(t)}(operation(t), arguments(t))