Add hint in case of missing operator (#40304)

* Add hint for missing operators

* Move hint to it's own error type

* Clear the hint handler after displaying hint

* Don't clear the already empty array in tests

* Don't pop the hint handler

* Rename handler

Author: Sov-trotter

base/errorshow.jl

@@ -319,6 +319,7 @@ function showerror(io::IO, ex::MethodError)
                       "\nYou can convert to a column vector with the vec() function.")
         end
     end
+    Experimental.register_error_hint(noncallable_number_hint_handler, MethodError)
     Experimental.show_error_hints(io, ex, arg_types_param, kwargs)
     try
         show_method_candidates(io, ex, kwargs)
@@ -879,3 +880,14 @@ function show(io::IO, ip::InterpreterIP)
         print(io, " in $(ip.code) at statement $(Int(ip.stmt))")
     end
 end
+
+# handler for displaying a hint in case the user tries to call
+# the instance of a number(misses out hte operator)
+# eg: (1 + 2)(3 + 4)
+function noncallable_number_hint_handler(io, ex, arg_types, kwargs)
+    if ex.f isa Number
+        print(io, "\nMaybe you forgot to use an operator such as ")
+        printstyled(io, "*, ^, %, / etc. ", color=:cyan)
+        print(io, "?")
+    end
+end

test/errorshow.jl

@@ -634,6 +634,13 @@ catch ex
 end
 pop!(Base.Experimental._hint_handlers[DomainError])  # order is undefined, don't copy this
 
+let err_str
+    err_str = @except_str (1 + 2)(3 + 4) MethodError
+    @test occursin("objects of type $(typeof(3)) are not callable", err_str)
+    @test occursin("Maybe you forgot to use an operator such as *, ^, %, / etc. ?", err_str)
+end
+pop!(Base.Experimental._hint_handlers[MethodError])  # order is undefined, don't copy this
+
 # Execute backtrace once before checking formatting, see #38858
 backtrace()