Catch overlap between class parameters and methods

While identifier resolution already caught conflicts between class
parameters and inherited methods, it didn't do the same for methods
declared locally. This commit adds the same check and suggestion for
locally-declared methods as well.

identifierresolution.grace

@@ -584,6 +584,7 @@ method resolveIdentifiers(topNode) {
             classScope.add(node.constructor.value)
             classScope.bindAs(node.name.value)
             pushScope
+            def paramScope = scope
             if (false != node.generics) then {
                 for (node.generics) do {g->
                     scope.add(g.value) as "def"
@@ -634,6 +635,22 @@ method resolveIdentifiers(topNode) {
                     }
                 }
             }
+            for (node.signature) do {s->
+                for (s.params) do {p->
+                    if (scope.elements.contains(p.value)) then {
+                        def suggestion = errormessages.suggestion.new
+                        suggestion.insert("'")atPosition(p.linePos + p.value.size)onLine(p.line)
+                        var primes := "'"
+                        while { scope.elements.contains(p.value ++ primes) || paramScope.elements.contains(p.value ++ primes) } do {
+                            suggestion.insert("'")atPosition(p.linePos + p.value.size)onLine(p.line)
+                            primes := primes ++ "'"
+                        }
+                        errormessages.syntaxError("The parameter name '{p.value}' cannot be used because this class declares something named '{p.value}'.")atRange(
+                            p.line, p.linePos, p.linePos + p.value.size - 1)withSuggestion(suggestion)
+
+                    }
+                }
+            }
         }
         if (node.kind == "object") then {
             pushScope