Remove the 'Symbol' rule from the grammar.

[Hackerpilot]

http://forum.dlang.org/thread/[email protected]

The Symbol rule only appears as an alternative to the Type, AssignExpression, or Expression rules, but the Symbol rule is a subset of these other rules. Because of this, the grammar is ambiguous.

The difference between a type, expression, and symbol is something that can only be determined during semantic analysis, and thus should not be part of the parse grammar.

[WalterBright]

But a template argument to an alias parameter can be any symbol, such as a module name. A module name is neither a type nor an expression.

(Types and Expressions can also be ambiguous.)

[Hackerpilot]

I don't see what that kind of semantic information has to do with creating a parse tree, unless we're going the C++ route of requiring semantic in order to parse.

To clarify, a module name (e.g. std.experimental.allocator) parses as an expression through the PostfixExpression rule.