2009-03-22 Miguel de Icaza <miguel@novell.com>

2009-03-22  Miguel de Icaza  <miguel@novell.com>

	Initial support to provide code completion facilities to consumers
	of the evaluator API.

	* cs-tokenizer.cs (CompleteOnEOF): this new property is used to
	support the completion engine.   When we reach the end of the
	input stream instead of returning EOF, when this flag is true the
	tokenizer instead produces:

		One GENERATE_COMPLETION token: this token then must be
		handled in the grammar at every point where the user
		would likely request a completion.

		As many COMPLETE_COMPLETION tokens as necessary.   These
		tokens are generated to assist the parser in unwinding and
		producing a valid parse tree.

	The parser rules do not have to be perfect, the parser needs to be
	augmented with judicious use of GENERATE_COMPLETION tokens to
	improve the areas where we can provide completion and the parser
	needs to add support for COMPLETE_COMPLETION tokens in productions
	to make them work.

	It is common to not have enough support for COMPLETE_COMPLETION
	under certain rules and that even if we generated the
	GENERATE_COMPLETION token that the resulting tree will be invalid
	due to the missing rules that support COMPLETE_COMPLETION.

	The final EOF token is produced by having the parser notify the
	tokenizer when it reaches the root production that the next token
	should be EOF.

	* support.cs (CompletionResult): New Exception.   This exception
	is thrown to return the completion results when one of the special
	completion expressions is reached.

	This exception is thrown by the completing ExpressionStatements
	classes that live in complete.cs

	* complete.cs (CompletingExpression): a new base class for
	completing expressions.   This derives from the
	ExpressionStatement class and not from Expression as it allows
	completion to happen not only where expressions are expected in
	the grammar, but also where statements are expected.

	(CompletionSimpleName): A new class used to provide completions
	for SimpleNames.     This currently only resolves to local
	variables from the evaluator context (GetVars call).

	(CompletionMemberAccess): Implements support for completing member
	access patterns.

	* cs-parser.jay: Add support for completion in a few places.

	* eval.cs (GetCompletions): New public API for the evaluator that
	returns a list of possible completions given the input.   The
	return value is an array of completions

	* anonymous.cs (Compatible): If the exception thrown from the
	resolved expression is a CompletionResult exception let that one
	through instead of printing a diagnostic error in the try/catch.

svn path=/trunk/mcs/; revision=132033