Fix parsing of 'with' inside streaming operator. #1504
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The stream expression has an expression followed by
an optional 'with' '[' array_range_expression ']'
(LRM 11.4.14)
There are a few other cases where an expression can
be trailed with 'with',
with_constraint_block: there we expect an
identifier list in parenthesis after 'with'
similar with array methods with predicate
with '(' ...)
Since the parser with one look-ahead can't see beyond
the 'with', it runs into a shift/reduce conflict
as it does not know if '(' or '[' is to follow.
Disambiguate that in the lexer by creating a
separate token TK_with__followed_by_bracket which is
a TK_with, where the lexer already looked ahead and
knows that it will be followed by '['.
After seeing the '[', everything but the "with" is put
back into the stream to be processed separately.
Changed lexer and parser as well as associated unit tests including formatter.
Fixing chipsalliance#693
Signed-off-by: Henner Zeller <hzeller@google.com>
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Hey @msierszulski maybe this would be something interesting for you to pick up ? I started it a long time ago in #697 but then became busy with other things so I didn't have the time to implement the reviewer-suggested changes. Since you're currently actively looking at the yacc file in other contexts, maybe this would be something interesting for you to make a fresh pull request out of that implements the reviewer suggestions from back then ? |
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This is picking up where we left off in #697. Mostly the strong suggestion there was to use lexer states which has to be explored here
The stream expression has an expression followed by an optional 'with' '[' array_range_expression ']'
(LRM 11.4.14)
There are a few other cases where an expression can be trailed with 'with',
with_constraint_block: there we expect an
identifier list in parenthesis after 'with'
similar with array methods with predicate
with '(' ...)
Since the parser with one look-ahead can't see beyond the 'with', it runs into a shift/reduce conflict
as it does not know if '(' or '[' is to follow.
Disambiguate that in the lexer by creating a
separate token TK_with__followed_by_bracket which is a TK_with, where the lexer already looked ahead and knows that it will be followed by '['.
After seeing the '[', everything but the "with" is put back into the stream to be processed separately.
Changed lexer and parser as well as associated unit tests including formatter.
Fixing #693