fix(token): default associative "right" to match yacc/bison shift-first behavior#48
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Without an explicit precedence declaration, S/R conflicts now resolve to shift (matching yacc/bison behavior) instead of reduce. Previously the "left" default caused reduce to always win at precedence 0, which made the dangling-else attach to the outer if instead of the inner one. Co-Authored-By: Claude Sonnet 4.6 <[email protected]>
- Add explicit associative="left" to PLUS_SR so the left-associativity test continues to pass under the new "right" default - Update Section 2 header and docstring to reflect that left-assoc now requires an explicit declaration rather than being the default - Remove @pytest.mark.xfail from test_dangling_else_inner_if_gets_else; else now correctly binds to the inner if (shift wins at precedence 0) Co-Authored-By: Claude Sonnet 4.6 <[email protected]>
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Summary
Token.associativedefault changed from"left"to"right"to shift (matching yacc/bison behavior) instead of reduce
if c1 then if c2 then s1 else s2now correctly produces
IfThenD(c1, IfThenElseD(c2, s1, s2))Root Cause
The S/R conflict resolution condition in
parser.py:With the old
"left"default, the second branch was always true atprecedence 0, so reduce always won — contradicting yacc/bison, which
defaults to shift when no declaration is present.
Migration
Grammars that relied on the implicit left-associativity of undeclared
tokens must now add an explicit
associative = "left"to their tokenclass (as done for
PLUS_SRin the test suite).Test Plan
test_dangling_else_inner_if_gets_else— xfail removed, now passestest_default_sr_conflict_is_left_associative— still passes with explicitassociative = "left"onPLUS_SR