I have tried to follow the advice on fixing dangling else problem for an assignments grammar but I can't quite get it. I still have the a single shift/reduce conflict. I can't use assoc or left nor right for the Bison file.
I have tried to exhaust all of the posts on StackOverflow and gone through Google to no avail.
ConditionStmt
: ClosedStatement { $$ = $1;}
| OpenStatement {$$ = $1; }
;
OpenStatement
: "if" SimpleExpression "then" Statement {$$ = ast::action::MakeStatement<ast::Branch>({$2, $4}, @1, ast::BranchType::kIf); }
| "if" SimpleExpression "then" ClosedStatement "else" OpenStatement {$$ = ast::action::MakeStatement<ast::Branch>({$2, $4, $6}, @1, ast::BranchType::kIf); }
| "while" SimpleExpression "do" OpenStatement { $$ = ast::action::MakeStatement<ast::Iterator>({$2, $4}, @1, ast::IteratorType::kWhile); }
;
ClosedStatement
: "if" SimpleExpression "then" ClosedStatement "else" ClosedStatement { \
$$ = ast::action::MakeStatement<ast::Branch>({$2, $4, $6}, @1, ast::BranchType::kIf); \
}
| "while" SimpleExpression "do" ClosedStatement { $$ = ast::action::MakeStatement<ast::Iterator>({$2, $4}, @1, ast::IteratorType::kWhile); }
| NonIfStatement
;
This is the bison output
State 148
42 ConditionStmt: ClosedStatement .
45 OpenStatement: "if" SimpleExpression "then" ClosedStatement . "else" OpenStatement
47 ClosedStatement: "if" SimpleExpression "then" ClosedStatement . "else" ClosedStatement
"else" shift, and go to state 158
"else" [reduce using rule 42 (ConditionStmt)]
$default reduce using rule 42 (ConditionStmt)
State 158
45 OpenStatement: "if" SimpleExpression "then" ClosedStatement "else" . OpenStatement
47 ClosedStatement: "if" SimpleExpression "then" ClosedStatement "else" . ClosedStatement
"if" shift, and go to state 61
"return" shift, and go to state 62
"for" shift, and go to state 63
"while" shift, and go to state 64
"break" shift, and go to state 65
"not" shift, and go to state 36
";" shift, and go to state 66
"{" shift, and go to state 67
"(" shift, and go to state 37
"-" shift, and go to state 38
"*" shift, and go to state 39
"?" shift, and go to state 40
kNumericConst shift, and go to state 41
kCharConst shift, and go to state 42
kString shift, and go to state 43
kIdentifier shift, and go to state 44
kBoolConst shift, and go to state 45
NonIfStatement go to state 69
ExpressionStmt go to state 70
CompoundStmt go to state 71
OpenStatement go to state 163
ClosedStatement go to state 164
IteratorStmt go to state 75
ReturnStmt go to state 76
BreakStmt go to state 77
Expression go to state 78
SimpleExpression go to state 79
AndExpr go to state 47
UnaryReletiveExpr go to state 48
ReletiveExpr go to state 49
SumExpr go to state 50
MulExp go to state 51
UnaryExpr go to state 52
UnaryOper go to state 53
Factor go to state 54
Mutable go to state 80
Immutable go to state 56
Call go to state 57
Constant go to state 58
These two lines in the bison .output file
"else" shift, and go to state 158
"else" [reduce using rule 42 (ConditionStmt)]
tell you that the shift-reduce conflict is between shifting an else and reducing to the non-terminal ConditionStmt. This tells you that the problem is somewhere you have ConditionStmt on the right-hand-side of a rule -- something about that context allows the ConditionStmt to be followed by an else. But in the grammar you show, ConditionStmt is never used, so we can't say what that problem is.
My best guess is that you have something in the rule for NonIfStatement (which you also don't show) that ends (directly or indirectly) with ConditionStmt on the rhs, which causes this problem.