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Resolve shift/reduce conflict of 'def' vs '|'

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This was an important conflict. In the following expression:

    def a: 0; . | a

Bison needs to decide between these two equally valid
parses:

    (def a: 0; .) | a
    def a: 0; (. | a)

For jq we want the second one, because the first results in
"a/0 is not defined". In the current parser the first parse
is a reduce and the second parse is a shift. Since Bison
prefers to shift in shift/reduce conflicts, we accidentally
got the correct behavior.

This commit adds a precedence level FUNCDEF which is lower
precedence than '|', meaning we explicitly choose the
correct parse.

Of course many unit tests already cover this case, but I
added one specifically for it.
This commit is contained in:
David Tolnay
2015-07-18 21:57:20 -07:00
parent 1628bbf95f
commit 66ef8e2c24
4 changed files with 825 additions and 834 deletions
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1643
parser.c
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File diff suppressed because it is too large Load Diff

6
parser.h
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@@ -105,7 +105,8 @@ struct lexer_param;
QQSTRING_TEXT = 296, QQSTRING_TEXT = 296,
QQSTRING_INTERP_START = 297, QQSTRING_INTERP_START = 297,
QQSTRING_INTERP_END = 298, QQSTRING_INTERP_END = 298,
QQSTRING_END = 299 QQSTRING_END = 299,
FUNCDEF = 300
}; };
#endif #endif
/* Tokens. */ /* Tokens. */
@@ -151,6 +152,7 @@ struct lexer_param;
#define QQSTRING_INTERP_START 297 #define QQSTRING_INTERP_START 297
#define QQSTRING_INTERP_END 298 #define QQSTRING_INTERP_END 298
#define QQSTRING_END 299 #define QQSTRING_END 299
#define FUNCDEF 300
/* Value type. */ /* Value type. */
#if ! defined YYSTYPE && ! defined YYSTYPE_IS_DECLARED #if ! defined YYSTYPE && ! defined YYSTYPE_IS_DECLARED
@@ -162,7 +164,7 @@ union YYSTYPE
jv literal; jv literal;
block blk; block blk;
#line 166 "parser.h" /* yacc.c:1909 */ #line 168 "parser.h" /* yacc.c:1909 */
}; };
# define YYSTYPE_IS_TRIVIAL 1 # define YYSTYPE_IS_TRIVIAL 1
# define YYSTYPE_IS_DECLARED 1 # define YYSTYPE_IS_DECLARED 1

5
parser.y
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@@ -91,8 +91,9 @@ struct lexer_param;
%token QQSTRING_END %token QQSTRING_END
/* see Exp '?' rule */ /* see Exp '?' rule */
%expect 34 %expect 9
%precedence FUNCDEF
%right '|' %right '|'
%left ',' %left ','
%right "//" %right "//"
@@ -306,7 +307,7 @@ FuncDef FuncDefs {
} }
Exp: Exp:
FuncDef Exp %prec ';' { FuncDef Exp %prec FUNCDEF {
$$ = block_bind_referenced($1, $2, OP_IS_CALL_PSEUDO); $$ = block_bind_referenced($1, $2, OP_IS_CALL_PSEUDO);
} | } |

5
tests/jq.test
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@@ -553,6 +553,11 @@ def f(a;b;c;d;e;f): [a+1,b,c,d,e,f]; f(.[0];.[1];.[0];.[0];.[0];.[0])
[1,2] [1,2]
[2,2,1,1,1,1] [2,2,1,1,1,1]
# Test precedence of 'def' vs '|'
def a: 0; . | a
null
0
# Many arguments # Many arguments
def f(a;b;c;d;e;f;g;h;i;j): [j,i,h,g,f,e,d,c,b,a]; f(.[0];.[1];.[2];.[3];.[4];.[5];.[6];.[7];.[8];.[9]) def f(a;b;c;d;e;f;g;h;i;j): [j,i,h,g,f,e,d,c,b,a]; f(.[0];.[1];.[2];.[3];.[4];.[5];.[6];.[7];.[8];.[9])
[0,1,2,3,4,5,6,7,8,9] [0,1,2,3,4,5,6,7,8,9]