I'm writing a parser using ANTLR and am now at the stage of testing my parser/lexer. I stumbled over a strange bug while trying to parse basically a variable assignment. (Like this)
Foo = mpsga(LT);
I get the error : mismatched input 'line 1:6 mismatched input 'mpsga(LT)' expecting 'mpsga'
This is especially strange for when I remove the brackets (or the argument LT
), the parser recognizes mpsga
and it only misses the brackets (or the argument).
My Grammar looks something like this:
lexer grammar FooLexer;
COMMENT
:
'#' ~[\r\n]* -> channel ( HIDDEN )
;
NEWLINE
:
(
'\r'? '\n'
| '\r'
)+ -> channel ( HIDDEN )
;
EQUALSSIGN
:
'='
;
SEMICOLON
:
';'
;
MPSGA_255_1
:
'LT'
;
MPSGA
:
'mpsga'
;
WHITESPACE
:
(
' '
| '\t'
)+ -> channel ( HIDDEN )
;
BRACKET_OPEN
:
'('
;
BRACKET_CLOSED
:
')'
;
VAR
:
[a-zA-Z][0-9a-zA-Z_]*
;
parser grammar FooParser;
options {
tokenVocab = FooLexer;
}
stmt_block
:
stmt_list EOF
;
stmt
:
VAR EQUALSSIGN expr SEMICOLON NEWLINE?
;
stmt_list
:
stmt
| stmt_list stmt
;
expr
:
extvar
;
extvar
:
MPSGA BRACKET_OPEN mpsga_field BRACKET_CLOSED
;
mpsga_field
:
MPSGA_255_1
;
When I try to parse this Foo = mpsga(LT);
in Java i get the error. Any help is appreciated!
My Parse hierachy looks like the following:
Foo = mpsga(LT);
stmt_block
->stmt_list:1
-->stmt
--->"Foo"
--->"="
--->expr
---->extvar
----->"mpsga(LT)"
---->";"
-><EOF>
Foo = mpsga(LT;
stmt_block
->stmt_list:1
-->stmt
--->"Foo"
--->"="
--->expr
---->extvar
----->"mpsga"
----->"("
----->mpsga_field
------>"LT"
----->"<missing ')'>"
---->";"
-><EOF>
DISCLAIMER: I solved the problem. For anyone experiencing the same issue: I had some Lexer rules that were ambiguous for the mpsga
part.
这是论点:你的语法接受'foo'或'foo2'作为常量,而不是some_foo。
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