simplify parse error reporting

since nix doesn't use the bison `error` terminal anywhere any invocation
of yyerror will immediately cause a failure. since we're *already*
leaking tons of memory whatever little bit bison allocates internally
doesn't much matter any more, and we'll be replacing the parser soon anyway.

coincidentally this now also matches the error behavior of URIs when
they are disabled or ~/ paths in pure eval mode, duplicate attr
detection etc.

(cherry picked from commit e8d9de967fe47a7f9324b0022a2ef50df59f419d)
Change-Id: I560c50d11dceddc2d7cf9ed2c6c631a309ce574e

1 files changed, 6 insertions, 7 deletions

diff --git a/src/libexpr/parser.y b/src/libexpr/parser.y
index 425ff16c1..0c6952929 100644
--- a/src/libexpr/parser.y
+++ b/src/libexpr/parser.y
@@ -18,6 +18,7 @@
 
 #include <variant>
 
+#include "finally.hh"
 #include "util.hh"
 
 #include "nixexpr.hh"
@@ -59,7 +60,6 @@ namespace nix {
         Expr * result;
         SourcePath basePath;
         PosTable::Origin origin;
-        std::optional<ErrorInfo> error;
     };
 
 }
@@ -314,10 +314,10 @@ static inline PosIdx makeCurPos(const YYLTYPE & loc, ParseData * data)
 
 void yyerror(YYLTYPE * loc, yyscan_t scanner, ParseData * data, const char * error)
 {
-    data->error = {
+    throw ParseError({
         .msg = hintfmt(error),
         .errPos = data->state.positions[makeCurPos(*loc, data)]
-    };
+    });
 }
 
 
@@ -685,11 +685,10 @@ Expr * EvalState::parse(
     };
 
     yylex_init(&scanner);
-    yy_scan_buffer(text, length, scanner);
-    int res = yyparse(scanner, &data);
-    yylex_destroy(scanner);
+    Finally _destroy([&] { yylex_destroy(scanner); });
 
-    if (res) throw ParseError(data.error.value());
+    yy_scan_buffer(text, length, scanner);
+    yyparse(scanner, &data);
 
     data.result->bindVars(*this, staticEnv);