Fix a bug with named NEVER_MATCH expressions

CHANGELOG.md

@@ -16,6 +16,7 @@ Released: TBD
 
 ### Minor Changes
 
+- [#454](https://github.com/peggyjs/peggy/pull/454) Fix a bug with named NEVER_MATCH expressions
 - [#453](https://github.com/peggyjs/peggy/pull/453) Make generate-bytecode.js ts-clean
 - [#452](https://github.com/peggyjs/peggy/pull/452) Fixes to prepare generate-bytecode.js for ts-check
 - [#432](https://github.com/peggyjs/peggy/pull/432) Add peggy.code-workspace

docs/js/examples.js

@@ -204,7 +204,6 @@ function peg$parse(input, options) {
   var peg$e11 = peg$literalExpectation(" ", false);
   var peg$e12 = peg$literalExpectation("c", false);
   var peg$e13 = peg$classExpectation([["a", "c"]], false, false);
-  var peg$e14 = peg$otherExpectation("The rest of the input");
 
   var peg$f0 = function(match, rest) { return {match, rest}; };
   var peg$f1 = function(match, rest) { return {match, rest}; };
@@ -1488,8 +1487,6 @@ function peg$parse(input, options) {
     }
     s0 = input.substring(s0, peg$currPos);
     peg$silentFails--;
-    s1 = peg$FAILED;
-    if (peg$silentFails === 0) { peg$fail(peg$e14); }
 
     return s0;
   }

lib/compiler/passes/generate-bytecode.js

@@ -715,8 +715,8 @@ function generateBytecode(ast, options) {
 
     named(node, context) {
       const match = node.match || 0;
-      // Expectation not required if node always fail
-      const nameIndex = (match === NEVER_MATCH)
+      // Expectation not required if node always match
+      const nameIndex = (match === ALWAYS_MATCH)
         ? -1
         : addExpectedConst({ type: "rule", value: node.name });
 
@@ -728,7 +728,7 @@ function generateBytecode(ast, options) {
         [op.SILENT_FAILS_ON],
         generate(node.expression, context),
         [op.SILENT_FAILS_OFF],
-        buildCondition(match, [op.IF_ERROR], [op.FAIL, nameIndex], [])
+        buildCondition(-match, [op.IF_ERROR], [op.FAIL, nameIndex], [])
       );
     },
 

test/behavior/generated-parser-behavior.spec.js

@@ -215,11 +215,11 @@ describe("generated parser behavior", () => {
             });
           });
 
-          it("reports match failure and doesn't records any expectations when expression never match", () => {
+          it("reports match failure and records an expectation of type \"other\" when expression never match", () => {
             const parser = peg.generate("start 'start' = []", options);
 
             expect(parser).to.failToParse("b", {
-              expected: [],
+              expected: [{ type:"other", description: "start" }],
             });
           });