Code review nits from peggyjs#300

CHANGELOG.md

@@ -6,9 +6,6 @@ This file documents all notable changes to Peggy.
 Unreleased
 ----------
 
-- [#299](https://github.com/peggyjs/peggy/issues/299) Add example grammar for a
-  [SemVer.org](https://semver.org) semantic version string
-
 Released: TBD
 
 ### Major Changes
@@ -37,6 +34,8 @@ Released: TBD
   (can be useful for plugin writers), from @Mingun
 - [#294](https://github.com/peggyjs/peggy/pull/294) Website: show errors in the
   editors, from @Mingun
+- [#299](https://github.com/peggyjs/peggy/issues/299) Add example grammar for a
+  [SemVer.org](https://semver.org) semantic version string, from @dselman
 
 ### Bug Fixes
 

examples/semver.peggy

@@ -3,33 +3,27 @@
  * https://semver.org/spec/v2.0.0.html
  * For unit tests see: https://github.com/dselman/peggy-semver
  */
+
 semver
   = versionCore:versionCore
     pre:('-' @preRelease)?
     build:('+' @build)?
   {
-    return { versionCore, pre, build };
+    return { ...versionCore, pre, build };
   }
 
 versionCore
-  = major:$numericIdentifier '.' minor:$numericIdentifier '.' patch:$numericIdentifier
-  {
-    return {
-      major: parseInt(major, 10),
-      minor: parseInt(minor, 10),
-      patch: parseInt(patch, 10),
-    };
+  = major:numericIdentifier '.' minor:numericIdentifier '.' patch:numericIdentifier {
+    return { major, minor, patch };
   }
 
 preRelease
-  = head:$preReleaseIdentifier tail:('.' @$preReleaseIdentifier)*
-  {
+  = head:preReleaseIdentifier tail:('.' @preReleaseIdentifier)* {
     return [head, ...tail];
   }
 
 build
-  = head:$buildIdentifier tail:('.' @$buildIdentifier)*
-  {
+  = head:buildIdentifier tail:('.' @buildIdentifier)* {
     return [head, ...tail];
   }
 
@@ -39,13 +33,17 @@ preReleaseIdentifier
 
 buildIdentifier
   = alphanumericIdentifier
-  / digit+
+  / $digit+ // Not a number, buildIdentifiers aren't semantically significant.
 
+// If there is a non-digit anywhere, this label is alphanumeric, and
+// is compared lexically.  Return a string.
 alphanumericIdentifier
-  = digit* nonDigit identifierChar*
+  = $(digit* nonDigit identifierChar*)
 
+// Any semantically significant numbers are turned into integers for
+// later numeric comparison.
 numericIdentifier
-  = '0' / (positiveDigit digit*)
+  = n:('0' / $(positiveDigit digit*)) { return parseInt(n, 10); }
 
 identifierChar
   = [a-z0-9-]i
@@ -57,4 +55,4 @@ digit
   = [0-9]
 
 positiveDigit
-  = [1-9]
+  = [1-9]