[[FIX]] Close synthetic scope for labeled blocks

JSHint creates a synthetic block scope in order to track labeled
statements prior to parsing the statements themselves. Previously, this
scope was not closed (or "unstacked") for labeled Block statements.

Ensure that the synthetic scope is closed in these cases as well. Assert
correct behavior via various parsing/linting mechanisms that are aware
of scope.

src/jshint.js

@@ -1622,6 +1622,11 @@ var JSHINT = (function() {
       //  }
       var iscase = (state.funct["(verb)"] === "case" && state.tokens.curr.value === ":");
       block(true, true, false, false, iscase);
+
+      if (hasOwnScope) {
+        state.funct["(scope)"].unstack();
+      }
+
       return;
     }
 

tests/unit/core.js

@@ -866,6 +866,14 @@ exports.testES6Modules = function (test) {
   TestRun(test)
     .test(src2, {});
 
+  // See gh-3055 "Labels Break JSHint"
+  TestRun(test, "following labeled block")
+    .test([
+      "label: {}",
+      "export function afterLabelExported() {}",
+      "import afterLabelImported from 'elsewhere';"
+    ], { esversion: 6 });
+
   test.done();
 };
 
@@ -1756,6 +1764,14 @@ exports.labelsOutOfScope = function (test) {
     .addError(24, "'baz' is not a statement label.")
     .test(src);
 
+  // See gh-3055 "Labels Break JSHint"
+  TestRun(test, "following labeled block")
+    .addError(2, "'x' is not a statement label.")
+    .test([
+      "x: {}",
+      "break x;"
+    ]);
+
   test.done();
 };
 

tests/unit/options.js

@@ -794,6 +794,16 @@ exports.undef = function (test) {
 
   test.strictEqual(JSHINT.data().implieds, undefined);
 
+  // See gh-3055 "Labels Break JSHint"
+  TestRun(test, "following labeled block")
+    .addError(4, "'x' is not defined.")
+    .test([
+      "label: {",
+      "  let x;",
+      "}",
+      "void x;"
+    ], { esversion: 6, undef: true });
+
   test.done();
 };