Display other locations of Reused lint errors

Summary: It's not trivial to find them inside 700+ lines long functions.

Test Plan:
Linted `reused-iterators.lint-test` renamed to `_.php`, saw other locations.
Repeated for `reused-local.lint-test`.
Repeated for `duplicate-key-in-array.lint-test`.

Reviewers: epriestley

Reviewed By: epriestley

CC: aran, Korvin

Differential Revision: https://secure.phabricator.com/D4871

src/lint/linter/ArcanistLinter.php

@@ -42,6 +42,22 @@ abstract class ArcanistLinter {
     return $this->activePath;
   }
 
+  public function getOtherLocation($offset, $path = null) {
+    if ($path === null) {
+      $path = $this->getActivePath();
+    }
+
+    list($line, $char) = $this->getEngine()->getLineAndCharFromOffset(
+      $path,
+      $offset);
+
+    return array(
+      'path' => $path,
+      'line' => $line + 1,
+      'char' => $char,
+    );
+  }
+
   public function stopAllLinters() {
     $this->stopAllLinters = true;
     return $this;

src/lint/linter/ArcanistXHPASTLinter.php

@@ -787,7 +787,8 @@ final class ArcanistXHPASTLinter extends ArcanistBaseXHPASTLinter {
       $bin_exprs = $for_expr->selectDescendantsOfType('n_BINARY_EXPRESSION');
       foreach ($bin_exprs as $bin_expr) {
         if ($bin_expr->getChildByIndex(1)->getConcreteString() == '=') {
-          $var_map[$bin_expr->getChildByIndex(0)->getConcreteString()] = true;
+          $var = $bin_expr->getChildByIndex(0);
+          $var_map[$var->getConcreteString()] = $var;
         }
       }
 
@@ -812,7 +813,7 @@ final class ArcanistXHPASTLinter extends ArcanistBaseXHPASTLinter {
         }
         $name = $var->getConcreteString();
         $name = trim($name, '&'); // Get rid of ref silliness.
-        $var_map[$name] = true;
+        $var_map[$name] = $var;
       }
 
       $used_vars[$foreach_loop->getID()] = $var_map;
@@ -830,12 +831,18 @@ final class ArcanistXHPASTLinter extends ArcanistBaseXHPASTLinter {
         $shared = array_intersect_key($outer_vars, $inner_vars);
         if ($shared) {
           $shared_desc = implode(', ', array_keys($shared));
-          $this->raiseLintAtNode(
+          $message = $this->raiseLintAtNode(
             $inner_loop->getChildByIndex(0),
             self::LINT_REUSED_ITERATORS,
             "This loop reuses iterator variables ({$shared_desc}) from an ".
             "outer loop. You might be clobbering the outer iterator. Change ".
             "the inner loop to use a different iterator name.");
+
+          $locations = array();
+          foreach ($shared as $var) {
+            $locations[] = $this->getOtherLocation($var->getOffset());
+          }
+          $message->setOtherLocations($locations);
         }
       }
     }
@@ -1129,12 +1136,16 @@ final class ArcanistXHPASTLinter extends ArcanistBaseXHPASTLinter {
           if ($declarations[$concrete] < $offset) {
             if (!empty($uses[$concrete]) &&
                 max($uses[$concrete]) > $offset) {
-              $this->raiseLintAtNode(
+              $message = $this->raiseLintAtNode(
                 $var,
                 self::LINT_REUSED_AS_ITERATOR,
                 'This iterator variable is a previously declared local '.
                 'variable. To avoid overwriting locals, do not reuse them '.
                 'as iterator variables.');
+              $message->setOtherLocations(array(
+                $this->getOtherLocation($declarations[$concrete]),
+                $this->getOtherLocation(max($uses[$concrete])),
+              ));
             }
           }
         }
@@ -1930,13 +1941,18 @@ final class ArcanistXHPASTLinter extends ArcanistBaseXHPASTLinter {
       }
 
       foreach ($keys_warn as $key => $_) {
-        foreach ($nodes_by_key[$key] as $node) {
-          $this->raiseLintAtNode(
-            $node,
-            self::LINT_DUPLICATE_KEYS_IN_ARRAY,
-            "Duplicate key in array initializer. PHP will ignore all ".
+        $node = array_pop($nodes_by_key[$key]);
+        $message = $this->raiseLintAtNode(
+          $node,
+          self::LINT_DUPLICATE_KEYS_IN_ARRAY,
+          "Duplicate key in array initializer. PHP will ignore all ".
             "but the last entry.");
+
+        $locations = array();
+        foreach ($nodes_by_key[$key] as $node) {
+          $locations[] = $this->getOtherLocation($node->getOffset());
         }
+        $message->setOtherLocations($locations);
       }
     }
   }

src/lint/linter/__tests__/xhpast/duplicate-key-in-array.lint-test

@@ -34,16 +34,9 @@ $f = array(
   $a => 'var2',
 );
 ~~~~~~~~~~
-error:3:3
 error:5:3
-error:6:3
-error:7:3
 error:8:3
-error:14:3
 error:15:3
-error:19:3
 error:20:3
-error:24:3
 error:25:3
-error:32:3
 error:34:3