highlight assignments as 'with' statement target as error (PY-7529)

python/psi-api/src/com/jetbrains/python/psi/PyElementVisitor.java

@@ -257,4 +257,8 @@ public class PyElementVisitor extends PsiElementVisitor {
   public void visitPyKeywordArgument(PyKeywordArgument node) {
     visitPyElement(node);
   }
+
+  public void visitPyWithItem(PyWithItem node) {
+    visitPyElement(node);
+  }
 }

python/src/com/jetbrains/python/psi/impl/PyWithItemImpl.java

@@ -3,6 +3,7 @@ package com.jetbrains.python.psi.impl;
 import com.intellij.lang.ASTNode;
 import com.intellij.psi.PsiElement;
 import com.jetbrains.python.PyTokenTypes;
+import com.jetbrains.python.psi.PyElementVisitor;
 import com.jetbrains.python.psi.PyExpression;
 import com.jetbrains.python.psi.PyWithItem;
 
@@ -14,6 +15,11 @@ public class PyWithItemImpl extends PyElementImpl implements PyWithItem {
     super(astNode);
   }
 
+  @Override
+  protected void acceptPyVisitor(PyElementVisitor pyVisitor) {
+    pyVisitor.visitPyWithItem(this);
+  }
+
   @Override
   public PyExpression getExpression() {
     ASTNode[] children = getNode().getChildren(null);

python/src/com/jetbrains/python/validation/AssignTargetAnnotator.java

@@ -12,7 +12,7 @@ import static com.jetbrains.python.PyBundle.message;
  */
 public class AssignTargetAnnotator extends PyAnnotator {
   private enum Operation {
-    Assign, AugAssign, Delete, Except, For
+    Assign, AugAssign, Delete, Except, For, With
   }
 
   @Override
@@ -51,6 +51,14 @@ public class AssignTargetAnnotator extends PyAnnotator {
     }
   }
 
+  @Override
+  public void visitPyWithItem(PyWithItem node) {
+    PyExpression target = node.getTarget();
+    if (target != null) {
+      target.accept(new ExprVisitor(Operation.With));
+    }
+  }
+
   private class ExprVisitor extends PyElementVisitor {
     private final Operation myOp;
     private final String DELETING_NONE = message("ANN.deleting.none");

python/testData/highlighting/assignmentTargetWith.py

@@ -0,0 +1,2 @@
+with open("") as <error descr="can't assign to operator">my_<<var</error>:
+    pass

python/testSrc/com/jetbrains/python/PythonHighlightingTest.java

@@ -65,6 +65,11 @@ public class PythonHighlightingTest extends PyTestCase {
     doTest(true, false);
   }
 
+  public void testAssignmentTargetWith() {  // PY-7529
+    setLanguageLevel(LanguageLevel.PYTHON27);
+    doTest(true, false);
+  }
+
   public void testAssignmentTargets3K() {
     doTest(LanguageLevel.PYTHON30, true, false);    
   }