ImportValue cannot be used inside the Conditions section (#696)

src/cfnlint/rules/functions/ImportValue.py

@@ -45,9 +45,17 @@ def match(self, cfn):
             'Ref'
         ]
 
+        unsupported_locations = [
+            'Conditions'
+        ]
+
         for iv_obj in iv_objs:
             iv_value = iv_obj[-1]
             tree = iv_obj[:-1]
+            if iv_obj[0] in unsupported_locations:
+                message = 'ImportValue cannot be used inside {0} at {1}'
+                matches.append(RuleMatch(
+                    tree, message.format(iv_obj[0], '/'.join(map(str, tree[:-1])))))
             if isinstance(iv_value, dict):
                 if len(iv_value) == 1:
                     for key, _ in iv_value.items():

test/fixtures/templates/bad/functions/import_value.yaml

@@ -0,0 +1,14 @@
+---
+AWSTemplateFormatVersion: "2010-09-09"
+Conditions:
+  primaryRegion: !Equals [!Ref 'AWS::Region', !ImportValue PrimaryRegion]
+Resources:
+  subnet:
+    Type: AWS::EC2::Subnet
+    Properties:
+      CidrBlock:
+        Fn::ImportValue:
+          Fn::ImportValue: CidrBlock
+      VpcId:
+        Fn::ImportValue:
+        - PrimaryRegion

test/rules/functions/test_import_value.py

@@ -0,0 +1,34 @@
+"""
+  Copyright 2019 Amazon.com, Inc. or its affiliates. All Rights Reserved.
+
+  Permission is hereby granted, free of charge, to any person obtaining a copy of this
+  software and associated documentation files (the "Software"), to deal in the Software
+  without restriction, including without limitation the rights to use, copy, modify,
+  merge, publish, distribute, sublicense, and/or sell copies of the Software, and to
+  permit persons to whom the Software is furnished to do so.
+
+  THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED,
+  INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A
+  PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT
+  HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
+  OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE
+  SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+"""
+from cfnlint.rules.functions.ImportValue import ImportValue  # pylint: disable=E0401
+from .. import BaseRuleTestCase
+
+
+class TestImportValue(BaseRuleTestCase):
+    """Test Rules Get Att """
+    def setUp(self):
+        """Setup"""
+        super(TestImportValue, self).setUp()
+        self.collection.register(ImportValue())
+
+    def test_file_positive(self):
+        """Test Positive"""
+        self.helper_file_positive()
+
+    def test_file_negative(self):
+        """Test failure"""
+        self.helper_file_negative('test/fixtures/templates/bad/functions/import_value.yaml', 3)