From 3f31775252c9b73f73912cfe23a4ccd124f9eee0 Mon Sep 17 00:00:00 2001
From: Tom Hvitved <hvitved@github.com>
Date: Mon, 18 Jan 2021 15:01:41 +0100
Subject: [PATCH 1/2] CFG: Add test for constant condition

---
 .../controlflow/graph/Cfg.expected            | 35 ++++++++++++++++++-
 .../library-tests/controlflow/graph/ifs.rb    |  6 ++++
 2 files changed, 40 insertions(+), 1 deletion(-)

diff --git a/ql/test/library-tests/controlflow/graph/Cfg.expected b/ql/test/library-tests/controlflow/graph/Cfg.expected
index 8c8ea06a75c..ad514265c5e 100644
--- a/ql/test/library-tests/controlflow/graph/Cfg.expected
+++ b/ql/test/library-tests/controlflow/graph/Cfg.expected
@@ -103,6 +103,9 @@ ifs.rb:
 #   36| enter conditional_method_def
 #-----|  -> puts
 
+#   40| enter constant_condition
+#-----|  -> true
+
 loops.rb:
 #    1| enter top-level
 #-----|  -> m1
@@ -2440,7 +2443,7 @@ ifs.rb:
 #-----|  -> If
 
 #   36| UnlessModifier
-#-----|  -> exit top-level (normal)
+#-----|  -> constant_condition
 
 #   36| Method
 #-----|  -> UnlessModifier
@@ -2467,6 +2470,31 @@ ifs.rb:
 #   38| 2
 #-----|  -> Binary
 
+#   40| Method
+#-----|  -> exit top-level (normal)
+
+#   40| constant_condition
+#-----|  -> Method
+
+#   41| If
+#-----|  -> exit constant_condition (normal)
+
+#   41| Unary
+#-----| false -> If
+#-----| true -> puts
+
+#   41| true
+#-----| false -> Unary
+
+#   42| Call
+#-----|  -> If
+
+#   42| puts
+#-----|  -> String
+
+#   42| String
+#-----|  -> Call
+
 loops.rb:
 #    1| Method
 #-----|  -> m2
@@ -3771,6 +3799,8 @@ ifs.rb:
 
 #   36| exit conditional_method_def
 
+#   40| exit constant_condition
+
 loops.rb:
 #    1| exit top-level
 
@@ -3926,6 +3956,9 @@ ifs.rb:
 #   36| exit conditional_method_def (normal)
 #-----|  -> exit conditional_method_def
 
+#   40| exit constant_condition (normal)
+#-----|  -> exit constant_condition
+
 loops.rb:
 #    1| exit top-level (normal)
 #-----|  -> exit top-level
diff --git a/ql/test/library-tests/controlflow/graph/ifs.rb b/ql/test/library-tests/controlflow/graph/ifs.rb
index a774f1e8ca6..aa8ac8a342b 100644
--- a/ql/test/library-tests/controlflow/graph/ifs.rb
+++ b/ql/test/library-tests/controlflow/graph/ifs.rb
@@ -36,3 +36,9 @@ end
 def conditional_method_def()
   puts "bla"
 end unless 1 == 2
+
+def constant_condition()
+  if !true
+    puts "Impossible"
+  end
+end

From 34fe416a8504b7715d53def6497ef59e60947af2 Mon Sep 17 00:00:00 2001
From: Tom Hvitved <hvitved@github.com>
Date: Mon, 18 Jan 2021 15:03:58 +0100
Subject: [PATCH 2/2] CFG: Fix bug in `LogicalNotTree`

---
 .../controlflow/internal/ControlFlowGraphImpl.qll  |  8 ++------
 .../library-tests/controlflow/graph/Cfg.expected   | 14 ++------------
 2 files changed, 4 insertions(+), 18 deletions(-)

diff --git a/ql/src/codeql_ruby/controlflow/internal/ControlFlowGraphImpl.qll b/ql/src/codeql_ruby/controlflow/internal/ControlFlowGraphImpl.qll
index 759c710f2d0..39a62fcee08 100644
--- a/ql/src/codeql_ruby/controlflow/internal/ControlFlowGraphImpl.qll
+++ b/ql/src/codeql_ruby/controlflow/internal/ControlFlowGraphImpl.qll
@@ -782,12 +782,8 @@ module Trees {
 
     final override predicate succ(AstNode pred, AstNode succ, Completion c) {
       succ = this and
-      (
-        last(operand, pred, c.(BooleanCompletion).getDual())
-        or
-        last(operand, pred, c) and
-        c instanceof SimpleCompletion
-      )
+      last(operand, pred, c) and
+      c instanceof NormalCompletion
     }
   }
 
diff --git a/ql/test/library-tests/controlflow/graph/Cfg.expected b/ql/test/library-tests/controlflow/graph/Cfg.expected
index ad514265c5e..43788edcec7 100644
--- a/ql/test/library-tests/controlflow/graph/Cfg.expected
+++ b/ql/test/library-tests/controlflow/graph/Cfg.expected
@@ -2479,21 +2479,11 @@ ifs.rb:
 #   41| If
 #-----|  -> exit constant_condition (normal)
 
-#   41| Unary
+#   41| [false] Unary
 #-----| false -> If
-#-----| true -> puts
 
 #   41| true
-#-----| false -> Unary
-
-#   42| Call
-#-----|  -> If
-
-#   42| puts
-#-----|  -> String
-
-#   42| String
-#-----|  -> Call
+#-----| true -> [false] Unary
 
 loops.rb:
 #    1| Method