C#: Make SuppressNullableWarningExpr a nonNullValue, and add a test.

Author: calumgrant

csharp/ql/src/semmle/code/csharp/controlflow/Guards.qll

@@ -673,6 +673,8 @@ module Internal {
     or
     e.(Call).getTarget().getSourceDeclaration() instanceof NonNullCallable and
     not e.(QualifiableExpr).isConditional()
+    or
+    e instanceof SuppressNullableWarningExpr
   }
 
   /** Holds if expression `e2` is a non-`null` value whenever `e1` is. */

csharp/ql/test/library-tests/csharp8/NullableRefTypes.cs

@@ -7,5 +7,7 @@ void TestNullableRefTypes()
         string? x = "source";
         string y = x!;
         y = x!!;
+        x = null;
+        y = x!;
     }
 }

csharp/ql/test/library-tests/csharp8/NullableRefTypes.expected

@@ -2,25 +2,46 @@ suppressNullableWarnings
 | NullableRefTypes.cs:8:20:8:21 | ...! | NullableRefTypes.cs:8:20:8:20 | access to local variable x |
 | NullableRefTypes.cs:9:13:9:14 | ...! | NullableRefTypes.cs:9:13:9:13 | access to local variable x |
 | NullableRefTypes.cs:9:13:9:15 | ...! | NullableRefTypes.cs:9:13:9:14 | ...! |
+| NullableRefTypes.cs:11:13:11:14 | ...! | NullableRefTypes.cs:11:13:11:13 | access to local variable x |
 nullableDataFlow
 | NullableRefTypes.cs:7:17:7:28 | SSA def(x) | NullableRefTypes.cs:8:20:8:20 | access to local variable x |
 | NullableRefTypes.cs:7:21:7:28 | "source" | NullableRefTypes.cs:7:17:7:28 | SSA def(x) |
 | NullableRefTypes.cs:8:20:8:20 | access to local variable x | NullableRefTypes.cs:8:20:8:21 | ...! |
 | NullableRefTypes.cs:8:20:8:20 | access to local variable x | NullableRefTypes.cs:9:13:9:13 | access to local variable x |
 | NullableRefTypes.cs:9:13:9:13 | access to local variable x | NullableRefTypes.cs:9:13:9:14 | ...! |
 | NullableRefTypes.cs:9:13:9:14 | ...! | NullableRefTypes.cs:9:13:9:15 | ...! |
+| NullableRefTypes.cs:10:9:10:16 | SSA def(x) | NullableRefTypes.cs:11:13:11:13 | access to local variable x |
+| NullableRefTypes.cs:10:13:10:16 | null | NullableRefTypes.cs:10:9:10:16 | SSA def(x) |
+| NullableRefTypes.cs:11:13:11:13 | access to local variable x | NullableRefTypes.cs:11:13:11:14 | ...! |
 nullableControlFlow
-| NullableRefTypes.cs:5:10:5:29 | enter TestNullableRefTypes | NullableRefTypes.cs:6:5:10:5 | {...} | successor |
-| NullableRefTypes.cs:6:5:10:5 | {...} | NullableRefTypes.cs:7:9:7:29 | ... ...; | successor |
+| NullableRefTypes.cs:5:10:5:29 | enter TestNullableRefTypes | NullableRefTypes.cs:6:5:12:5 | {...} | successor |
+| NullableRefTypes.cs:6:5:12:5 | {...} | NullableRefTypes.cs:7:9:7:29 | ... ...; | successor |
 | NullableRefTypes.cs:7:9:7:29 | ... ...; | NullableRefTypes.cs:7:21:7:28 | "source" | successor |
 | NullableRefTypes.cs:7:17:7:28 | String x = ... | NullableRefTypes.cs:8:9:8:22 | ... ...; | successor |
 | NullableRefTypes.cs:7:21:7:28 | "source" | NullableRefTypes.cs:7:17:7:28 | String x = ... | successor |
 | NullableRefTypes.cs:8:9:8:22 | ... ...; | NullableRefTypes.cs:8:20:8:20 | access to local variable x | successor |
 | NullableRefTypes.cs:8:16:8:21 | String y = ... | NullableRefTypes.cs:9:9:9:16 | ...; | successor |
 | NullableRefTypes.cs:8:20:8:20 | access to local variable x | NullableRefTypes.cs:8:20:8:21 | ...! | successor |
 | NullableRefTypes.cs:8:20:8:21 | ...! | NullableRefTypes.cs:8:16:8:21 | String y = ... | successor |
-| NullableRefTypes.cs:9:9:9:15 | ... = ... | NullableRefTypes.cs:5:10:5:29 | exit TestNullableRefTypes | successor |
+| NullableRefTypes.cs:9:9:9:15 | ... = ... | NullableRefTypes.cs:10:9:10:17 | ...; | successor |
 | NullableRefTypes.cs:9:9:9:16 | ...; | NullableRefTypes.cs:9:13:9:13 | access to local variable x | successor |
 | NullableRefTypes.cs:9:13:9:13 | access to local variable x | NullableRefTypes.cs:9:13:9:14 | ...! | successor |
 | NullableRefTypes.cs:9:13:9:14 | ...! | NullableRefTypes.cs:9:13:9:15 | ...! | successor |
 | NullableRefTypes.cs:9:13:9:15 | ...! | NullableRefTypes.cs:9:9:9:15 | ... = ... | successor |
+| NullableRefTypes.cs:10:9:10:16 | ... = ... | NullableRefTypes.cs:11:9:11:15 | ...; | successor |
+| NullableRefTypes.cs:10:9:10:17 | ...; | NullableRefTypes.cs:10:13:10:16 | null | successor |
+| NullableRefTypes.cs:10:13:10:16 | null | NullableRefTypes.cs:10:9:10:16 | ... = ... | successor |
+| NullableRefTypes.cs:11:9:11:14 | ... = ... | NullableRefTypes.cs:5:10:5:29 | exit TestNullableRefTypes | successor |
+| NullableRefTypes.cs:11:9:11:15 | ...; | NullableRefTypes.cs:11:13:11:13 | access to local variable x | successor |
+| NullableRefTypes.cs:11:13:11:13 | access to local variable x | NullableRefTypes.cs:11:13:11:14 | ...! | successor |
+| NullableRefTypes.cs:11:13:11:14 | ...! | NullableRefTypes.cs:11:9:11:14 | ... = ... | successor |
+nonNullExpressions
+| NullableRefTypes.cs:7:21:7:28 | "source" |
+| NullableRefTypes.cs:8:20:8:20 | access to local variable x |
+| NullableRefTypes.cs:8:20:8:21 | ...! |
+| NullableRefTypes.cs:9:9:9:15 | ... = ... |
+| NullableRefTypes.cs:9:13:9:13 | access to local variable x |
+| NullableRefTypes.cs:9:13:9:14 | ...! |
+| NullableRefTypes.cs:9:13:9:15 | ...! |
+| NullableRefTypes.cs:11:9:11:14 | ... = ... |
+| NullableRefTypes.cs:11:13:11:14 | ...! |

csharp/ql/test/library-tests/csharp8/NullableRefTypes.ql

@@ -1,4 +1,5 @@
 import csharp
+import semmle.code.csharp.dataflow.Nullness
 
 query predicate suppressNullableWarnings(SuppressNullableWarningExpr e, Expr op) {
   op = e.getExpr()
@@ -15,3 +16,7 @@ query predicate nullableControlFlow(
   a.getEnclosingCallable().hasName("TestNullableRefTypes") and
   b = a.getASuccessorByType(t)
 }
+
+query predicate nonNullExpressions(NonNullExpr e) {
+  e.getEnclosingCallable().getName() = "TestNullableRefTypes"
+}