Rework foreach_stmt_info extraction

csharp/extractor/Semmle.Extraction.CSharp/Entities/Statements/ForEach.cs

@@ -8,6 +8,15 @@ namespace Semmle.Extraction.CSharp.Entities.Statements
 {
     internal class ForEach : Statement<ForEachStatementSyntax>
     {
+        internal enum ForeachSymbolType
+        {
+            GetEnumeratorMethod = 1,
+            CurrentProperty,
+            MoveNextMethod,
+            DisposeMethod,
+            ElementType
+        }
+
         private ForEach(Context cx, ForEachStatementSyntax stmt, IStatementParentEntity parent, int child)
             : base(cx, stmt, StmtKind.FOREACH, parent, child) { }
 
@@ -33,13 +42,44 @@ namespace Semmle.Extraction.CSharp.Entities.Statements
             Statement.Create(cx, Stmt.Statement, this, 2);
 
             var info = semanticModel.GetForEachStatementInfo(Stmt);
-            var getEnumerator = Method.Create(cx, info.GetEnumeratorMethod);
-            var currentProp = Property.Create(cx, info.CurrentProperty);
-            var moveNext = Method.Create(cx, info.MoveNextMethod);
-            var dispose = Method.Create(cx, info.DisposeMethod);
-            var elementType = Type.Create(cx, info.ElementType);
 
-            trapFile.foreach_stmt_info(this, elementType, getEnumerator, moveNext, dispose, currentProp, info.IsAsynchronous);
+            if (info.Equals(default))
+            {
+                cx.ExtractionError("Could not get foreach statement info", null, Location.Create(cx, this.ReportingLocation), severity: Util.Logging.Severity.Info);
+                return;
+            }
+
+            trapFile.foreach_stmt_info(this, info.IsAsynchronous);
+
+            if (info.GetEnumeratorMethod != null)
+            {
+                var m = Method.Create(cx, info.GetEnumeratorMethod);
+                trapFile.foreach_stmt_desugar(this, m, ForeachSymbolType.GetEnumeratorMethod);
+            }
+
+            if (info.MoveNextMethod != null)
+            {
+                var m = Method.Create(cx, info.MoveNextMethod);
+                trapFile.foreach_stmt_desugar(this, m, ForeachSymbolType.MoveNextMethod);
+            }
+
+            if (info.DisposeMethod != null)
+            {
+                var m = Method.Create(cx, info.DisposeMethod);
+                trapFile.foreach_stmt_desugar(this, m, ForeachSymbolType.DisposeMethod);
+            }
+
+            if (info.CurrentProperty != null)
+            {
+                var p = Property.Create(cx, info.CurrentProperty);
+                trapFile.foreach_stmt_desugar(this, p, ForeachSymbolType.CurrentProperty);
+            }
+
+            if (info.ElementType != null)
+            {
+                var t = Type.Create(cx, info.ElementType);
+                trapFile.foreach_stmt_desugar(this, t, ForeachSymbolType.ElementType);
+            }
         }
     }
 

csharp/extractor/Semmle.Extraction.CSharp/Tuples.cs

@@ -53,10 +53,15 @@ namespace Semmle.Extraction.CSharp
             trapFile.WriteTuple("catch_type", @catch, type, explicityCaught ? 1 : 2);
         }
 
-        internal static void foreach_stmt_info(this TextWriter trapFile, Entities.Statements.ForEach @foreach, Type element, Method getEnumerator,
-            Method moveNext, Method dispose, Property current, bool isAsync)
+        internal static void foreach_stmt_info(this TextWriter trapFile, Entities.Statements.ForEach @foreach, bool isAsync)
         {
-            trapFile.WriteTuple("foreach_stmt_info", @foreach, element, getEnumerator, moveNext, dispose, current, isAsync ? 2 : 1);
+            trapFile.WriteTuple("foreach_stmt_info", @foreach, isAsync ? 2 : 1);
+        }
+
+        internal static void foreach_stmt_desugar(this TextWriter trapFile, Entities.Statements.ForEach @foreach, IEntity entity,
+            Entities.Statements.ForEach.ForeachSymbolType type)
+        {
+            trapFile.WriteTuple("foreach_stmt_desugar", @foreach, entity, (int)type);
         }
 
         internal static void commentblock(this TextWriter trapFile, CommentBlock k)

csharp/ql/src/Dead Code/DeadCode.qll

@@ -44,7 +44,7 @@ predicate potentiallyAccessedByForEach(Method m) {
   m.hasName("GetEnumerator") and
   m.getDeclaringType().getABaseType+().hasQualifiedName("System.Collections.IEnumerable")
   or
-  foreach_stmt_info(_, _, m, _, _, _, _)
+  foreach_stmt_desugar(_, m, 1)
 }
 
 predicate isRecursivelyLiveExpression(Expr e) {

csharp/ql/src/semmle/code/csharp/Stmt.qll

@@ -583,25 +583,25 @@ class ForeachStmt extends LoopStmt, @foreach_stmt {
   Expr getIterableExpr() { result = this.getChild(1) }
 
   /** Gets the called `GetEnumerator` method. */
-  Method getGetEnumerator() { foreach_stmt_info(this, _, result, _, _, _, _) }
+  Method getGetEnumerator() { foreach_stmt_desugar(this, result, 1) }
 
   /** Gets the called `MoveNext` or `MoveNextAsync` method. */
-  Method getMoveNext() { foreach_stmt_info(this, _, _, result, _, _, _) }
+  Method getMoveNext() { foreach_stmt_desugar(this, result, 3) }
 
   /** Gets the called `Dispose` or `DisposeAsync` method. */
-  Method getDispose() { foreach_stmt_info(this, _, _, _, result, _, _) }
+  Method getDispose() { foreach_stmt_desugar(this, result, 4) }
 
   /** Gets the called `Current` property. */
-  Property getCurrent() { foreach_stmt_info(this, _, _, _, _, result, _) }
+  Property getCurrent() { foreach_stmt_desugar(this, result, 2) }
 
   /**
    * Gets the intermediate type to which the `Current` property is converted before
    * being converted to the iteration variable type.
    */
-  Type getElementType() { foreach_stmt_info(this, result, _, _, _, _, _) }
+  Type getElementType() { foreach_stmt_desugar(this, result, 5) }
 
   /** Holds if this `foreach` statement is asynchronous. */
-  predicate isAsync() { foreach_stmt_info(this, _, _, _, _, _, 2) }
+  predicate isAsync() { foreach_stmt_info(this, 2) }
 
   override string toString() { result = "foreach (... ... in ...) ..." }
 

csharp/ql/src/semmlecode.csharp.dbscheme

@@ -984,13 +984,16 @@ catch_type(
 
 foreach_stmt_info(
   unique int id: @foreach_stmt ref,
-  int element_type_id: @type_or_ref ref,
-  int getenumerator_id: @method ref,
-  int movenext_id: @method ref,
-  int dispose_id: @method ref,
-  int current_id: @property ref,
   int kind: int ref /* non-async = 1, async = 2 */);
 
+@foreach_symbol =  @method | @property | @type_or_ref;
+
+#keyset[id, kind]
+foreach_stmt_desugar(
+  int id: @foreach_stmt ref,
+  int symbol: @foreach_symbol ref,
+  int kind: int ref /* GetEnumeratorMethod = 1, CurrentProperty = 2, MoveNextMethod = 3, DisposeMethod = 4, ElementType = 5 */);
+
 /** EXPRESSIONS **/
 
 expressions(

csharp/upgrades/TO_CHANGE/upgrade.properties

@@ -1,2 +1,2 @@
-description: Add 'foreach_stmt_info' relation.
+description: Add 'foreach_stmt_info' and 'foreach_stmt_desugar' relations.
 compatibility: backwards