C# extractor: extract catch(Ex) type as TypeAccess instead of TypeMention

Author: Copilot

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

@@ -25,7 +25,7 @@ protected override void PopulateStatement(TextWriter trapFile)
             {
                 var type = Type.Create(Context, Context.GetType(Stmt.Declaration!.Type));
                 trapFile.catch_type(this, type.TypeRef, true);
-                TypeMention.Create(Context, Stmt.Declaration!.Type, this, type);
+                Expression.Create(Context, Stmt.Declaration!.Type, this, 0);
             }
             else // A catch clause of the form 'catch { ... }'
             {

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

@@ -995,6 +995,23 @@ class SpecificCatchClause extends CatchClause {
   /** Gets the local variable declaration of this catch clause, if any. */
   LocalVariableDeclExpr getVariableDeclExpr() { result.getParent() = this }
 
+  /**
+   * Gets the type access of this catch clause, if it has no variable declaration.
+   *
+   * For example, the type access in
+   *
+   * ```csharp
+   * try { ... }
+   * catch (IOException) { ... }
+   * ```
+   *
+   * is `IOException`.
+   */
+  TypeAccess getTypeAccess() {
+    not exists(this.getVariableDeclExpr()) and
+    result = this.getChild(0)
+  }
+
   override string toString() { result = "catch (...) {...}" }
 
   override string getAPrimaryQlClass() { result = "SpecificCatchClause" }

csharp/ql/lib/semmle/code/csharp/controlflow/internal/ControlFlowGraph.qll

@@ -90,6 +90,7 @@ module Ast implements AstSig<Location> {
   private AstNode getStmtChild0(Stmt s, int i) {
     not s instanceof FixedStmt and
     not s instanceof UsingBlockStmt and
+    not skipControlFlow(result) and
     result = s.getChild(i)
     or
     s =

csharp/ql/src/change-notes/2026-06-23-catch-type-access.md

@@ -0,0 +1,4 @@
+---
+category: minorAnalysis
+---
+* The C# extractor now extracts the exception type in a `catch(ExceptionType)` clause (without a variable) as a `TypeAccess` expression instead of a `TypeMention`. The new `SpecificCatchClause.getTypeAccess()` predicate provides access to this expression.

csharp/ql/test/library-tests/csharp6/PrintAst.expected

@@ -101,7 +101,8 @@ csharp6.cs:
 #   32|                   0: [IntLiteral] 2
 #   32|                 0: [IntLiteral] 1
 #   34|         1: [SpecificCatchClause] catch (...) {...}
-#   34|           0: [TypeMention] IndexOutOfRangeException
+#   34|           0: [TypeAccess] access to type IndexOutOfRangeException
+#   34|             0: [TypeMention] IndexOutOfRangeException
 #   35|           1: [BlockStmt] {...}
 #   34|           2: [EQExpr] ... == ...
 #   34|             0: [PropertyCall] access to property Value

csharp/ql/test/library-tests/statements/Checked1.expected

@@ -1 +1 @@
-| statements.cs:234:13:237:13 | checked {...} | statements.cs:235:13:237:13 | {...} |
+| statements.cs:250:13:253:13 | checked {...} | statements.cs:251:13:253:13 | {...} |

csharp/ql/test/library-tests/statements/CompilerGenerated.expected

@@ -1,3 +1,3 @@
 | fixed.cs:3:7:3:11 | {...} | fixed.cs:3:7:3:11 | Fixed |
 | statements.cs:8:11:8:15 | {...} | statements.cs:8:11:8:15 | Class |
-| statements.cs:244:15:244:25 | {...} | statements.cs:244:15:244:25 | AccountLock |
+| statements.cs:260:15:260:25 | {...} | statements.cs:260:15:260:25 | AccountLock |

csharp/ql/test/library-tests/statements/Labeled1.expected

@@ -1 +1 @@
-| statements.cs:273:21:273:31 | MainLabeled | statements.cs:276:9:276:13 | Label: |
+| statements.cs:289:21:289:31 | MainLabeled | statements.cs:292:9:292:13 | Label: |

csharp/ql/test/library-tests/statements/Lock2.expected

@@ -1 +1 @@
-| statements.cs:249:17:256:17 | lock (...) {...} | statements.cs:249:23:249:26 | this access | statements.cs:250:17:256:17 | {...} |
+| statements.cs:265:17:272:17 | lock (...) {...} | statements.cs:265:23:265:26 | this access | statements.cs:266:17:272:17 | {...} |

csharp/ql/test/library-tests/statements/Lock3.expected

@@ -1 +1 @@
-| statements.cs:285:13:288:13 | lock (...) {...} | statements.cs:285:19:285:28 | access to field lockObject | Lock | statements.cs:286:13:288:13 | {...} |
+| statements.cs:301:13:304:13 | lock (...) {...} | statements.cs:301:19:301:28 | access to field lockObject | Lock | statements.cs:302:13:304:13 | {...} |