Merge pull request #15296 from michaelnebel/csharp/getruntimeargument

C#: Improve getRuntimeArgumentForParameter to consider named arguments.

csharp/ql/lib/semmle/code/csharp/exprs/Call.qll

@@ -60,18 +60,17 @@ class Call extends DotNet::Call, Expr, @call {
    */
   cached
   override Expr getArgumentForParameter(DotNet::Parameter p) {
+    // Appears in the positional part of the call
+    result = this.getImplicitArgument(p)
+    or
+    // Appears in the named part of the call
     this.getTarget().getAParameter() = p and
-    (
-      // Appears in the positional part of the call
-      result = this.getImplicitArgument(p)
-      or
-      // Appears in the named part of the call
-      result = this.getExplicitArgument(p.getName())
-    )
+    result = this.getExplicitArgument(p.getName())
   }
 
   pragma[noinline]
   private Expr getImplicitArgument(DotNet::Parameter p) {
+    this.getTarget().getAParameter() = p and
     not exists(result.getExplicitArgumentName()) and
     (
       p.(Parameter).isParams() and
@@ -183,24 +182,38 @@ class Call extends DotNet::Call, Expr, @call {
    * Gets the argument that corresponds to parameter `p` of a potential
    * run-time target of this call.
    *
-   * Does not consider
-   *   - default arguments,
-   *   - named arguments.
+   * This takes into account both positional and named arguments, but does not
+   * consider default arguments.
    */
+  cached
   Expr getRuntimeArgumentForParameter(Parameter p) {
-    exists(Callable c |
-      c = this.getARuntimeTarget() and
-      p = c.getAParameter() and
-      (
-        p.isParams() and
-        result = this.getRuntimeArgument(any(int i | i >= p.getPosition()))
-        or
-        not p.isParams() and
-        result = this.getRuntimeArgument(p.getPosition())
-      )
+    // Appears in the positional part of the call
+    result = this.getImplicitRuntimeArgument(p)
+    or
+    // Appears in the named part of the call
+    this.getARuntimeTarget().getAParameter() = p and
+    result = this.getExplicitRuntimeArgument(p.getName())
+  }
+
+  pragma[noinline]
+  private Expr getImplicitRuntimeArgument(Parameter p) {
+    this.getARuntimeTarget().getAParameter() = p and
+    not exists(result.getExplicitArgumentName()) and
+    (
+      p.isParams() and
+      result = this.getRuntimeArgument(any(int i | i >= p.getPosition()))
+      or
+      not p.isParams() and
+      result = this.getRuntimeArgument(p.getPosition())
     )
   }
 
+  pragma[nomagic]
+  private Expr getExplicitRuntimeArgument(string name) {
+    result = this.getARuntimeArgument() and
+    result.getExplicitArgumentName() = name
+  }
+
   /**
    * Gets the argument that corresponds to a parameter named `name` of a potential
    * run-time target of this call.

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

@@ -421,3 +421,30 @@ lambdas.cs:
 #   17|           0: [IntLiteral] 7
 #   17|           1: [IntLiteral] 8
 #   17|           2: [IntLiteral] 9
+#   20|   6: [DelegateType] MyDelegate
+#-----|     2: (Parameters)
+#   20|       0: [Parameter] x
+#   20|         -1: [TypeMention] int
+#   20|       1: [Parameter] y
+#   20|         -1: [TypeMention] int
+#   22|   7: [Method] M2
+#   22|     -1: [TypeMention] Void
+#   23|     4: [BlockStmt] {...}
+#   24|       0: [LocalVariableDeclStmt] ... ...;
+#   24|         0: [LocalVariableDeclAndInitExpr] MyDelegate sum = ...
+#   24|           -1: [TypeMention] MyDelegate
+#   24|           0: [LocalVariableAccess] access to local variable sum
+#   24|           1: [LambdaExpr] (...) => ...
+#-----|             2: (Parameters)
+#   24|               0: [Parameter] x
+#   24|                 -1: [TypeMention] int
+#   24|               1: [Parameter] y
+#   24|                 -1: [TypeMention] int
+#   24|             4: [AddExpr] ... + ...
+#   24|               0: [ParameterAccess] access to parameter x
+#   24|               1: [ParameterAccess] access to parameter y
+#   25|       1: [ExprStmt] ...;
+#   25|         0: [DelegateCall] delegate call
+#   25|           -1: [LocalVariableAccess] access to local variable sum
+#   25|           0: [IntLiteral] 4
+#   25|           1: [IntLiteral] 5

csharp/ql/test/library-tests/arguments/argumentName.expected

@@ -11,3 +11,5 @@
 | arguments.cs:70:36:70:36 | 0 | x |
 | arguments.cs:78:18:78:21 | access to parameter args | args |
 | arguments.cs:78:27:78:27 | 0 | o |
+| lambdas.cs:25:16:25:16 | 4 | y |
+| lambdas.cs:25:22:25:22 | 5 | x |

csharp/ql/test/library-tests/arguments/argumentType.expected

@@ -79,3 +79,5 @@
 | lambdas.cs:17:12:17:12 | 7 | 0 |
 | lambdas.cs:17:15:17:15 | 8 | 0 |
 | lambdas.cs:17:18:17:18 | 9 | 0 |
+| lambdas.cs:25:16:25:16 | 4 | 0 |
+| lambdas.cs:25:22:25:22 | 5 | 0 |

csharp/ql/test/library-tests/arguments/lambdaArgument.expected

@@ -7,3 +7,5 @@
 | lambdas.cs:17:9:17:19 | delegate call | lambdas.cs:15:32:15:32 | x | lambdas.cs:17:12:17:12 | 7 |
 | lambdas.cs:17:9:17:19 | delegate call | lambdas.cs:15:32:15:32 | x | lambdas.cs:17:15:17:15 | 8 |
 | lambdas.cs:17:9:17:19 | delegate call | lambdas.cs:15:32:15:32 | x | lambdas.cs:17:18:17:18 | 9 |
+| lambdas.cs:25:9:25:23 | delegate call | lambdas.cs:24:31:24:31 | x | lambdas.cs:25:22:25:22 | 5 |
+| lambdas.cs:25:9:25:23 | delegate call | lambdas.cs:24:38:24:38 | y | lambdas.cs:25:16:25:16 | 4 |

csharp/ql/test/library-tests/arguments/lambdas.cs

@@ -16,4 +16,13 @@ class LambdaArgumentsTest
         l3();
         l3(7, 8, 9);
     }
+
+    delegate int MyDelegate(int x, int y);
+
+    void M2()
+    {
+        MyDelegate sum = (int x, int y) => x + y;
+        sum(y: 4, x: 5);
+    }
 }
+