implicitToString.cs:
#    3| [Class] TestClass
#    5|   5: [Class] MyClass
#    5|     4: [InstanceConstructor,PrimaryConstructor] MyClass
#    7|     5: [Method] ToString
#    7|       -1: [TypeMention] string
#    8|       4: [BlockStmt] {...}
#    9|         0: [ReturnStmt] return ...;
#    9|           0: [StringLiteralUtf16] "tainted"
#   13|   6: [Method] Sink
#   13|     -1: [TypeMention] Void
#-----|     2: (Parameters)
#   13|       0: [Parameter] o
#   13|         -1: [TypeMention] object
#   13|     4: [BlockStmt] {...}
#   15|   7: [Method] M1
#   15|     -1: [TypeMention] Void
#   16|     4: [BlockStmt] {...}
#   17|       0: [LocalVariableDeclStmt] ... ...;
#   17|         0: [LocalVariableDeclAndInitExpr] MyClass x1 = ...
#   17|           -1: [TypeMention] MyClass
#   17|           0: [LocalVariableAccess] access to local variable x1
#   17|           1: [ObjectCreation] object creation of type MyClass
#   17|             0: [TypeMention] MyClass
#   18|       1: [LocalVariableDeclStmt] ... ...;
#   18|         0: [LocalVariableDeclAndInitExpr] String x2 = ...
#   18|           -1: [TypeMention] string
#   18|           0: [LocalVariableAccess] access to local variable x2
#   18|           1: [AddExpr] ... + ...
#   18|             0: [StringLiteralUtf16] "Hello"
#   18|             1: [MethodCall] call to method ToString
#   18|               -1: [LocalVariableAccess] access to local variable x1
#   19|       2: [ExprStmt] ...;
#   19|         0: [MethodCall] call to method Sink
#   19|           0: [LocalVariableAccess] access to local variable x2
#   22|   8: [Method] M2
#   22|     -1: [TypeMention] Void
#   23|     4: [BlockStmt] {...}
#   24|       0: [LocalVariableDeclStmt] ... ...;
#   24|         0: [LocalVariableDeclAndInitExpr] MyClass x1 = ...
#   24|           -1: [TypeMention] MyClass
#   24|           0: [LocalVariableAccess] access to local variable x1
#   24|           1: [ObjectCreation] object creation of type MyClass
#   24|             0: [TypeMention] MyClass
#   25|       1: [LocalVariableDeclStmt] ... ...;
#   25|         0: [LocalVariableDeclAndInitExpr] String x2 = ...
#   25|           -1: [TypeMention] string
#   25|           0: [LocalVariableAccess] access to local variable x2
#   25|           1: [AddExpr] ... + ...
#   25|             0: [StringLiteralUtf16] "Hello"
#   25|             1: [MethodCall] call to method ToString
#   25|               -1: [LocalVariableAccess] access to local variable x1
#   26|       2: [ExprStmt] ...;
#   26|         0: [MethodCall] call to method Sink
#   26|           0: [LocalVariableAccess] access to local variable x2
#   29|   9: [Method] M3
#   29|     -1: [TypeMention] Void
#   30|     4: [BlockStmt] {...}
#   31|       0: [LocalVariableDeclStmt] ... ...;
#   31|         0: [LocalVariableDeclAndInitExpr] MyClass x1 = ...
#   31|           -1: [TypeMention] MyClass
#   31|           0: [LocalVariableAccess] access to local variable x1
#   31|           1: [ObjectCreation] object creation of type MyClass
#   31|             0: [TypeMention] MyClass
#   32|       1: [LocalVariableDeclStmt] ... ...;
#   32|         0: [LocalVariableDeclAndInitExpr] String x2 = ...
#   32|           -1: [TypeMention] string
#   32|           0: [LocalVariableAccess] access to local variable x2
#   32|           1: [InterpolatedStringExpr] $"..."
#   32|             0: [StringLiteralUtf16] "Hello "
#   32|             1: [InterpolatedStringInsertExpr] {...}
#   32|               0: [MethodCall] call to method ToString
#   32|                 -1: [LocalVariableAccess] access to local variable x1
#   33|       2: [ExprStmt] ...;
#   33|         0: [MethodCall] call to method Sink
#   33|           0: [LocalVariableAccess] access to local variable x2
#   36|   10: [Method] M4
#   36|     -1: [TypeMention] Void
#   37|     4: [BlockStmt] {...}
#   38|       0: [LocalVariableDeclStmt] ... ...;
#   38|         0: [LocalVariableDeclAndInitExpr] MyClass x1 = ...
#   38|           -1: [TypeMention] MyClass
#   38|           0: [LocalVariableAccess] access to local variable x1
#   38|           1: [ObjectCreation] object creation of type MyClass
#   38|             0: [TypeMention] MyClass
#   39|       1: [LocalVariableDeclStmt] ... ...;
#   39|         0: [LocalVariableDeclAndInitExpr] String x2 = ...
#   39|           -1: [TypeMention] string
#   39|           0: [LocalVariableAccess] access to local variable x2
#   39|           1: [InterpolatedStringExpr] $"..."
#   39|             0: [StringLiteralUtf16] "Hello "
#   39|             1: [InterpolatedStringInsertExpr] {...}
#   39|               0: [MethodCall] call to method ToString
#   39|                 -1: [LocalVariableAccess] access to local variable x1
#   40|       2: [ExprStmt] ...;
#   40|         0: [MethodCall] call to method Sink
#   40|           0: [LocalVariableAccess] access to local variable x2