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michaelnebelmichaelnebel
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Merge pull request #15652 from michaelnebel/csharp/constructorflow
C#: Read-only property flow.
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‎csharp/ql/lib/change-notes/2024-02-21-getonly-properties.md

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---
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category: minorAnalysis
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---
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* C#: Data flow via get only properties like `public object Obj { get; }` is now captured by the data flow library.

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

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@@ -127,6 +127,13 @@ class Property extends DotNet::Property, DeclarationWithGetSetAccessors, @proper
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properties(this, _, _, getTypeRef(result), _)
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}
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private predicate isAutoPartial() {
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this.fromSource() and
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not this.isExtern() and
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not this.isAbstract() and
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not this.getAnAccessor().hasBody()
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}
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/**
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* Holds if this property is automatically implemented. For example, `P1`
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* on line 2 is automatically implemented, while `P2` on line 5 is not in
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* code.
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*/
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predicate isAutoImplemented() {
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this.fromSource() and
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this.isReadWrite() and
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not this.isExtern() and
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not this.isAbstract() and
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not this.getAnAccessor().hasBody()
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this.isAutoPartial() and
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this.isReadWrite()
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}
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/**
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* Holds if this property is automatically implemented and read-only. For
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* example, `P1` on line 2 is automatically implemented and read-only
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* ```csharp
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* class C {
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* public int P1 { get; }
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* }
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* ```
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*/
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predicate isAutoImplementedReadOnly() {
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this.isAutoPartial() and
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this.isReadOnly()
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}
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override Property getUnboundDeclaration() { properties(this, _, _, _, result) }

‎csharp/ql/lib/semmle/code/csharp/dataflow/internal/DataFlowPrivate.qll

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@@ -1899,6 +1899,8 @@ class FieldOrProperty extends Assignable, Modifiable {
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(
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p.isAutoImplemented()
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or
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p.isAutoImplementedReadOnly()
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or
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p.matchesHandle(any(CIL::TrivialProperty tp))
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or
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p.getDeclaringType() instanceof AnonymousClass

‎csharp/ql/test/library-tests/dataflow/constructors/ConstructorFlow.expected

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| Constructors.cs:112:25:112:27 | access to local variable o31 : Object | Constructors.cs:112:18:112:28 | object creation of type C3 : C3 [parameter o31param] : Object | provenance | |
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| Constructors.cs:113:14:113:15 | access to local variable c3 : C3 [parameter o31param] : Object | Constructors.cs:106:32:106:39 | this : C3 [parameter o31param] : Object | provenance | |
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| Constructors.cs:113:14:113:15 | access to local variable c3 : C3 [parameter o31param] : Object | Constructors.cs:113:14:113:21 | access to property Obj31 | provenance | |
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| Constructors.cs:121:26:121:28 | oc1 : Object | Constructors.cs:123:20:123:22 | access to parameter oc1 : Object | provenance | |
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| Constructors.cs:121:38:121:40 | oc2 : Object | Constructors.cs:124:20:124:22 | access to parameter oc2 : Object | provenance | |
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| Constructors.cs:123:20:123:22 | access to parameter oc1 : Object | Constructors.cs:123:13:123:16 | [post] this access : C4 [property Obj1] : Object | provenance | |
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| Constructors.cs:124:20:124:22 | access to parameter oc2 : Object | Constructors.cs:124:13:124:16 | [post] this access : C4 [property Obj2] : Object | provenance | |
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| Constructors.cs:130:18:130:34 | call to method Source<Object> : Object | Constructors.cs:132:25:132:26 | access to local variable o1 : Object | provenance | |
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| Constructors.cs:131:18:131:34 | call to method Source<Object> : Object | Constructors.cs:132:29:132:30 | access to local variable o2 : Object | provenance | |
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| Constructors.cs:132:18:132:31 | object creation of type C4 : C4 [property Obj1] : Object | Constructors.cs:133:14:133:15 | access to local variable c4 : C4 [property Obj1] : Object | provenance | |
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| Constructors.cs:132:18:132:31 | object creation of type C4 : C4 [property Obj2] : Object | Constructors.cs:134:14:134:15 | access to local variable c4 : C4 [property Obj2] : Object | provenance | |
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| Constructors.cs:132:25:132:26 | access to local variable o1 : Object | Constructors.cs:121:26:121:28 | oc1 : Object | provenance | |
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| Constructors.cs:132:25:132:26 | access to local variable o1 : Object | Constructors.cs:132:18:132:31 | object creation of type C4 : C4 [property Obj1] : Object | provenance | |
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| Constructors.cs:132:29:132:30 | access to local variable o2 : Object | Constructors.cs:121:38:121:40 | oc2 : Object | provenance | |
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| Constructors.cs:132:29:132:30 | access to local variable o2 : Object | Constructors.cs:132:18:132:31 | object creation of type C4 : C4 [property Obj2] : Object | provenance | |
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| Constructors.cs:133:14:133:15 | access to local variable c4 : C4 [property Obj1] : Object | Constructors.cs:133:14:133:20 | access to property Obj1 | provenance | |
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| Constructors.cs:134:14:134:15 | access to local variable c4 : C4 [property Obj2] : Object | Constructors.cs:134:14:134:20 | access to property Obj2 | provenance | |
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nodes
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| Constructors.cs:5:24:5:25 | [post] this access : C_no_ctor [field s1] : Object | semmle.label | [post] this access : C_no_ctor [field s1] : Object |
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| Constructors.cs:5:29:5:45 | call to method Source<Object> : Object | semmle.label | call to method Source<Object> : Object |
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| Constructors.cs:112:25:112:27 | access to local variable o31 : Object | semmle.label | access to local variable o31 : Object |
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| Constructors.cs:113:14:113:15 | access to local variable c3 : C3 [parameter o31param] : Object | semmle.label | access to local variable c3 : C3 [parameter o31param] : Object |
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| Constructors.cs:113:14:113:21 | access to property Obj31 | semmle.label | access to property Obj31 |
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| Constructors.cs:121:26:121:28 | oc1 : Object | semmle.label | oc1 : Object |
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| Constructors.cs:121:38:121:40 | oc2 : Object | semmle.label | oc2 : Object |
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| Constructors.cs:123:13:123:16 | [post] this access : C4 [property Obj1] : Object | semmle.label | [post] this access : C4 [property Obj1] : Object |
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| Constructors.cs:123:20:123:22 | access to parameter oc1 : Object | semmle.label | access to parameter oc1 : Object |
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| Constructors.cs:124:13:124:16 | [post] this access : C4 [property Obj2] : Object | semmle.label | [post] this access : C4 [property Obj2] : Object |
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| Constructors.cs:124:20:124:22 | access to parameter oc2 : Object | semmle.label | access to parameter oc2 : Object |
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| Constructors.cs:130:18:130:34 | call to method Source<Object> : Object | semmle.label | call to method Source<Object> : Object |
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| Constructors.cs:131:18:131:34 | call to method Source<Object> : Object | semmle.label | call to method Source<Object> : Object |
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| Constructors.cs:132:18:132:31 | object creation of type C4 : C4 [property Obj1] : Object | semmle.label | object creation of type C4 : C4 [property Obj1] : Object |
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| Constructors.cs:132:18:132:31 | object creation of type C4 : C4 [property Obj2] : Object | semmle.label | object creation of type C4 : C4 [property Obj2] : Object |
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| Constructors.cs:132:25:132:26 | access to local variable o1 : Object | semmle.label | access to local variable o1 : Object |
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| Constructors.cs:132:29:132:30 | access to local variable o2 : Object | semmle.label | access to local variable o2 : Object |
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| Constructors.cs:133:14:133:15 | access to local variable c4 : C4 [property Obj1] : Object | semmle.label | access to local variable c4 : C4 [property Obj1] : Object |
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| Constructors.cs:133:14:133:20 | access to property Obj1 | semmle.label | access to property Obj1 |
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| Constructors.cs:134:14:134:15 | access to local variable c4 : C4 [property Obj2] : Object | semmle.label | access to local variable c4 : C4 [property Obj2] : Object |
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| Constructors.cs:134:14:134:20 | access to property Obj2 | semmle.label | access to property Obj2 |
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subpaths
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| Constructors.cs:64:37:64:37 | access to parameter o : Object | Constructors.cs:57:54:57:55 | o2 : Object | Constructors.cs:59:13:59:19 | SSA def(o1) : Object | Constructors.cs:64:27:64:34 | SSA def(o22param) : Object |
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| Constructors.cs:71:25:71:25 | access to local variable o : Object | Constructors.cs:41:26:41:26 | o : Object | Constructors.cs:41:32:41:34 | [post] this access : C1 [field Obj] : Object | Constructors.cs:71:18:71:26 | object creation of type C1 : C1 [field Obj] : Object |
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| Constructors.cs:101:14:101:15 | access to local variable c2 : C2 [parameter o22param] : Object | Constructors.cs:48:32:48:39 | this : C2 [parameter o22param] : Object | Constructors.cs:48:32:48:39 | access to parameter o22param : Object | Constructors.cs:101:14:101:21 | access to property Obj22 |
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| Constructors.cs:112:25:112:27 | access to local variable o31 : Object | Constructors.cs:104:28:104:35 | o31param : Object | Constructors.cs:104:28:104:35 | o31param : Object | Constructors.cs:112:18:112:28 | object creation of type C3 : C3 [parameter o31param] : Object |
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| Constructors.cs:113:14:113:15 | access to local variable c3 : C3 [parameter o31param] : Object | Constructors.cs:106:32:106:39 | this : C3 [parameter o31param] : Object | Constructors.cs:106:32:106:39 | access to parameter o31param : Object | Constructors.cs:113:14:113:21 | access to property Obj31 |
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| Constructors.cs:132:25:132:26 | access to local variable o1 : Object | Constructors.cs:121:26:121:28 | oc1 : Object | Constructors.cs:123:13:123:16 | [post] this access : C4 [property Obj1] : Object | Constructors.cs:132:18:132:31 | object creation of type C4 : C4 [property Obj1] : Object |
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| Constructors.cs:132:29:132:30 | access to local variable o2 : Object | Constructors.cs:121:38:121:40 | oc2 : Object | Constructors.cs:124:13:124:16 | [post] this access : C4 [property Obj2] : Object | Constructors.cs:132:18:132:31 | object creation of type C4 : C4 [property Obj2] : Object |
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#select
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| Constructors.cs:15:18:15:19 | access to field s1 | Constructors.cs:5:29:5:45 | call to method Source<Object> : Object | Constructors.cs:15:18:15:19 | access to field s1 | $@ | Constructors.cs:5:29:5:45 | call to method Source<Object> : Object | call to method Source<Object> : Object |
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| Constructors.cs:33:18:33:19 | access to field s1 | Constructors.cs:21:29:21:45 | call to method Source<Object> : Object | Constructors.cs:33:18:33:19 | access to field s1 | $@ | Constructors.cs:21:29:21:45 | call to method Source<Object> : Object | call to method Source<Object> : Object |
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| Constructors.cs:93:14:93:21 | access to property Obj22 | Constructors.cs:91:21:91:37 | call to method Source<Object> : Object | Constructors.cs:93:14:93:21 | access to property Obj22 | $@ | Constructors.cs:91:21:91:37 | call to method Source<Object> : Object | call to method Source<Object> : Object |
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| Constructors.cs:101:14:101:21 | access to property Obj22 | Constructors.cs:99:21:99:37 | call to method Source<Object> : Object | Constructors.cs:101:14:101:21 | access to property Obj22 | $@ | Constructors.cs:99:21:99:37 | call to method Source<Object> : Object | call to method Source<Object> : Object |
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| Constructors.cs:113:14:113:21 | access to property Obj31 | Constructors.cs:111:19:111:35 | call to method Source<Object> : Object | Constructors.cs:113:14:113:21 | access to property Obj31 | $@ | Constructors.cs:111:19:111:35 | call to method Source<Object> : Object | call to method Source<Object> : Object |
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| Constructors.cs:133:14:133:20 | access to property Obj1 | Constructors.cs:130:18:130:34 | call to method Source<Object> : Object | Constructors.cs:133:14:133:20 | access to property Obj1 | $@ | Constructors.cs:130:18:130:34 | call to method Source<Object> : Object | call to method Source<Object> : Object |
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| Constructors.cs:134:14:134:20 | access to property Obj2 | Constructors.cs:131:18:131:34 | call to method Source<Object> : Object | Constructors.cs:134:14:134:20 | access to property Obj2 | $@ | Constructors.cs:131:18:131:34 | call to method Source<Object> : Object | call to method Source<Object> : Object |

‎csharp/ql/test/library-tests/dataflow/constructors/Constructors.cs

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Sink(c3.Obj31); // $ hasValueFlow=6
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}
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public class C4
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{
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public object Obj1 { get; init; }
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public object Obj2 { get; }
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public C4(object oc1, object oc2)
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{
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Obj1 = oc1;
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Obj2 = oc2;
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}
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}
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public void M6()
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{
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var o1 = Source<object>(7);
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var o2 = Source<object>(8);
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var c4 = new C4(o1, o2);
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Sink(c4.Obj1); // $ hasValueFlow=7
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Sink(c4.Obj2); // $ hasValueFlow=8
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}
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public static void Sink(object o) { }
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public static T Source<T>(object source) => throw null;

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