C#: Only extract the unbound locations for constructors, destructors and user defined operators and use this in the QL code.

Author: michaelnebel

csharp/extractor/Semmle.Extraction.CSharp/Entities/Constructor.cs

@@ -29,7 +29,10 @@ public override void Populate(TextWriter trapFile)
             ContainingType!.PopulateGenerics();
 
             trapFile.constructors(this, Symbol.ContainingType.Name, ContainingType, (Constructor)OriginalDefinition);
-            WriteLocationToTrap(trapFile.constructor_location, this, Location);
+            if (Context.ExtractLocation(Symbol) && (!IsDefault || IsBestSourceLocation))
+            {
+                WriteLocationToTrap(trapFile.constructor_location, this, Location);
+            }
 
             if (MakeSynthetic)
             {
@@ -168,7 +171,15 @@ Symbol.ContainingType.TypeKind is TypeKind.Class or TypeKind.Struct &&
             Symbol.ContainingType.IsSourceDeclaration() &&
             !Symbol.ContainingType.IsAnonymousType;
 
-        private bool MakeSynthetic => IsPrimary || IsDefault;
+        /// <summary>
+        /// Returns true if we consider the reporting location of this constructor entity the best
+        /// location of the constructor.
+        /// For partial classes with default constructors, Roslyn consider each partial class declaration
+        /// as the possible location for the implicit default constructor.
+        /// </summary>
+        private bool IsBestSourceLocation => ReportingLocation is not null && Context.IsLocationInContext(ReportingLocation);
+
+        private bool MakeSynthetic => IsPrimary || (IsDefault && IsBestSourceLocation);
 
         [return: NotNullIfNotNull(nameof(constructor))]
         public static new Constructor? Create(Context cx, IMethodSymbol? constructor)

csharp/extractor/Semmle.Extraction.CSharp/Entities/Destructor.cs

@@ -15,7 +15,10 @@ public override void Populate(TextWriter trapFile)
             ContainingType!.PopulateGenerics();
 
             trapFile.destructors(this, $"~{Symbol.ContainingType.Name}", ContainingType, OriginalDefinition(Context, this, Symbol));
-            WriteLocationToTrap(trapFile.destructor_location, this, Location);
+            if (Context.ExtractLocation(Symbol))
+            {
+                WriteLocationToTrap(trapFile.destructor_location, this, Location);
+            }
         }
 
         private static new Destructor OriginalDefinition(Context cx, Destructor original, IMethodSymbol symbol)

csharp/extractor/Semmle.Extraction.CSharp/Entities/UserOperator.cs

@@ -26,7 +26,10 @@ public override void Populate(TextWriter trapFile)
                 returnType.TypeRef,
                 (UserOperator)OriginalDefinition);
 
-            WriteLocationsToTrap(trapFile.operator_location, this, Locations);
+            if (Context.ExtractLocation(Symbol))
+            {
+                WriteLocationsToTrap(trapFile.operator_location, this, Locations);
+            }
 
             if (IsSourceDeclaration)
             {

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

@@ -357,7 +357,7 @@ class Constructor extends Callable, Member, Attributable, @constructor {
 
   override Constructor getUnboundDeclaration() { constructors(this, _, _, result) }
 
-  override Location getALocation() { constructor_location(this, result) }
+  override Location getALocation() { constructor_location(this.getUnboundDeclaration(), result) }
 
   override predicate fromSource() { Member.super.fromSource() and not this.isCompilerGenerated() }
 
@@ -450,7 +450,7 @@ class Destructor extends Callable, Member, Attributable, @destructor {
 
   override Destructor getUnboundDeclaration() { destructors(this, _, _, result) }
 
-  override Location getALocation() { destructor_location(this, result) }
+  override Location getALocation() { destructor_location(this.getUnboundDeclaration(), result) }
 
   override string toString() { result = Callable.super.toString() }
 
@@ -484,7 +484,7 @@ class Operator extends Callable, Member, Attributable, Overridable, @operator {
 
   override Operator getUnboundDeclaration() { operators(this, _, _, _, _, result) }
 
-  override Location getALocation() { operator_location(this, result) }
+  override Location getALocation() { operator_location(this.getUnboundDeclaration(), result) }
 
   override string toString() { result = Callable.super.toString() }