From de96b5acfd8910ec6e4970f5c3bad0362d01f3c4 Mon Sep 17 00:00:00 2001
From: Anders Schack-Mulligen <aschackmull@github.com>
Date: Tue, 28 Apr 2026 11:15:13 +0200
Subject: [PATCH] C#: Deprecate Ssa::ImplicitDefinition.

---
 csharp/ql/lib/semmle/code/csharp/dataflow/SSA.qll         | 8 +++++---
 .../code/csharp/dataflow/internal/DataFlowPrivate.qll     | 4 ++--
 .../internal/rangeanalysis/SignAnalysisSpecific.qll       | 4 ++--
 3 files changed, 9 insertions(+), 7 deletions(-)

diff --git a/csharp/ql/lib/semmle/code/csharp/dataflow/SSA.qll b/csharp/ql/lib/semmle/code/csharp/dataflow/SSA.qll
index edc7e6a6a89..be265188e5d 100644
--- a/csharp/ql/lib/semmle/code/csharp/dataflow/SSA.qll
+++ b/csharp/ql/lib/semmle/code/csharp/dataflow/SSA.qll
@@ -509,13 +509,15 @@ module Ssa {
   }
 
   /**
+   * DEPRECATED: Use `SsaParameterInit` or `SsaImplicitWrite` instead.
+   *
    * An SSA definition that does not correspond to an explicit variable definition.
    * Either an implicit initialization of a variable at the beginning of a callable
    * (`ImplicitEntryDefinition`), an implicit definition via a call
    * (`ImplicitCallDefinition`), or an implicit definition where the qualifier is
    * updated (`ImplicitQualifierDefinition`).
    */
-  class ImplicitDefinition extends Definition, SsaImpl::WriteDefinition {
+  deprecated class ImplicitDefinition extends Definition, SsaImpl::WriteDefinition {
     ImplicitDefinition() {
       exists(BasicBlock bb, SourceVariable v, int i | this.definesAt(v, bb, i) |
         SsaImpl::implicitEntryDefinition(bb, v) and
@@ -596,7 +598,7 @@ module Ssa {
    * An SSA definition representing the potential definition of a variable
    * via a call.
    */
-  class ImplicitCallDefinition extends ImplicitDefinition {
+  class ImplicitCallDefinition extends SsaImplicitWrite {
     private Call c;
 
     ImplicitCallDefinition() {
@@ -629,7 +631,7 @@ module Ssa {
    * An SSA definition representing the potential definition of a variable
    * via an SSA definition for the qualifier.
    */
-  class ImplicitQualifierDefinition extends ImplicitDefinition, SsaImpl::WriteDefinition {
+  class ImplicitQualifierDefinition extends SsaImplicitWrite {
     private Definition q;
 
     ImplicitQualifierDefinition() {
diff --git a/csharp/ql/lib/semmle/code/csharp/dataflow/internal/DataFlowPrivate.qll b/csharp/ql/lib/semmle/code/csharp/dataflow/internal/DataFlowPrivate.qll
index 7b1d35c6e5a..ccf65ddb37c 100644
--- a/csharp/ql/lib/semmle/code/csharp/dataflow/internal/DataFlowPrivate.qll
+++ b/csharp/ql/lib/semmle/code/csharp/dataflow/internal/DataFlowPrivate.qll
@@ -2008,9 +2008,9 @@ private class FieldOrPropertyRead extends FieldOrPropertyAccess, AssignableRead
    * SSA updates.
    */
   predicate hasNonlocalValue() {
-    exists(SsaDefinition def, Ssa::ImplicitDefinition idef |
+    exists(SsaDefinition def |
       def.getARead() = this and
-      idef = def.getAnUltimateDefinition()
+      def.getAnUltimateDefinition() instanceof SsaImplicitWrite
     )
   }
 }
diff --git a/csharp/ql/lib/semmle/code/csharp/dataflow/internal/rangeanalysis/SignAnalysisSpecific.qll b/csharp/ql/lib/semmle/code/csharp/dataflow/internal/rangeanalysis/SignAnalysisSpecific.qll
index 77e30d239fd..48ed00858a0 100644
--- a/csharp/ql/lib/semmle/code/csharp/dataflow/internal/rangeanalysis/SignAnalysisSpecific.qll
+++ b/csharp/ql/lib/semmle/code/csharp/dataflow/internal/rangeanalysis/SignAnalysisSpecific.qll
@@ -144,12 +144,12 @@ private module Impl {
   }
 
   /** Gets the variable underlying the implicit SSA variable `def`. */
-  Declaration getImplicitSsaDeclaration(Ssa::ImplicitDefinition def) {
+  Declaration getImplicitSsaDeclaration(SsaImplicitWrite def) {
     result = def.getSourceVariable().getAssignable()
   }
 
   /** Holds if the variable underlying the implicit SSA variable `def` is not a field. */
-  predicate nonFieldImplicitSsaDefinition(Ssa::ImplicitDefinition def) {
+  predicate nonFieldImplicitSsaDefinition(SsaImplicitWrite def) {
     not getImplicitSsaDeclaration(def) instanceof Field
   }