C#: Replace Ssa::ImplicitParameterDefinition with SsaParameterInit.

Author: aschackmull

csharp/ql/lib/semmle/code/csharp/dataflow/Nullness.qll

@@ -126,7 +126,7 @@ private predicate nonNullDef(SsaExplicitWrite def) {
  */
 private predicate dereferenceAt(SsaDefinition def, Dereference d) { d = def.getARead() }
 
-private predicate isMaybeNullArgument(Ssa::ParameterDefinition def, MaybeNullExpr arg) {
+private predicate isMaybeNullArgument(SsaParameterInit def, MaybeNullExpr arg) {
   exists(AssignableDefinitions::ImplicitParameterDefinition pdef, Parameter p |
     p = def.getParameter()
   |
@@ -320,9 +320,7 @@ class Dereference extends G::DereferenceableExpr {
         not p.getAnnotatedType().isNullableRefType()
         or
         p.fromSource() and
-        exists(
-          Ssa::ParameterDefinition def, AssignableDefinitions::ImplicitParameterDefinition pdef
-        |
+        exists(SsaParameterInit def, AssignableDefinitions::ImplicitParameterDefinition pdef |
           p = def.getParameter()
         |
           p.getUnboundDeclaration() = pdef.getParameter() and

csharp/ql/lib/semmle/code/csharp/dataflow/SSA.qll

@@ -553,6 +553,9 @@ module Ssa {
     }
   }
 
+  /**
+   * DEPRECATED: Use `SsaParameterInit` instead.
+   */
   deprecated class ImplicitParameterDefinition = ParameterDefinition;
 
   final class ParameterDefinition = SsaImpl::ParameterDefinitionImpl;

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

@@ -1302,12 +1302,6 @@ private module NearestLocationInputParamAfterCallable implements NearestLocation
 }
 
 private module ParameterNodes {
-  pragma[nomagic]
-  private predicate ssaParamDef(Ssa::ParameterDefinition ssaDef, Parameter p, Location l) {
-    p = ssaDef.getParameter() and
-    l = ssaDef.getLocation()
-  }
-
   private module NearestLocationInputParamBeforeCallable implements NearestLocationInputSig {
     class C = Parameter;
 
@@ -1358,11 +1352,9 @@ private module ParameterNodes {
     }
 
     /** Gets the SSA definition corresponding to this parameter, if any. */
-    Ssa::ParameterDefinition getSsaDefinition() {
-      exists(Parameter p, Location l |
-        l = this.getParameterLocation(p) and
-        ssaParamDef(result, p, l)
-      )
+    SsaParameterInit getSsaDefinition() {
+      result.getParameter() = parameter and
+      result.getBasicBlock() = callable.getABasicBlock()
     }
 
     override predicate isParameterOf(DataFlowCallable c, ParameterPosition pos) {

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

@@ -1017,7 +1017,7 @@ private module DataFlowIntegrationInput implements Impl::DataFlowIntegrationInpu
   predicate ssaDefHasSource(WriteDefinition def) {
     // exclude flow directly from RHS to SSA definition, as we instead want to
     // go from RHS to matching assignable definition, and from there to SSA definition
-    def instanceof Ssa::ParameterDefinition
+    def instanceof SsaParameterInit
   }
 
   /**

csharp/ql/test/library-tests/dataflow/defuse/parameterUseEquivalence.ql

@@ -24,7 +24,7 @@ private LocalScopeVariableRead getAReachableUncertainRead(
   AssignableDefinitions::ImplicitParameterDefinition p
 ) {
   exists(SsaDefinition ssaDef |
-    p.getParameter() = ssaDef.getAnUltimateDefinition().(Ssa::ParameterDefinition).getParameter()
+    p.getParameter() = ssaDef.getAnUltimateDefinition().(SsaParameterInit).getParameter()
   |
     result = ssaDef.getARead()
   )

csharp/ql/test/library-tests/dataflow/ssa/SsaImplicitParameterDef.ql

@@ -1,5 +1,5 @@
 import csharp
 
-from Ssa::SourceVariable v, Ssa::ParameterDefinition def
+from Ssa::SourceVariable v, SsaParameterInit def
 where v = def.getSourceVariable()
 select v, def, def.getParameter()