Java: Replace SSA wrapper classes with shared implementation.

java/ql/lib/semmle/code/java/Expr.qll

@@ -1808,6 +1808,52 @@ class VariableAssign extends VariableUpdate {
   }
 }
 
+private newtype TVariableWrite =
+  TParamInit(Parameter p) or
+  TVarWriteExpr(VariableUpdate u)
+
+/**
+ * A write to a variable. This is either a local variable declaration,
+ * including parameter declarations, or an update to a variable.
+ */
+class VariableWrite extends TVariableWrite {
+  /** Gets the expression representing this write, if any. */
+  Expr asExpr() { this = TVarWriteExpr(result) }
+
+  /**
+   * Gets the expression with the value being written, if any.
+   *
+   * This can be the same expression as returned by `asExpr()`, which is the
+   * case for, for example, `++x` and `x += e`. For simple assignments like
+   * `x = e`, `asExpr()` gets the whole assignment expression while
+   * `getValue()` gets the right-hand side `e`. Post-crement operations like
+   * `x++` do not have an expression with the value being written.
+   */
+  Expr getValue() {
+    this.asExpr().(VariableAssign).getSource() = result or
+    this.asExpr().(AssignOp) = result or
+    this.asExpr().(PreIncExpr) = result or
+    this.asExpr().(PreDecExpr) = result
+  }
+
+  /** Holds if this write is an initialization of parameter `p`. */
+  predicate isParameterInit(Parameter p) { this = TParamInit(p) }
+
+  /** Gets a textual representation of this write. */
+  string toString() {
+    exists(Parameter p | this = TParamInit(p) and result = p.toString())
+    or
+    result = this.asExpr().toString()
+  }
+
+  /** Gets the location of this write. */
+  Location getLocation() {
+    exists(Parameter p | this = TParamInit(p) and result = p.getLocation())
+    or
+    result = this.asExpr().getLocation()
+  }
+}
+
 /** A type literal. For example, `String.class`. */
 class TypeLiteral extends Expr, @typeliteral {
   /** Gets the access to the type whose class is accessed. */

java/ql/lib/semmle/code/java/controlflow/ControlFlowReachability.qll

@@ -6,11 +6,12 @@ module;
 
 import java
 private import codeql.controlflow.ControlFlowReachability
-private import semmle.code.java.dataflow.SSA as SSA
+private import semmle.code.java.dataflow.SSA
 private import semmle.code.java.controlflow.Guards as Guards
 
 private module ControlFlowInput implements InputSig<Location, ControlFlowNode, BasicBlock> {
   private import java as J
+  import Ssa
 
   AstNode getEnclosingAstNode(ControlFlowNode node) { node.getAstNode() = result }
 
@@ -27,23 +28,6 @@ private module ControlFlowInput implements InputSig<Location, ControlFlowNode, B
 
   class Expr = J::Expr;
 
-  class SourceVariable = SSA::SsaSourceVariable;
-
-  class SsaDefinition = SSA::SsaVariable;
-
-  class SsaExplicitWrite extends SsaDefinition instanceof SSA::SsaExplicitUpdate {
-    Expr getValue() {
-      super.getDefiningExpr().(VariableAssign).getSource() = result or
-      super.getDefiningExpr().(AssignOp) = result
-    }
-  }
-
-  class SsaPhiDefinition = SSA::SsaPhiNode;
-
-  class SsaUncertainWrite extends SsaDefinition instanceof SSA::SsaUncertainImplicitUpdate {
-    SsaDefinition getPriorDefinition() { result = super.getPriorDef() }
-  }
-
   class GuardValue = Guards::GuardValue;
 
   predicate ssaControlsBranchEdge(SsaDefinition def, BasicBlock bb1, BasicBlock bb2, GuardValue v) {

java/ql/lib/semmle/code/java/controlflow/Guards.qll

@@ -141,7 +141,7 @@ private predicate isNonFallThroughPredecessor(SwitchCase sc, ControlFlowNode pre
 
 private module GuardsInput implements SharedGuards::InputSig<Location, ControlFlowNode, BasicBlock> {
   private import java as J
-  private import semmle.code.java.dataflow.internal.BaseSSA
+  private import semmle.code.java.dataflow.internal.BaseSSA as Base
   private import semmle.code.java.dataflow.NullGuards as NullGuards
 
   class NormalExitNode = ControlFlow::NormalExitNode;
@@ -211,10 +211,10 @@ private module GuardsInput implements SharedGuards::InputSig<Location, ControlFl
         f.getInitializer() = NullGuards::baseNotNullExpr()
       )
       or
-      exists(CatchClause cc, LocalVariableDeclExpr decl, BaseSsaUpdate v |
+      exists(CatchClause cc, LocalVariableDeclExpr decl, Base::SsaExplicitWrite v |
         decl = cc.getVariable() and
         decl = v.getDefiningExpr() and
-        this = v.getAUse()
+        this = v.getARead()
       )
     }
   }
@@ -407,61 +407,17 @@ private module LogicInputCommon {
 }
 
 private module LogicInput_v1 implements GuardsImpl::LogicInputSig {
-  private import semmle.code.java.dataflow.internal.BaseSSA
-
-  final private class FinalBaseSsaVariable = BaseSsaVariable;
-
-  class SsaDefinition extends FinalBaseSsaVariable {
-    GuardsInput::Expr getARead() { result = this.getAUse() }
-  }
-
-  class SsaExplicitWrite extends SsaDefinition instanceof BaseSsaUpdate {
-    GuardsInput::Expr getValue() {
-      super.getDefiningExpr().(VariableAssign).getSource() = result or
-      super.getDefiningExpr().(AssignOp) = result
-    }
-  }
-
-  class SsaPhiDefinition extends SsaDefinition instanceof BaseSsaPhiNode {
-    predicate hasInputFromBlock(SsaDefinition inp, BasicBlock bb) {
-      super.hasInputFromBlock(inp, bb)
-    }
-  }
-
-  class SsaParameterInit extends SsaDefinition instanceof BaseSsaImplicitInit {
-    Parameter getParameter() { super.isParameterDefinition(result) }
-  }
+  private import semmle.code.java.dataflow.internal.BaseSSA as Base
+  import Base::Ssa
 
   predicate additionalNullCheck = LogicInputCommon::additionalNullCheck/4;
 
   predicate additionalImpliesStep = LogicInputCommon::additionalImpliesStep/4;
 }
 
 private module LogicInput_v2 implements GuardsImpl::LogicInputSig {
-  private import semmle.code.java.dataflow.SSA as SSA
-
-  final private class FinalSsaVariable = SSA::SsaVariable;
-
-  class SsaDefinition extends FinalSsaVariable {
-    GuardsInput::Expr getARead() { result = this.getAUse() }
-  }
-
-  class SsaExplicitWrite extends SsaDefinition instanceof SSA::SsaExplicitUpdate {
-    GuardsInput::Expr getValue() {
-      super.getDefiningExpr().(VariableAssign).getSource() = result or
-      super.getDefiningExpr().(AssignOp) = result
-    }
-  }
-
-  class SsaPhiDefinition extends SsaDefinition instanceof SSA::SsaPhiNode {
-    predicate hasInputFromBlock(SsaDefinition inp, BasicBlock bb) {
-      super.hasInputFromBlock(inp, bb)
-    }
-  }
-
-  class SsaParameterInit extends SsaDefinition instanceof SSA::SsaImplicitInit {
-    Parameter getParameter() { super.isParameterDefinition(result) }
-  }
+  private import semmle.code.java.dataflow.SSA
+  import Ssa
 
   predicate additionalNullCheck = LogicInputCommon::additionalNullCheck/4;
 

java/ql/lib/semmle/code/java/dataflow/DefUse.qll

@@ -34,8 +34,12 @@ predicate useUsePair(VarRead use1, VarRead use2) { adjacentUseUse+(use1, use2) }
  * Other paths may also exist, so the SSA variables in `def` and `use` can be different.
  */
 predicate defUsePair(VariableUpdate def, VarRead use) {
-  exists(SsaVariable v |
-    v.getAUse() = use and v.getAnUltimateDefinition().(SsaExplicitUpdate).getDefiningExpr() = def
+  exists(SsaDefinition v, SsaExplicitWrite write |
+    v.getARead() = use and write.getDefiningExpr() = def
+  |
+    v.getAnUltimateDefinition() = write
+    or
+    v.(SsaCapturedDefinition).getAnUltimateCapturedDefinition() = write
   )
 }
 
@@ -46,7 +50,9 @@ predicate defUsePair(VariableUpdate def, VarRead use) {
  * Other paths may also exist, so the SSA variables can be different.
  */
 predicate parameterDefUsePair(Parameter p, VarRead use) {
-  exists(SsaVariable v |
-    v.getAUse() = use and v.getAnUltimateDefinition().(SsaImplicitInit).isParameterDefinition(p)
+  exists(SsaDefinition v, SsaParameterInit init | v.getARead() = use and init.getParameter() = p |
+    v.getAnUltimateDefinition() = init
+    or
+    v.(SsaCapturedDefinition).getAnUltimateCapturedDefinition() = init
   )
 }

java/ql/lib/semmle/code/java/dataflow/NullGuards.qll

@@ -26,9 +26,9 @@ Expr enumConstEquality(Expr e, boolean polarity, EnumConstant c) {
 }
 
 /** Gets an instanceof expression of `v` with type `type` */
-InstanceOfExpr instanceofExpr(SsaVariable v, RefType type) {
+InstanceOfExpr instanceofExpr(SsaDefinition v, RefType type) {
   result.getCheckedType() = type and
-  result.getExpr() = v.getAUse()
+  result.getExpr() = v.getARead()
 }
 
 /**
@@ -37,8 +37,8 @@ InstanceOfExpr instanceofExpr(SsaVariable v, RefType type) {
  *
  * Note this includes Kotlin's `==` and `!=` operators, which are value-equality tests.
  */
-EqualityTest varEqualityTestExpr(SsaVariable v1, SsaVariable v2, boolean isEqualExpr) {
-  result.hasOperands(v1.getAUse(), v2.getAUse()) and
+EqualityTest varEqualityTestExpr(SsaDefinition v1, SsaDefinition v2, boolean isEqualExpr) {
+  result.hasOperands(v1.getARead(), v2.getARead()) and
   isEqualExpr = result.polarity()
 }
 
@@ -91,37 +91,37 @@ Expr clearlyNotNullExpr(Expr reason) {
     (reason = r1 or reason = r2)
   )
   or
-  exists(SsaVariable v, boolean branch, VarRead rval, Guard guard |
+  exists(SsaDefinition v, boolean branch, VarRead rval, Guard guard |
     guard = directNullGuard(v, branch, false) and
     guard.controls(rval.getBasicBlock(), branch) and
     reason = guard and
-    rval = v.getAUse() and
+    rval = v.getARead() and
     result = rval and
     not result = baseNotNullExpr()
   )
   or
-  exists(SsaVariable v |
+  exists(SsaDefinition v |
     clearlyNotNull(v, reason) and
-    result = v.getAUse() and
+    result = v.getARead() and
     not result = baseNotNullExpr()
   )
 }
 
 /** Holds if `v` is an SSA variable that is provably not `null`. */
-predicate clearlyNotNull(SsaVariable v, Expr reason) {
+predicate clearlyNotNull(SsaDefinition v, Expr reason) {
   exists(Expr src |
-    src = v.(SsaExplicitUpdate).getDefiningExpr().(VariableAssign).getSource() and
+    src = v.(SsaExplicitWrite).getValue() and
     src = clearlyNotNullExpr(reason)
   )
   or
   exists(CatchClause cc, LocalVariableDeclExpr decl |
     decl = cc.getVariable() and
-    decl = v.(SsaExplicitUpdate).getDefiningExpr() and
+    decl = v.(SsaExplicitWrite).getDefiningExpr() and
     reason = decl
   )
   or
-  exists(SsaVariable captured |
-    v.(SsaImplicitInit).captures(captured) and
+  exists(SsaDefinition captured |
+    v.(SsaCapturedDefinition).captures(captured) and
     clearlyNotNull(captured, reason)
   )
   or
@@ -136,7 +136,7 @@ predicate clearlyNotNull(SsaVariable v, Expr reason) {
 Expr clearlyNotNullExpr() { result = clearlyNotNullExpr(_) }
 
 /** Holds if `v` is an SSA variable that is provably not `null`. */
-predicate clearlyNotNull(SsaVariable v) { clearlyNotNull(v, _) }
+predicate clearlyNotNull(SsaDefinition v) { clearlyNotNull(v, _) }
 
 /**
  * Holds if the evaluation of a call to `m` resulting in the value `branch`
@@ -207,7 +207,7 @@ deprecated Expr basicOrCustomNullGuard(Expr e, boolean branch, boolean isnull) {
  * If `result` evaluates to `branch`, then `v` is guaranteed to be null if `isnull`
  * is true, and non-null if `isnull` is false.
  */
-Expr directNullGuard(SsaVariable v, boolean branch, boolean isnull) {
+Expr directNullGuard(SsaDefinition v, boolean branch, boolean isnull) {
   result = basicNullGuard(sameValue(v, _), branch, isnull)
 }
 
@@ -219,7 +219,7 @@ Expr directNullGuard(SsaVariable v, boolean branch, boolean isnull) {
  * If `result` evaluates to `branch`, then `v` is guaranteed to be null if `isnull`
  * is true, and non-null if `isnull` is false.
  */
-deprecated Guard nullGuard(SsaVariable v, boolean branch, boolean isnull) {
+deprecated Guard nullGuard(SsaDefinition v, boolean branch, boolean isnull) {
   result = directNullGuard(v, branch, isnull)
 }
 
@@ -228,7 +228,9 @@ deprecated Guard nullGuard(SsaVariable v, boolean branch, boolean isnull) {
  * from `bb1` to `bb2` implies that `v` is guaranteed to be null if `isnull` is
  * true, and non-null if `isnull` is false.
  */
-predicate nullGuardControlsBranchEdge(SsaVariable v, boolean isnull, BasicBlock bb1, BasicBlock bb2) {
+predicate nullGuardControlsBranchEdge(
+  SsaDefinition v, boolean isnull, BasicBlock bb1, BasicBlock bb2
+) {
   exists(GuardValue gv |
     Guards_v3::ssaControlsBranchEdge(v, bb1, bb2, gv) and
     gv.isNullness(isnull)
@@ -240,7 +242,7 @@ predicate nullGuardControlsBranchEdge(SsaVariable v, boolean isnull, BasicBlock
  * `bb` `v` is guaranteed to be null if `isnull` is true, and non-null if
  * `isnull` is false.
  */
-predicate nullGuardControls(SsaVariable v, boolean isnull, BasicBlock bb) {
+predicate nullGuardControls(SsaDefinition v, boolean isnull, BasicBlock bb) {
   exists(GuardValue gv |
     Guards_v3::ssaControls(v, bb, gv) and
     gv.isNullness(isnull)
@@ -263,6 +265,6 @@ predicate guardSuggestsExprMaybeNull(Expr guard, Expr e) {
 /**
  * Holds if `guard` is a guard expression that suggests that `v` might be null.
  */
-predicate guardSuggestsVarMaybeNull(Expr guard, SsaVariable v) {
+predicate guardSuggestsVarMaybeNull(Expr guard, SsaDefinition v) {
   guardSuggestsExprMaybeNull(guard, sameValue(v, _))
 }