Swift: Add support for overflow assignment operators.

Author: geoffw0

swift/ql/lib/codeql/swift/elements/expr/AssignExpr.qll

@@ -37,6 +37,18 @@ class Assignment extends Expr {
     result = this.(AssignExpr).getSource() or
     result = this.(AssignOperation).getRightOperand()
   }
+
+  /**
+   * Holds if this assignment expression uses an overflow operator, that is,
+   * an operator that truncates overflow rather than reporting an error.
+   * ```
+   * x &+= y
+   * ```
+   */
+  predicate hasOverflowOperator() {
+    this.(AssignOperation).getOperator().getName() =
+      ["&*=(_:_:)", "&+=(_:_:)", "&-=(_:_:)", "&<<=(_:_:)", "&>>=(_:_:)"]
+  }
 }
 
 /**
@@ -95,10 +107,11 @@ abstract private class AssignBitwiseOperationEx extends BinaryExpr { }
  * An addition assignment expression:
  * ```
  * a += b
+ * a &+= b
  * ```
  */
 class AssignAddExpr extends AssignArithmeticOperationEx {
-  AssignAddExpr() { this.getOperator().getName() = "+=(_:_:)" }
+  AssignAddExpr() { this.getOperator().getName() = ["+=(_:_:)", "&+=(_:_:)"] }
 
   override string toString() { result = "... += ..." }
 }
@@ -107,10 +120,11 @@ class AssignAddExpr extends AssignArithmeticOperationEx {
  * A subtraction assignment expression:
  * ```
  * a -= b
+ * a &-= b
  * ```
  */
 class AssignSubExpr extends AssignArithmeticOperationEx {
-  AssignSubExpr() { this.getOperator().getName() = "-=(_:_:)" }
+  AssignSubExpr() { this.getOperator().getName() = ["-=(_:_:)", "&-=(_:_:)"] }
 
   override string toString() { result = "... -= ..." }
 }
@@ -119,10 +133,11 @@ class AssignSubExpr extends AssignArithmeticOperationEx {
  * A multiplication assignment expression:
  * ```
  * a *= b
+ * a &*= b
  * ```
  */
 class AssignMulExpr extends AssignArithmeticOperationEx {
-  AssignMulExpr() { this.getOperator().getName() = "*=(_:_:)" }
+  AssignMulExpr() { this.getOperator().getName() = ["*=(_:_:)", "&*=(_:_:)"] }
 
   override string toString() { result = "... *= ..." }
 }
@@ -155,10 +170,11 @@ class AssignRemExpr extends AssignArithmeticOperationEx {
  * A left-shift assignment expression:
  * ```
  * a <<= b
+ * a &<<= b
  * ```
  */
 class AssignLShiftExpr extends AssignBitwiseOperationEx {
-  AssignLShiftExpr() { this.getOperator().getName() = "<<=(_:_:)" }
+  AssignLShiftExpr() { this.getOperator().getName() = ["<<=(_:_:)", "&<<=(_:_:)"] }
 
   override string toString() { result = "... <<= ..." }
 }
@@ -167,10 +183,11 @@ class AssignLShiftExpr extends AssignBitwiseOperationEx {
  * A right-shift assignment expression:
  * ```
  * a >>= b
+ * a &>>= b
  * ```
  */
 class AssignRShiftExpr extends AssignBitwiseOperationEx {
-  AssignRShiftExpr() { this.getOperator().getName() = ">>=(_:_:)" }
+  AssignRShiftExpr() { this.getOperator().getName() = [">>=(_:_:)", "&>>=(_:_:)"] }
 
   override string toString() { result = "... >>= ..." }
 }

swift/ql/test/library-tests/elements/expr/assignment/assignment.expected

@@ -9,4 +9,9 @@
 | assignment.swift:18:2:18:7 | ... ^= ... | AssignBitwiseOperation, AssignOperation, AssignXorExpr, Assignment | &... | 1 |
 | assignment.swift:19:2:19:8 | ... <<= ... | AssignBitwiseOperation, AssignLShiftExpr, AssignOperation, Assignment | &... | 1 |
 | assignment.swift:20:2:20:8 | ... >>= ... | AssignBitwiseOperation, AssignOperation, AssignRShiftExpr, Assignment | &... | 1 |
+| assignment.swift:23:2:23:8 | ... *= ... | AssignArithmeticOperation, AssignMulExpr, AssignOperation, Assignment, hasOverflowOperator | &... | 1 |
+| assignment.swift:24:2:24:8 | ... += ... | AssignAddExpr, AssignArithmeticOperation, AssignOperation, Assignment, hasOverflowOperator | &... | 1 |
+| assignment.swift:25:2:25:8 | ... -= ... | AssignArithmeticOperation, AssignOperation, AssignSubExpr, Assignment, hasOverflowOperator | &... | 1 |
+| assignment.swift:26:2:26:9 | ... <<= ... | AssignBitwiseOperation, AssignLShiftExpr, AssignOperation, Assignment, hasOverflowOperator | &... | 1 |
+| assignment.swift:27:2:27:9 | ... >>= ... | AssignBitwiseOperation, AssignOperation, AssignRShiftExpr, Assignment, hasOverflowOperator | &... | 1 |
 | assignment.swift:33:2:33:6 |  ... = ... | AssignExpr, Assignment | y | z |

swift/ql/test/library-tests/elements/expr/assignment/assignment.ql

@@ -30,6 +30,8 @@ string describe(Expr e) {
   e instanceof AssignOrExpr and result = "AssignOrExpr"
   or
   e instanceof AssignXorExpr and result = "AssignXorExpr"
+  or 
+  e.(Assignment).hasOverflowOperator() and result = "hasOverflowOperator"
 }
 
 from Assignment e