C++: Use Opcode::Error for ErrorExpr translation

cpp/ql/src/semmle/code/cpp/ir/implementation/Opcode.qll

@@ -1,6 +1,7 @@
 private newtype TOpcode =
   TNoOp() or
   TUninitialized() or
+  TError() or
   TInitializeParameter() or
   TInitializeThis() or
   TEnterFunction() or
@@ -147,6 +148,7 @@ abstract class BufferAccessOpcode extends MemoryAccessOpcode {}
 module Opcode {
   class NoOp extends Opcode, TNoOp { override final string toString() { result = "NoOp" } }
   class Uninitialized extends MemoryAccessOpcode, TUninitialized { override final string toString() { result = "Uninitialized" } }
+  class Error extends Opcode, TError { override final string toString() { result = "Error" } }
   class InitializeParameter extends MemoryAccessOpcode, TInitializeParameter { override final string toString() { result = "InitializeParameter" } }
   class InitializeThis extends Opcode, TInitializeThis { override final string toString() { result = "InitializeThis" } }
   class EnterFunction extends Opcode, TEnterFunction { override final string toString() { result = "EnterFunction" } }

cpp/ql/src/semmle/code/cpp/ir/implementation/aliased_ssa/Instruction.qll

@@ -702,6 +702,22 @@ class FieldAddressInstruction extends FieldInstruction {
   }
 }
 
+/**
+ * An instruction that produces a well-defined but unknown result and has
+ * unknown side effects, including side effects that are not conservatively
+ * modeled in the SSA graph.
+ *
+ * This type of instruction appears when there is an `ErrorExpr` in the AST,
+ * meaning that the extractor could not understand the expression and therefore
+ * produced a partial AST. Queries that give alerts when some action is _not_
+ * taken may want to ignore any function that contains an `ErrorInstruction`.
+ */
+class ErrorInstruction extends Instruction {
+  ErrorInstruction() {
+    getOpcode() instanceof Opcode::Error
+  }
+}
+
 class UninitializedInstruction extends VariableInstruction {
   UninitializedInstruction() {
     getOpcode() instanceof Opcode::Uninitialized

cpp/ql/src/semmle/code/cpp/ir/implementation/raw/Instruction.qll

@@ -702,6 +702,22 @@ class FieldAddressInstruction extends FieldInstruction {
   }
 }
 
+/**
+ * An instruction that produces a well-defined but unknown result and has
+ * unknown side effects, including side effects that are not conservatively
+ * modeled in the SSA graph.
+ *
+ * This type of instruction appears when there is an `ErrorExpr` in the AST,
+ * meaning that the extractor could not understand the expression and therefore
+ * produced a partial AST. Queries that give alerts when some action is _not_
+ * taken may want to ignore any function that contains an `ErrorInstruction`.
+ */
+class ErrorInstruction extends Instruction {
+  ErrorInstruction() {
+    getOpcode() instanceof Opcode::Error
+  }
+}
+
 class UninitializedInstruction extends VariableInstruction {
   UninitializedInstruction() {
     getOpcode() instanceof Opcode::Uninitialized

cpp/ql/src/semmle/code/cpp/ir/implementation/raw/internal/TranslatedExpr.qll

@@ -2892,6 +2892,6 @@ class TranslatedErrorExpr extends TranslatedSingleInstructionExpr {
   }
 
   override final Opcode getOpcode() {
-    result instanceof Opcode::NoOp
+    result instanceof Opcode::Error
   }
 }

cpp/ql/src/semmle/code/cpp/ir/implementation/unaliased_ssa/Instruction.qll

@@ -702,6 +702,22 @@ class FieldAddressInstruction extends FieldInstruction {
   }
 }
 
+/**
+ * An instruction that produces a well-defined but unknown result and has
+ * unknown side effects, including side effects that are not conservatively
+ * modeled in the SSA graph.
+ *
+ * This type of instruction appears when there is an `ErrorExpr` in the AST,
+ * meaning that the extractor could not understand the expression and therefore
+ * produced a partial AST. Queries that give alerts when some action is _not_
+ * taken may want to ignore any function that contains an `ErrorInstruction`.
+ */
+class ErrorInstruction extends Instruction {
+  ErrorInstruction() {
+    getOpcode() instanceof Opcode::Error
+  }
+}
+
 class UninitializedInstruction extends VariableInstruction {
   UninitializedInstruction() {
     getOpcode() instanceof Opcode::Uninitialized

cpp/ql/test/library-tests/ir/ir/raw_ir.expected

@@ -53,12 +53,12 @@ bad_asts.cpp:
 #   30|     v0_0(void)         = EnterFunction       : 
 #   30|     mu0_1(unknown)     = AliasedDefinition   : 
 #   30|     mu0_2(unknown)     = UnmodeledDefinition : 
-#-----|     r0_3(glval<error>) = NoOp                : 
+#-----|     r0_3(glval<error>) = Error               : 
 #-----|     r0_4(error)        = Load                : &:r0_3, ~mu0_2
 #   32|     r0_5(glval<int>)   = VariableAddress[x]  : 
-#   32|     r0_6(error)        = NoOp                : 
+#   32|     r0_6(error)        = Error               : 
 #   32|     mu0_7(int)         = Store               : &:r0_5, r0_6
-#-----|     r0_8(glval<error>) = NoOp                : 
+#-----|     r0_8(glval<error>) = Error               : 
 #-----|     r0_9(error)        = Load                : &:r0_8, ~mu0_2
 #   33|     r0_10(glval<int>)  = VariableAddress[x]  : 
 #   33|     mu0_11(int)        = Store               : &:r0_10, r0_9