Remove @errorexpr from the dbscheme (use @badexpr)

Author: owen-mc

go/downgrades/a58b81b1b4c4cccc8ca11731c1db86622f33af57/go.dbscheme

@@ -0,0 +1,2 @@
+description: Delete @errorexpr - @badexpr should be used instead
+compatibility: full

go/downgrades/a58b81b1b4c4cccc8ca11731c1db86622f33af57/old.dbscheme

@@ -521,9 +521,6 @@ var ChanTypeExprs = map[ast.ChanDir]*BranchType{
 	ast.SEND | ast.RECV: ExprKind.NewBranch("@sendrcvchantypeexpr", ChanTypeExpr),
 }
 
-// ErrorExpr is an AST node type that is not used anywhere
-var ErrorExpr = ExprKind.NewBranch("@errorexpr")
-
 // StmtKind is a case type for distinguishing different kinds of statement AST nodes
 var StmtKind = NewCaseType(StmtType, "kind")
 

go/downgrades/a58b81b1b4c4cccc8ca11731c1db86622f33af57/upgrade.properties

@@ -319,8 +319,7 @@ case @expr.kind of
 | 51 = @andnotexpr
 | 52 = @sendchantypeexpr
 | 53 = @recvchantypeexpr
-| 54 = @sendrcvchantypeexpr
-| 55 = @errorexpr;
+| 54 = @sendrcvchantypeexpr;
 
 @basiclit = @intlit | @floatlit | @imaglit | @charlit | @stringlit;
 

go/extractor/dbscheme/tables.go

@@ -0,0 +1,28 @@
+class Expr_ extends @expr {
+  string toString() { result = "Expr" }
+}
+
+class ExprParent_ extends @exprparent {
+  string toString() { result = "ExprParent" }
+}
+
+/**
+ * The last index, 55 (errorexpr), has been deleted. Index 0 (badexpr) should
+ * be used instead.
+ */
+bindingset[old_index]
+int new_index(int old_index) {
+  if old_index = 55
+  then result = 0 // badexpr
+  else result = old_index
+}
+
+// The schema for exprs is:
+//
+// exprs(unique int id: @expr,
+//     int kind: int ref,
+//     int parent: @exprparent ref,
+//     int idx: int ref);
+from Expr_ expr, int new_kind, ExprParent_ parent, int idx, int old_kind
+where exprs(expr, old_kind, parent, idx) and new_kind = new_index(old_kind)
+select expr, new_kind, parent, idx