Merge pull request #22182 from owen-mc/go/shared-cfg

Go: migrate control flow graph to shared CFG library #2

Author: owen-mc

go/docs/language/learn-ql/go/ast-class-reference.rst

@@ -450,8 +450,6 @@ Miscellaneous
 +----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+--------------------------------------------------------------------------------------------------------+--------------------------------------------------------------------------------------------------------------------+--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
 | ``...``                                                                                                                                                                                                                                                                                                                                                                    | `Ellipsis <https://help.semmle.com/qldoc/go/semmle/go/Expr.qll/type.Expr$Ellipsis.html>`__             |                                                                                                                    |                                                                                                                                                                                                                          |
 +----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+--------------------------------------------------------------------------------------------------------+--------------------------------------------------------------------------------------------------------------------+--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
-| ``(``\ `Expr <https://help.semmle.com/qldoc/go/semmle/go/Expr.qll/type.Expr$Expr.html>`__\ ``)``                                                                                                                                                                                                                                                                           | `ParenExpr <https://help.semmle.com/qldoc/go/semmle/go/Expr.qll/type.Expr$ParenExpr.html>`__           |                                                                                                                    |                                                                                                                                                                                                                          |
-+----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+--------------------------------------------------------------------------------------------------------+--------------------------------------------------------------------------------------------------------------------+--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
 | `Ident <https://help.semmle.com/qldoc/go/semmle/go/Expr.qll/type.Expr$Ident.html>`__\ ``.``\ `Ident <https://help.semmle.com/qldoc/go/semmle/go/Expr.qll/type.Expr$Ident.html>`__                                                                                                                                                                                          | `SelectorExpr <https://help.semmle.com/qldoc/go/semmle/go/Expr.qll/type.Expr$SelectorExpr.html>`__     |                                                                                                                    |                                                                                                                                                                                                                          |
 +----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+--------------------------------------------------------------------------------------------------------+--------------------------------------------------------------------------------------------------------------------+--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
 | `Expr <https://help.semmle.com/qldoc/go/semmle/go/Expr.qll/type.Expr$Expr.html>`__\ ``[``\ `Expr <https://help.semmle.com/qldoc/go/semmle/go/Expr.qll/type.Expr$Expr.html>`__\ ``]``                                                                                                                                                                                       | `IndexExpr <https://help.semmle.com/qldoc/go/semmle/go/Expr.qll/type.Expr$IndexExpr.html>`__           |                                                                                                                    |                                                                                                                                                                                                                          |

go/downgrades/d0e7336b491e35a4c890e0b9755a4030d32ee444/exprs.ql

@@ -0,0 +1,31 @@
+class Expr_ extends @expr {
+  string toString() { result = "Expr" }
+}
+
+class ExprParent_ extends @exprparent {
+  string toString() { result = "ExprParent" }
+}
+
+// The schema for exprs is:
+//
+// exprs(unique int id: @expr,
+//     int kind: int ref,
+//     int parent: @exprparent ref,
+//     int idx: int ref);
+//
+// `@rangeelementexpr` (kind 55) is a synthesized node that groups the loop
+// variables (the key and value) of a `range` statement. To downgrade we remove
+// those nodes and reparent their children (the key and value expressions)
+// directly onto the `range` statement, at the same indices.
+from Expr_ id, int kind, ExprParent_ newparent, int idx
+where
+  exists(ExprParent_ parent | exprs(id, kind, parent, idx) and kind != 55 |
+    // A key or value grouped by a range element node: reparent it onto the
+    // range statement (the range element node's own parent).
+    exists(Expr_ pe | pe = parent and exprs(pe, 55, newparent, _))
+    or
+    // Any other expression keeps its parent unchanged.
+    not exists(Expr_ pe | pe = parent and exprs(pe, 55, _, _)) and
+    newparent = parent
+  )
+select id, kind, newparent, idx