Merge pull request #22670 from owen-mc/go/fix/impl-field-cfg

Go: fix CFG bug - implicit field selections with depth 0

Author: owen-mc

go/ql/lib/semmle/go/controlflow/ControlFlowGraphImpl.qll

@@ -682,7 +682,7 @@ module CfgImpl {
           e.(Go::PromotedSelector).refersTo(explicitField) and
           baseType.getFieldAtDepth(_, explicitFieldDepth) = explicitField
         |
-          index = explicitFieldDepth - implicitFieldDepth
+          index = explicitFieldDepth - implicitFieldDepth and index > 0
         )
       )
       or
@@ -692,7 +692,8 @@ module CfgImpl {
         baseType = e.(Go::PromotedSelector).getSelectedStructType() and
         e.(Go::PromotedSelector).refersTo(method) and
         baseType.getMethodAtDepth(_, mDepth) = method and
-        index = mDepth - implicitFieldDepth
+        index = mDepth - implicitFieldDepth and
+        index > 0
       |
         method = baseType.getMethodOfEmbedded(implicitField, _, implicitFieldDepth + 1)
         or

go/ql/test/query-tests/RedundantCode/UnreachableStatement/main.go

@@ -186,4 +186,21 @@ func test23() {
 	unreachable() // OK: deliberately unreachable
 }
 
+type (
+	embedded  struct{}
+	recursive struct {
+		*embedded
+		value int
+		*recursive
+	}
+)
+
+func test24(x *recursive) []int {
+	values := []int{0}
+	if x.value != 0 {
+		values = append(values, x.value)
+	}
+	return values // OK: reachable because value is a direct field of recursive
+}
+
 func main() {}