Fix dead code reachability logic erroneously flagging on unconditional nested rules

Port of https://github.com/google/cel-go/pull/1323

PiperOrigin-RevId: 924956895

Author: l46kok

conformance/testdata/nested_rules_variable_shadowing/config.yaml

@@ -0,0 +1,18 @@
+# Copyright 2026 Google LLC
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#    https://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+name: nested_rules_variable_shadowing
+variables:
+  - name: x
+    type_name: int

conformance/testdata/nested_rules_variable_shadowing/policy.yaml

@@ -0,0 +1,34 @@
+# Copyright 2026 Google LLC
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#    https://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+name: nested_rules_variable_shadowing
+rule:
+  variables:
+    - name: i
+      expression: '1'
+    - name: j
+      expression: '2'
+  match:
+    - condition: "x == 1"
+      rule:
+        variables:
+          - name: i
+            expression: "5"
+        match:
+          - output: "variables.i + variables.j"
+    - condition: "x == 2"
+      rule:
+        match:
+          - output: "variables.i + variables.j"
+    - output: "variables.i + variables.j"

conformance/testdata/nested_rules_variable_shadowing/tests.yaml

@@ -0,0 +1,36 @@
+# Copyright 2026 Google LLC
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#    https://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+description: "Nested rule tests for rule variable shadowing"
+section:
+  - name: "shadowing"
+    tests:
+      - name: "shadowed"
+        input:
+          x:
+            expr: "1"
+        output:
+          expr: "7"
+      - name: "neighbor_rule"
+        input:
+          x:
+            expr: "2"
+        output:
+          expr: "3"
+      - name: "parent_rule"
+        input:
+          x:
+            expr: "3"
+        output:
+          expr: "3"

conformance/testdata/unconditional_rules/config.yaml

@@ -0,0 +1,8 @@
+name: unconditional_rules
+variables:
+  - name: a
+    type_name: bool
+  - name: b
+    type_name: bool
+  - name: c
+    type_name: bool

conformance/testdata/unconditional_rules/policy.yaml

@@ -0,0 +1,30 @@
+# Copyright 2026 Google LLC
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#    https://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+name: unconditional_rules
+rule:
+  match:
+    - condition: "a"
+      rule:
+        match:
+          - rule:
+              match:
+                - condition: "b"
+                  output: "1"
+          - output: "2"
+    - rule:
+        match:
+          - condition: "c"
+            output: "3"
+    - output: "4"

conformance/testdata/unconditional_rules/tests.yaml

@@ -0,0 +1,58 @@
+# Copyright 2026 Google LLC
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#    https://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+description: Unconditional rules propagation conformance tests
+section:
+  - name: "composition"
+    tests:
+      - name: "case_a_true_b_true"
+        input:
+          a:
+            expr: "true"
+          b:
+            expr: "true"
+          c:
+            expr: "true"
+        output:
+          expr: "1"
+      - name: "case_a_true_b_false"
+        input:
+          a:
+            expr: "true"
+          b:
+            expr: "false"
+          c:
+            expr: "true"
+        output:
+          expr: "2"
+      - name: "case_a_false_c_true"
+        input:
+          a:
+            expr: "false"
+          b:
+            expr: "false"
+          c:
+            expr: "true"
+        output:
+          expr: "3"
+      - name: "case_a_false_c_false"
+        input:
+          a:
+            expr: "false"
+          b:
+            expr: "false"
+          c:
+            expr: "false"
+        output:
+          expr: "4"

conformance/testdata/variable_type_propagation/config.yaml

@@ -0,0 +1,18 @@
+# Copyright 2026 Google LLC
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#    https://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+name: variable_type_propagation
+variables:
+  - name: x
+    type_name: int

conformance/testdata/variable_type_propagation/policy.yaml

@@ -0,0 +1,23 @@
+# Copyright 2026 Google LLC
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#    https://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+name: variable_type_propagation
+rule:
+  variables:
+    - name: empty_list
+      expression: '[]'
+    - name: string_list
+      expression: '["foo"]'
+  match:
+    - output: "variables.empty_list + [1]"

conformance/testdata/variable_type_propagation/tests.yaml

@@ -0,0 +1,21 @@
+# Copyright 2026 Google LLC
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#    https://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+description: "Rule demonstrating variable types propagate independently"
+section:
+  - name: "test"
+    tests:
+      - name: "types_agree"
+        output:
+          expr: "[1]"