Make using directives inherited in Solidity < 0.7.0

crates/solidity/inputs/language/bindings/rules.msgb

@@ -421,7 +421,15 @@ inherit .lexical_scope
 @contract [ContractDefinition [ContractMembers
     [ContractMember @using [UsingDirective]]
 ]] {
-  edge @contract.lexical_scope -> @using.def
+  if (version-matches "< 0.7.0") {
+    ; In Solidity < 0.7.0 using directives are inherited to derived contracts
+    ; Hence we make @using.def accessible through members, which is accessible
+    ; from derived contract's lexical scopes.
+    edge @contract.members -> @using.def
+  } else {
+    ; For Solidity >= 0.7.0, using directives are restricted to this contract only.
+    edge @contract.lexical_scope -> @using.def
+  }
 }
 
 @contract [ContractDefinition [ContractMembers

crates/solidity/testing/snapshots/bindings_assertions/using/inherited.sol

@@ -0,0 +1,16 @@
+library Lib {
+    function squared(int x) public returns (int) { return x * x; }
+    //       ^def:1
+}
+
+contract Base {
+    using Lib for int;
+}
+
+contract Test is Base {
+    function test(int x) public returns (int) {
+        return x.squared();
+        //       ^ref:1 (< 0.7.0)
+        //       ^ref:! (>= 0.7.0)
+    }
+}