Add test for the unused const warning

test/aeso_compiler_tests.erl

@@ -289,7 +289,9 @@ warnings() ->
       <<?PosW(60, 5)
         "The function `dec` is defined but never used.">>,
       <<?PosW(73, 9)
-        "The definition of `const` shadows an older definition at line 70, column 3.">>
+        "The definition of `const` shadows an older definition at line 70, column 3.">>,
+      <<?PosW(84, 7)
+        "The constant `c` is defined but never used.">>
      ]).
 
 failing_contracts() ->
@@ -860,7 +862,9 @@ failing_contracts() ->
                    <<?Pos(60, 5)
                      "The function `dec` is defined but never used.">>,
                    <<?Pos(73, 9)
-                     "The definition of `const` shadows an older definition at line 70, column 3.">>
+                     "The definition of `const` shadows an older definition at line 70, column 3.">>,
+                   <<?Pos(84, 7)
+                     "The constant `c` is defined but never used.">>
                   ])
     , ?TYPE_ERROR(polymorphism_contract_interface_recursive,
                   [<<?Pos(1,24)

test/contracts/warnings.aes

@@ -72,3 +72,17 @@ namespace ShadowingConst =
   function f() =
     let const = 2
     const
+
+namespace UnusedConstNamespace =
+  // No warnings should be shown even though const is not used
+  let const = 1
+
+contract UnusedConstContract =
+  // Only `c` should show a warning because it is never used in the contract
+  let a = 1
+  let b = 2
+  let c = 3
+
+  entrypoint f() =
+    // Both normal access and qualified access should prevent the unused const warning
+    a + UnusedConstContract.b