Merge pull request #6028 from ethereum/warn-about-unused-struct-array-expr

Detect custom type expressions that have no effect

test/libsolidity/syntaxTests/metaTypes/typeOfContract.sol

@@ -4,3 +4,4 @@ contract Test {
     }
 }
 // ----
+// Warning: (78-88): Statement has no effect.

test/libsolidity/syntaxTests/nameAndTypeResolution/001_name_references.sol

@@ -2,3 +2,5 @@ contract test {
     uint256 variable;
     function f(uint256) public returns (uint out) { f(variable); test; out; }
 }
+// ----
+// Warning: (103-107): Statement has no effect.

test/libsolidity/syntaxTests/nameAndTypeResolution/no_effect_statements.sol

@@ -0,0 +1,16 @@
+contract test {
+ struct s { uint a; uint b;}
+    function f() pure public returns (byte) {
+		s;
+		s(1,2);
+		s[7];
+		uint;
+		uint[7];
+    }
+}
+// ----
+// Warning: (93-94): Statement has no effect.
+// Warning: (98-104): Statement has no effect.
+// Warning: (108-112): Statement has no effect.
+// Warning: (116-120): Statement has no effect.
+// Warning: (124-131): Statement has no effect.