LSP test: Minor refactoring and better exception reporting

test/libsolidity/lsp/didOpen_with_import.sol

@@ -8,5 +8,6 @@ contract C
     function f(uint a, uint b) public pure returns (uint)
     {
         return Lib.add(2 * a, b);
+        //     ^^^^^^^ @diagnostics
     }
 }

test/libsolidity/lsp/lib.sol

@@ -23,13 +23,16 @@ enum Color {
 library Lib
 {
     function add(uint a, uint b) public pure returns (uint result)
+// ^( @addFunction
     {
         result = a + b;
     }
 
+// ^) @addFunction
     function warningWithUnused() public pure
     {
         uint unused;
+    //  ^^^^^^^^^^^ @diagnostics
     }
 }
 

test/libsolidity/lsp/publish_diagnostics_1.sol

@@ -6,13 +6,16 @@ contract MyContract
     constructor()
     {
         uint unused; // [Warning 2072] Unused local variable.
+   //   ^^^^^^^^^^^ @unusedVariable
     }
 }
 
 contract D
 {
     function main() public payable returns (uint)
+                                       //   ^^^^ @unusedReturnVariable
     {
         MyContract c = new MyContract();
+   //   ^^^^^^^^^^^^ @unusedContractVariable
     }
 }

test/libsolidity/lsp/publish_diagnostics_2.sol

@@ -6,7 +6,9 @@ contract C
     function makeSomeError() public pure returns (uint res)
     {
         uint x = "hi";
+    //  ^^^^^^^^^^^^^ @conversionError
         return;
+     // ^^^^^^^ @argumentsRequired
         res = 2;
     }
 }
@@ -17,5 +19,6 @@ contract D
     {
         C c = new C();
         return c.makeSomeError(2, 3);
+          //   ^^^^^^^^^^^^^^^^^^^^^ @wrongArgumentsCount
     }
 }

test/libsolidity/lsp/publish_diagnostics_3.sol

@@ -6,5 +6,7 @@ abstract contract A {
 }
 
 contract B is A
+// ^( @notAbstract
 {
 }
+// ^) @notAbstract