[silgen] [ast] adds param name to diagnostics

Author: Suyash Srijan

include/swift/AST/DiagnosticsSIL.def

@@ -230,8 +230,7 @@ ERROR(guard_body_must_not_fallthrough,none,
       " to exit the scope", ())
 WARNING(unreachable_code,none, "will never be executed", ())
 NOTE(unreachable_code_uninhabited_param_note,none,
-    "the function body will never be executed. remove the function body to dismiss "
-    "the warning", ())
+    "'%0' is uninhabited, so this function body can never be executed", (Identifier))
 NOTE(unreachable_code_branch,none,
      "condition always evaluates to %select{false|true}0", (bool))
 NOTE(call_to_noreturn_note,none,

lib/SILGen/SILGenProlog.cpp

@@ -437,7 +437,7 @@ void SILGenFunction::emitProlog(AnyFunctionRef TheClosure,
         if (auto body = TheClosure.getBody()) {
           if (!body->getElements().empty()) {
             auto &ctx = SGM.M.getASTContext();
-            ctx.Diags.diagnose(body->getStartLoc(), diag::unreachable_code_uninhabited_param_note);
+            ctx.Diags.diagnose(body->getStartLoc(), diag::unreachable_code_uninhabited_param_note, param->getName());
           }
         }
         break;

test/SILGen/functions_uninhabited_param.swift

@@ -2,7 +2,7 @@
 
 //===--- Function declaration with uninhabited parameter type
 
-func foo(baz: Never) -> Int { // expected-note {{the function body will never be executed. remove the function body to dismiss the warning}}
+func foo(baz: Never) -> Int { // expected-note {{'baz' is uninhabited, so this function body can never be executed}}
   print("I can't be called!") // expected-warning{{will never be executed}}
   return 0
 }