[Diagnostics] Use DeclDescriptiveKind on data flow diagnostics to improve diagnostic message

Author: LucianoPAlmeida

include/swift/AST/DiagnosticsSIL.def

@@ -250,17 +250,30 @@ NOTE(designated_init_c_struct_fix,none,
 
 
 // Control flow diagnostics.
-ERROR(missing_return,none,
-      "missing return in a %select{function|closure}1 expected to return %0",
-      (Type, unsigned))
-ERROR(missing_return_last_expr,none,
-      "missing return in a %select{function|closure}1 expected to return %0; "
+ERROR(missing_return_closure,none,
+      "missing return in a closure expected to return %0",
+      (Type))
+ERROR(missing_return_last_expr_closure,none,
+      "missing return in a closure expected to return %0; "
       "did you mean to return the last expression?",
-      (Type, unsigned))
-ERROR(missing_never_call,none,
-      "%select{function|closure}1 with uninhabited return type %0 is missing "
+      (Type))
+ERROR(missing_never_call_closure,none,
+      "closure with uninhabited return type %0 is missing "
       "call to another never-returning function on all paths",
-      (Type, unsigned))
+      (Type))
+
+ERROR(missing_return_decl,none,
+      "missing return in a %1 expected to return %0",
+      (Type, DescriptiveDeclKind))
+ERROR(missing_return_last_expr_decl,none,
+      "missing return in a %1 expected to return %0; "
+      "did you mean to return the last expression?",
+      (Type, DescriptiveDeclKind))
+ERROR(missing_never_call_decl,none,
+      "%1 with uninhabited return type %0 is missing "
+      "call to another never-returning function on all paths",
+      (Type, DescriptiveDeclKind))
+
 ERROR(guard_body_must_not_fallthrough,none,
       "'guard' body must not fall through, consider using a 'return' or 'throw'"
       " to exit the scope", ())

lib/SILOptimizer/Mandatory/DataflowDiagnostics.cpp

@@ -64,22 +64,38 @@ static void diagnoseMissingReturn(const UnreachableInst *UI,
     auto element = BS->getLastElement();
     if (auto expr = element.dyn_cast<Expr *>()) {
       if (expr->getType()->getRValueType()->isEqual(ResTy)) {
-        Context.Diags.diagnose(
-          expr->getStartLoc(),
-          diag::missing_return_last_expr, ResTy,
-          FLoc.isASTNode<ClosureExpr>() ? 1 : 0)
-        .fixItInsert(expr->getStartLoc(), "return ");
+        if (FLoc.isASTNode<ClosureExpr>()) {
+          Context.Diags
+              .diagnose(expr->getStartLoc(),
+                        diag::missing_return_last_expr_closure, ResTy)
+              .fixItInsert(expr->getStartLoc(), "return ");
+        } else {
+          auto *DC = FLoc.getAsDeclContext();
+          assert(DC && DC->getAsDecl() && "not a declaration?");
+          Context.Diags
+              .diagnose(expr->getStartLoc(),
+                        diag::missing_return_last_expr_decl, ResTy,
+                        DC->getAsDecl()->getDescriptiveKind())
+              .fixItInsert(expr->getStartLoc(), "return ");
+        }
         return;
       }
     }
   }
-  auto diagID = F->isNoReturnFunction(F->getTypeExpansionContext())
-                    ? diag::missing_never_call
-                    : diag::missing_return;
-  diagnose(Context,
-           L.getEndSourceLoc(),
-           diagID, ResTy,
-           FLoc.isASTNode<ClosureExpr>() ? 1 : 0);
+
+  bool isNoReturnFn = F->isNoReturnFunction(F->getTypeExpansionContext());
+  if (FLoc.isASTNode<ClosureExpr>()) {
+    auto diagID = isNoReturnFn ? diag::missing_never_call_closure
+                               : diag::missing_return_closure;
+    diagnose(Context, L.getEndSourceLoc(), diagID, ResTy);
+  } else {
+    auto *DC = FLoc.getAsDeclContext();
+    assert(DC && DC->getAsDecl() && "not a declaration?");
+    auto diagID = isNoReturnFn ? diag::missing_never_call_decl
+                               : diag::missing_return_decl;
+    diagnose(Context, L.getEndSourceLoc(), diagID, ResTy,
+             DC->getAsDecl()->getDescriptiveKind());
+  }
 }
 
 static void diagnoseUnreachable(const SILInstruction *I,