improve diagnostics

Author: jturcotti

lib/SILOptimizer/Mandatory/SendNonSendable.cpp

@@ -527,6 +527,20 @@ class PartitionAnalysis {
     }
   }
 
+  // track the AST exprs that have already had diagnostics emitted about
+  llvm::DenseSet<Expr *> emittedExprs;
+
+  // check if a diagnostic has already been emitted about expr, only
+  // returns true false for each expr
+  bool hasBeenEmitted(Expr *expr) {
+    if (auto castExpr = dyn_cast<ImplicitConversionExpr>(expr))
+      return hasBeenEmitted(castExpr->getSubExpr());
+
+    if (emittedExprs.contains(expr)) return true;
+    emittedExprs.insert(expr);
+    return false;
+  }
+
   // once the fixpoint has been solved for, run one more pass over each basic
   // block, reporting any failures due to requiring consumed regions in the
   // fixpoint state
@@ -538,9 +552,12 @@ class PartitionAnalysis {
         SILInstruction *sourceInstr = partitionOp.getSourceInst();
         assert(sourceInstr && "PartitionOps used in PartitionAnalysis should "
                               "always have been generated with a sourceInst");
+        Expr *expr = sourceInstr->getLoc().getAsASTNode<Expr>();
+        assert(expr && "PartitionOp's source location should correspond to"
+                       "an AST node");
+        if (hasBeenEmitted(expr)) return;
         function->getASTContext().Diags.diagnose(
-            sourceInstr->getLoc().getSourceLoc(),
-            diag::send_non_sendable, consumedVal);
+            expr->getLoc(), diag::send_non_sendable, consumedVal);
       });
     }
   }