[ConstraintSystem] Track invalid function builder bodies to avoid duplicate diagnostics

Author: xedin

lib/Sema/BuilderTransform.cpp

@@ -1655,6 +1655,13 @@ ConstraintSystem::matchFunctionBuilder(
   assert(builder && "Bad function builder type");
   assert(builder->getAttrs().hasAttribute<FunctionBuilderAttr>());
 
+  if (InvalidFunctionBuilderBodies.count(fn)) {
+    (void)recordFix(
+        IgnoreInvalidFunctionBuilderBody::duringConstraintGeneration(
+            *this, getConstraintLocator(fn.getBody())));
+    return getTypeMatchSuccess();
+  }
+
   // Pre-check the body: pre-check any expressions in it and look
   // for return statements.
   auto request =
@@ -1720,6 +1727,8 @@ ConstraintSystem::matchFunctionBuilder(
       return getTypeMatchFailure(locator);
 
     if (transaction.hasErrors()) {
+      InvalidFunctionBuilderBodies.insert(fn);
+
       if (recordFix(
               IgnoreInvalidFunctionBuilderBody::duringConstraintGeneration(
                   *this, getConstraintLocator(fn.getBody()))))

lib/Sema/ConstraintSystem.h

@@ -2025,6 +2025,13 @@ class ConstraintSystem {
   /// from declared parameters/result and body.
   llvm::MapVector<const ClosureExpr *, FunctionType *> ClosureTypes;
 
+  /// This is a *global* list of all function builder bodies that have
+  /// been determined to be incorrect by failing constraint generation.
+  ///
+  /// Tracking this information is useful to avoid producing duplicate
+  /// diagnostics when function builder has multiple overloads.
+  llvm::SmallDenseSet<AnyFunctionRef> InvalidFunctionBuilderBodies;
+
   /// Maps node types used within all portions of the constraint
   /// system, instead of directly using the types on the
   /// nodes themselves. This allows us to typecheck and