[Sema] Don’t fail constraint generation if a closure contains an ErrorExpr

lib/Sema/CSDiagnostics.cpp

@@ -4926,7 +4926,9 @@ bool MissingArgumentsFailure::diagnoseClosure(const ClosureExpr *closure) {
 
   auto *locator = getLocator();
   if (locator->isForContextualType()) {
-    funcType = getContextualType(locator->getAnchor())->getAs<FunctionType>();
+    if (auto contextualType = getContextualType(locator->getAnchor())) {
+      funcType = contextualType->getAs<FunctionType>();
+    }
   } else if (auto info = getFunctionArgApplyInfo(locator)) {
     auto paramType = info->getParamType();
     // Drop a single layer of optionality because argument could get injected

lib/Sema/CSGen.cpp

@@ -2901,18 +2901,12 @@ namespace {
       struct CollectVarRefs : public ASTWalker {
         ConstraintSystem &cs;
         llvm::SmallPtrSet<TypeVariableType *, 4> varRefs;
-        bool hasErrorExprs = false;
 
         CollectVarRefs(ConstraintSystem &cs) : cs(cs) { }
 
         bool shouldWalkCaptureInitializerExpressions() override { return true; }
 
         PreWalkResult<Expr *> walkToExprPre(Expr *expr) override {
-          // If there are any error expressions in this closure
-          // it wouldn't be possible to infer its type.
-          if (isa<ErrorExpr>(expr))
-            hasErrorExprs = true;
-
           // Retrieve type variables from references to var decls.
           if (auto *declRef = dyn_cast<DeclRefExpr>(expr)) {
             if (auto *varDecl = dyn_cast<VarDecl>(declRef->getDecl())) {
@@ -2954,15 +2948,6 @@ namespace {
 
       closure->walk(collectVarRefs);
 
-      // If walker discovered error expressions, let's fail constraint
-      // generation only if closure is going to participate
-      // in the type-check. This allows us to delay validation of
-      // multi-statement closures until body is opened.
-      if (CS.participatesInInference(closure) &&
-          collectVarRefs.hasErrorExprs) {
-        return Type();
-      }
-
       auto inferredType = inferClosureType(closure);
       if (!inferredType || inferredType->hasError())
         return Type();

test/Constraints/result_builder_diags.swift

@@ -78,7 +78,7 @@ struct TupleBuilderWithoutIf { // expected-note 3{{struct 'TupleBuilderWithoutIf
   static func buildDo<T>(_ value: T) -> T { return value }
 }
 
-func tuplify<T>(_ cond: Bool, @TupleBuilder body: (Bool) -> T) {
+func tuplify<T>(_ cond: Bool, @TupleBuilder body: (Bool) -> T) { // expected-note 2{{in call to function 'tuplify(_:body:)'}}
   print(body(cond))
 }
 
@@ -88,7 +88,7 @@ func tuplifyWithoutIf<T>(_ cond: Bool, @TupleBuilderWithoutIf body: (Bool) -> T)
 
 func testDiags() {
   // For loop
-  tuplify(true) { _ in
+  tuplify(true) { _ in // expected-error {{generic parameter 'T' could not be inferred}}
     17
     for c in name {
     // expected-error@-1 {{cannot find 'name' in scope}}
@@ -464,7 +464,7 @@ struct TestConstraintGenerationErrors {
   }
 
   func buildTupleClosure() {
-    tuplify(true) { _ in
+    tuplify(true) { _ in // expected-error {{generic parameter 'T' could not be inferred}}
       let a = nothing // expected-error {{cannot find 'nothing' in scope}}
       String(nothing) // expected-error {{cannot find 'nothing' in scope}}
     }

test/Parse/recovery.swift

@@ -775,7 +775,7 @@ class r22240342 {
   lazy var xx: Int = {
     foo {  // expected-error {{cannot find 'foo' in scope}}
       let issueView = 42
-      issueView.delegate = 12
+      issueView.delegate = 12 // expected-error {{value of type 'Int' has no member 'delegate'}}
 
     }
     return 42

test/StringProcessing/Sema/regex_builder_fix_import_top_level.swift

@@ -19,11 +19,7 @@ Regex { // expected-error {{regex builder requires the 'RegexBuilder' module be
   /g(h)(i)/
 }
 
-// FIXME: Unfortunately we bail from CSGen if we end up with an ErrorExpr, so
-// don't get a chance to diagnose. We ought to try solving with holes.
-// For now at least, this error should at least hopefully nudge users into
-// realizing they have a missing import.
-Regex {
+Regex { // expected-error {{regex builder requires the 'RegexBuilder' module be imported'}}
   Capture { // expected-error {{cannot find 'Capture' in scope}}
     /abc/
   }

test/stmt/statements.swift

@@ -409,7 +409,7 @@ func matching_pattern_recursion(zs: [Int]) { // expected-note {{'zs' declared he
   }
 
   switch 42 {
-  case {
+  case { // expected-error {{expression pattern of type '() -> ()' cannot match values of type 'Int'}}
       for i in ws { // expected-error {{cannot find 'ws' in scope; did you mean 'zs'?}}
       }
     }: break