[5.5][Sema] Don’t allow unresolved type variables if LeaveBraceStmtBodyUnchecked is true

lib/IDE/CodeCompletion.cpp

@@ -6593,6 +6593,13 @@ void CodeCompletionCallbacksImpl::doneParsing() {
     if (isDynamicLookup(*ExprType))
       Lookup.setIsDynamicLookup();
     Lookup.getValueExprCompletions(*ExprType, ReferencedDecl.getDecl());
+    /// We set the type of ParsedExpr explicitly above. But we don't want an
+    /// unresolved type in our AST when we type check again for operator
+    /// completions. Remove the type of the ParsedExpr and see if we can come up
+    /// with something more useful based on the the full sequence expression.
+    if (ParsedExpr->getType()->is<UnresolvedType>()) {
+      ParsedExpr->setType(nullptr);
+    }
     Lookup.getOperatorCompletions(ParsedExpr, leadingSequenceExprs);
     Lookup.getPostfixKeywordCompletions(*ExprType, ParsedExpr);
     break;

lib/Sema/TypeCheckStmt.cpp

@@ -1506,7 +1506,6 @@ void StmtChecker::typeCheckASTNode(ASTNode &node) {
       options |= TypeCheckExprFlags::IsDiscarded;
     if (LeaveBraceStmtBodyUnchecked) {
       options |= TypeCheckExprFlags::LeaveClosureBodyUnchecked;
-      options |= TypeCheckExprFlags::AllowUnresolvedTypeVariables;
     }
 
     auto resultTy =

test/IDE/complete_call_arg.swift

@@ -439,7 +439,7 @@ func curry<T1, T2, R>(_ f: @escaping (T1, T2) -> R) -> (T1) -> (T2) -> R {
   return { t1 in { t2 in f(#^NESTED_CLOSURE^#, t2) } }
   // NESTED_CLOSURE: Begin completions
   // FIXME: Should be '/TypeRelation[Invalid]: t2[#T2#]'
-  // NESTED_CLOSURE: Decl[LocalVar]/Local:               t2[#_#]; name=t2
+  // NESTED_CLOSURE: Decl[LocalVar]/Local:               t2; name=t2
   // NESTED_CLOSURE: Decl[LocalVar]/Local:               t1[#T1#]; name=t1
 }
 

validation-test/IDE/crashers_2_fixed/rdar76686564.swift

@@ -0,0 +1,21 @@
+// RUN: %target-swift-ide-test --conforming-methods -code-completion-token=COMPLETE --conforming-methods-expected-types=s:14swift_ide_test10MySequenceP -source-filename %s
+
+protocol MySequence {
+  associatedtype Element
+}
+
+struct Foo<X>: MySequence {
+	typealias Element = X
+}
+
+struct ArgumentDefinition {
+  fileprivate func bashCompletionWords() -> Foo<String> { fatalError() }
+}
+
+func myFlatMap<SegmentOfResult: MySequence>(_ transform: (ArgumentDefinition) -> SegmentOfResult) -> Foo<SegmentOfResult.Element> {
+  fatalError()
+}
+
+func generateArgumentWords() {
+  _ = myFlatMap { $0.#^COMPLETE^# } as Foo<String>
+}