[CodeCompletion] Don’t crash if constructors in member lookup have an error type

lib/Sema/CSSimplify.cpp

@@ -9171,8 +9171,12 @@ performMemberLookup(ConstraintKind constraintKind, DeclNameRef memberName,
 
       // Only try and favor monomorphic unary initializers.
       if (!ctor->isGenericContext()) {
+        if (!ctor->getMethodInterfaceType()->hasError()) {
+          // The constructor might have an error type because we don't skip
+          // invalid decls for code completion
           auto args = ctor->getMethodInterfaceType()
-                        ->castTo<FunctionType>()->getParams();
+                          ->castTo<FunctionType>()
+                          ->getParams();
           if (args.size() == 1 && !args[0].hasLabel() &&
               args[0].getPlainType()->isEqual(favoredType)) {
             if (!isDeclUnavailable(decl, memberLocator))
@@ -9180,6 +9184,7 @@ performMemberLookup(ConstraintKind constraintKind, DeclNameRef memberName,
           }
         }
       }
+    }
 
     const auto isUnsupportedExistentialMemberAccess = [&] {
       // We may not be able to derive a well defined type for an existential

validation-test/IDE/crashers_2_fixed/0037-constructor-with-error-type.swift

@@ -0,0 +1,12 @@
+// Make sure we don't crash
+// RUN: %target-swift-ide-test -code-completion -source-filename %s -code-completion-token COMPLETE
+
+public struct AnyError {
+
+  public init(_ error: Swift.
+
+extension AnyError {
+  public static func error(from error: Error) -> AnyError {
+    return AnyError(error)#^COMPLETE^#
+  }
+}