Regression in 6.2.0: Contains(...) gives NullReferenceException (works in 6.1.3)

In 6.2.0 a query containing .Contains(…) throws a NullReferenceException when performing .Count() on the query.

For example:

using (var pdc = new DbContext())
{
	var q = pdc.Books.Where(o => o.Title.Contains("search"));
	q.Count();
}

This code works in 6.1.3 but throws the below stacktrace in 6.2.0:

System.NullReferenceException: Object reference not set to an instance of an object
  at System.Linq.Expressions.Compiler.LambdaCompiler.EmitMethodCall (System.Linq.Expressions.Expression obj, System.Reflection.MethodInfo method, System.Linq.Expressions.IArgumentProvider methodCallExpr, System.Linq.Expressions.Compiler.LambdaCompiler+CompilationFlags flags) [0x00002] in <521f3fe476f34ea88748e97b3b984d05>:0 
  at System.Linq.Expressions.Compiler.LambdaCompiler.EmitInvocationExpression (System.Linq.Expressions.Expression expr, System.Linq.Expressions.Compiler.LambdaCompiler+CompilationFlags flags) [0x0002d] in <521f3fe476f34ea88748e97b3b984d05>:0 
  at System.Linq.Expressions.Compiler.LambdaCompiler.EmitExpression (System.Linq.Expressions.Expression node, System.Linq.Expressions.Compiler.LambdaCompiler+CompilationFlags flags) [0x00263] in <521f3fe476f34ea88748e97b3b984d05>:0 
  at System.Linq.Expressions.Compiler.LambdaCompiler.EmitExpression (System.Linq.Expressions.Expression node) [0x00000] in <521f3fe476f34ea88748e97b3b984d05>:0 
  at System.Linq.Expressions.Compiler.LambdaCompiler.EmitInstance (System.Linq.Expressions.Expression instance, System.Type& type) [0x00035] in <521f3fe476f34ea88748e97b3b984d05>:0 
  at System.Linq.Expressions.Compiler.LambdaCompiler.EmitMemberExpression (System.Linq.Expressions.Expression expr) [0x00018] in <521f3fe476f34ea88748e97b3b984d05>:0 
  at System.Linq.Expressions.Compiler.LambdaCompiler.EmitExpression (System.Linq.Expressions.Expression node, System.Linq.Expressions.Compiler.LambdaCompiler+CompilationFlags flags) [0x00288] in <521f3fe476f34ea88748e97b3b984d05>:0 
  at System.Linq.Expressions.Compiler.LambdaCompiler.EmitLambdaBody (System.Linq.Expressions.Compiler.CompilerScope parent, System.Boolean inlined, System.Linq.Expressions.Compiler.LambdaCompiler+CompilationFlags flags) [0x00085] in <521f3fe476f34ea88748e97b3b984d05>:0 
  at System.Linq.Expressions.Compiler.LambdaCompiler.EmitLambdaBody () [0x0001a] in <521f3fe476f34ea88748e97b3b984d05>:0 
  at System.Linq.Expressions.Compiler.LambdaCompiler.Compile (System.Linq.Expressions.LambdaExpression lambda) [0x0000d] in <521f3fe476f34ea88748e97b3b984d05>:0 
  at System.Linq.Expressions.LambdaExpression.Compile (System.Boolean preferInterpretation) [0x00000] in <521f3fe476f34ea88748e97b3b984d05>:0 
  at System.Linq.Expressions.LambdaExpression.Compile () [0x00000] in <521f3fe476f34ea88748e97b3b984d05>:0 
  at System.Data.Entity.Core.Objects.ELinq.QueryParameterExpression.EvaluateParameter (System.Object[] arguments) [0x0008d] in <b7b192e5a05f4f14a14aa0d5b14aeeeb>:0 
  at System.Data.Entity.Core.Objects.ELinq.ELinqQueryState.GetExecutionPlan (System.Nullable`1[T] forMergeOption) [0x002e5] in <b7b192e5a05f4f14a14aa0d5b14aeeeb>:0 
  at System.Data.Entity.Core.Objects.ObjectQuery`1+<>c__DisplayClass7[T].<GetResults>b__6 () [0x0000b] in <b7b192e5a05f4f14a14aa0d5b14aeeeb>:0 
  at System.Data.Entity.Core.Objects.ObjectContext.ExecuteInTransaction[T] (System.Func`1[TResult] func, System.Data.Entity.Infrastructure.IDbExecutionStrategy executionStrategy, System.Boolean startLocalTransaction, System.Boolean releaseConnectionOnSuccess) [0x0008a] in <b7b192e5a05f4f14a14aa0d5b14aeeeb>:0 
  at System.Data.Entity.Core.Objects.ObjectQuery`1+<>c__DisplayClass7[T].<GetResults>b__5 () [0x00033] in <b7b192e5a05f4f14a14aa0d5b14aeeeb>:0 
  at System.Data.Entity.Infrastructure.DefaultExecutionStrategy.Execute[TResult] (System.Func`1[TResult] operation) [0x00000] in <b7b192e5a05f4f14a14aa0d5b14aeeeb>:0 
  at System.Data.Entity.Core.Objects.ObjectQuery`1[T].GetResults (System.Nullable`1[T] forMergeOption) [0x00093] in <b7b192e5a05f4f14a14aa0d5b14aeeeb>:0 
  at System.Data.Entity.Core.Objects.ObjectQuery`1[T].<System.Collections.Generic.IEnumerable<T>.GetEnumerator>b__0 () [0x00000] in <b7b192e5a05f4f14a14aa0d5b14aeeeb>:0 
  at System.Data.Entity.Internal.LazyEnumerator`1[T].MoveNext () [0x00008] in <b7b192e5a05f4f14a14aa0d5b14aeeeb>:0 
  at System.Linq.Enumerable.Single[TSource] (System.Collections.Generic.IEnumerable`1[T] source) [0x0003d] in <521f3fe476f34ea88748e97b3b984d05>:0 
  at System.Data.Entity.Core.Objects.ELinq.ObjectQueryProvider.<GetElementFunction>b__3[TResult] (System.Collections.Generic.IEnumerable`1[T] sequence) [0x00000] in <b7b192e5a05f4f14a14aa0d5b14aeeeb>:0 
  at System.Data.Entity.Core.Objects.ELinq.ObjectQueryProvider.ExecuteSingle[TResult] (System.Collections.Generic.IEnumerable`1[T] query, System.Linq.Expressions.Expression queryRoot) [0x00006] in <b7b192e5a05f4f14a14aa0d5b14aeeeb>:0 
  at System.Data.Entity.Core.Objects.ELinq.ObjectQueryProvider.System.Linq.IQueryProvider.Execute[TResult] (System.Linq.Expressions.Expression expression) [0x00014] in <b7b192e5a05f4f14a14aa0d5b14aeeeb>:0 
  at System.Data.Entity.Internal.Linq.DbQueryProvider.Execute[TResult] (System.Linq.Expressions.Expression expression) [0x00022] in <b7b192e5a05f4f14a14aa0d5b14aeeeb>:0 
  at System.Linq.Queryable.Count[TSource] (System.Linq.IQueryable`1[T] source) [0x0002f] in <521f3fe476f34ea88748e97b3b984d05>:0 

[pascalhaakmat]

Adding .ToList() does not solve the problem at all. The problem happens before that, in the expression evaluator.

This is still a vexing problem. Any other recommendations for a workaround?

[ajcvickers]

Closing this as external as the only repro we have points to it being an issue with the mono expression compiler.