`infer_schema!` recursion limit reached while expanding the macro `static_cond`

[maueroats]

Setup

Adapting Diesel demo code to access a small database, I was unable to use infer_schema! on an empty database with six (or more) columns. Using the same database with five columns, infer_schema! works fine.

Versions

• Rust: nightly cargo 0.25.0-nightly (930f9d949 2017-12-05 (same behavior with rust stable)
• Diesel: 1.0.0-beat1
• Database: mysql 5.7
• Operating System linux mint 18.2

Feature Flags

• diesel: mysql
• diesel_codegen: none known/set

Problem Description

Following the getting started document, infer_schema! works fine.

With my own database (which I thought was trivial), infer_schema! fails with the following message:

   Compiling dbdemo v0.1.0 (file:///home/user/Rust/dbdemo)
error: recursion limit reached while expanding the macro `static_cond`
 --> src/schema.rs:1:1
  |
1 | infer_schema!("dotenv:DATABASE_URL");
  | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  |
  = help: consider adding a `#![recursion_limit="128"]` attribute to your crate
  = note: this error originates in a macro outside of the current crate (in Nightly builds, run with -Z external-macro-backtrace for more info)

error: Could not compile `dbdemo`.

To learn more, run the command again with --verbose.

The table in question is an empty table created by the following diesel migration run:

CREATE TABLE stations (
  id INT PRIMARY KEY NOT NULL,
  location TEXT NOT NULL,
  city TEXT NOT NULL,
  dpcapacity INT NOT NULL,
  online TEXT NOT NULL,
  evil TEXT NOT NULL
)

If I omit the last line with evil and do diesel migration redo followed by touching the file with the infer_schema!, then cargo build does not fail. Stopped investigating at this point.

What are you trying to accomplish?

Use Diesel to access a small database.

What is the expected output?

Successful compilation.

What is the actual output?

n/a

Are you seeing any additional errors?

no

Steps to reproduce

See above. Let me know if this is not enough to reproduce.

Note that a diesel print-schema works fine, even though infer_schema! does not.

Checklist

• I have already looked over the issue tracker for similar issues.

[Eijebong]

Do what the compiler tells you, add a #![recursion_limit="128"] attribute to your crate