Preview generates errors when SQL blocks are invloved

[mtoy-googly-moogly]

source: orig is table('bigquery:bigquery-public-data.google_cloud_release_notes.release_notes') {
  dimension: custom is 'CUSTOM'
}
query: first100 is orig -> { project: *; limit: 100 }
sql: to_sql is {
  connection: "bigquery"
  select: """
    SELECT *
    FROM (%{ ->first100 }% )
  """
}
source: back_to_malloy is from_sql(to_sql)
query: back_to_malloy -> { project: * }

Running the end query works, clicking "Preview" on "back_to_malloy" gets an error. SQL Blocks sit in the model in a weird way and however preview is generating a model to run the preview query, it is hitting into this problem.

[whscullin]

I've created a branch for malloy (https://github.com/malloydata/malloy/tree/whscullin/bug-97) with a test that replicates the vscode behavior for (hopefully?) easier troubleshooting.