feat: type checking in tasks.

[peterhuene]

This commit implements full type checking in tasks.

• Detection of cycles in declarations.
• Type calculations of expressions.
• Type checking of string interpolations.

Workflow type checking is forthcoming.

The following have not been implemented yet, which is required for full 1.2 support:

• support task name (with "task" hidden type) in commands and output declarations.
• support input, output, and hints hidden types in literal expression evaluation.

Additionally, the following changes are included:

• Refactored wdl-analysis to make certain modules public rather than reexporting everything at the root (cleans up the docs a bit).
• Removed DFS space from DocumentGraph as it doesn't need to persist after analysis completes.
• Simplified DocumentScope to contain only whats needed to express names and their types.
• Removed the restriction on Map type representation to allow Union as the key type, which allows type checking to work on a literal {}, which has calculated type Map[Union, Union].
• Fixed basename function to accept a String argument.
• Fixed size function to accept a String argument.
• Removed the span_of function in favor of an AstNode extension trait.
• Changed the call_expr grammar rule to only accept an identifier for the target and not an expression as functions cannot be values in WDL.
• Fixed the CLI tools to not print colors when output is not to a terminal.
• Fixed incorrect parsing of some expressions which required the interior to be non-empty (e.g. foo[] is not a valid index expression).

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[peterhuene]

Opened #164 to track the missing 1.2 features.

[a-frantz]

2 Qs:

1. does merging this bring us up to parity with miniwdl check?
2. I don't see a test for a forward reference, but from my understanding of this code and the spec those should be parseable.

task foo {
    input {
        String arg = if bool then "--arg" else ""
        Boolean bool
    }
    command <<<>>>
}

[claymcleod]

When those are addressed, looks great! Admittedly, there is a ton here, so I may not have caught everything—I sort of ran with the assumption that the approach you took is solid and we can continue to tweak it in the future if need be (mainly because I don't have any concrete experience with better ways to do it).

[peterhuene]

@a-frantz:

does merging this bring us up to parity with miniwdl check?

It does not yet; once I complete workflow type checking, it will.

I don't see a test for a forward reference, but from my understanding of this code and the spec those should be parseable.

I added tests for cycle detection, but you're right, it'd be good to have one that passes without errors with a forward reference. I'll get that added!