PipeScript

0.2.8

Transpilers/Core/PipeScript.TypeConstraint.psx.ps1

<#
.SYNOPSIS
    Transpiles Type Constraints
.DESCRIPTION
    Transpiles Type Constraints.
    
    A Type Constraint is an AST expression that constrains a value to a particular type
    (many languages call this a type cast).

    If the type name does not exist, and is not [ordered], PipeScript will search for a transpiler and attempt to run it.
#>
[ValidateScript({
    $TypeConstraintAST = $_
    if (-not $_.TypeName) { return $false }
    $isRealType = $_.TypeName.GetReflectionType()
    if ($isRealType) { return $false }
    if ($TypeConstraintAST.TypeName.Name -eq 'ordered') { return $false }
    if ($_.Parent -is [Management.Automation.Language.ParameterAst]) {
        return $true
    }
    return $true
})]
param(
[Parameter(Mandatory,ParameterSetName='ParameterAst',ValueFromPipeline)]
[Management.Automation.Language.TypeConstraintAst]
$TypeConstraintAST
)

process {
    # First, find the script block that this parameter lives within.
    # We may need it to determine any greater context
    $astPointer = $TypeConstraintAST
    $scriptBlockContext =
        do { # do this by walking up the parents
            $astPointer = $astPointer.Parent
        } while ($astPointer -isnot [Management.Automation.Language.ScriptBlockAst]) # until it is a script block AST.

    
    $isRealType = $TypeConstraintAST.TypeName.GetReflectionType()
    if ($isRealType) { return }
    if ($TypeConstraintAST.TypeName.Name -eq 'ordered') {
        return
    }
    try {
        # If the type constraint is a convert expression
        if ($TypeConstraintAST.Parent -is [Management.Automation.Language.ConvertExpressionAst]) {
            $inputObject =
                # And it's child was a script block
                if ($TypeConstraintAST.Parent.Child -is [Management.Automation.Language.ScriptBlockExpressionAst]) {
                    $TypeConstraintAST.Parent.Child.ScriptBlock.AsScriptBlock()
                }
            if ($inputObject) {
                Invoke-PipeScript -TypeConstraint $TypeConstraintAST -InputObject $inputObject |
                    Add-Member SkipUntil $TypeConstraintAST.Parent.Child.Extent.EndOffset -Force -PassThru |
                    Add-Member ToRemove $TypeConstraintAST.Parent.Child -Force -PassThru
            } else {
                Invoke-PipeScript -TypeConstraint $TypeConstraintAST    
            }
        } else {
            Invoke-PipeScript -TypeConstraint $TypeConstraintAST
        }
    } catch {
        $errorInfo = $_
        $PSCmdlet.WriteError($errorInfo)
    }
}