Adding VariableExpressionAst.GetAssignments() (#155)

Author: James Brundage

Types/VariableExpressionAST/GetAssignments.ps1

@@ -0,0 +1,48 @@
+<#
+.SYNOPSIS
+    Gets assignments of a variable
+.DESCRIPTION
+    Searches the abstract syntax tree for assignments of the variable.
+.EXAMPLE
+    {
+        $x = 1
+        $y = 2
+        $x * $y
+    }.Ast.EndBlock.Statements[-1].PipelineElements[0].Expression.Left.GetAssignments()
+.EXAMPLE
+    {
+        [int]$x, [int]$y = 1, 2
+        $x * $y
+    }.Ast.EndBlock.Statements[-1].PipelineElements[0].Expression.Left.GetAssignments()
+.EXAMPLE
+    {
+        param($x, $y)        
+        $x * $y
+    }.Ast.EndBlock.Statements[-1].PipelineElements[0].Expression.Left.GetAssignments()
+#>
+param()
+
+$astVariableName = "$this"
+$variableFoundAt = @{}
+foreach ($parent in $this.GetLineage()) {
+    $parent.FindAll({
+        param($ast)
+        $IsAssignment = 
+            (
+                $ast -is [Management.Automation.Language.AssignmentStatementAst] -and
+                $ast.Left.Find({
+                    param($leftAst)
+                    $leftAst -is [Management.Automation.Language.VariableExpressionAST] -and
+                    $leftAst.Extent.ToString() -eq $astVariableName
+                }, $false)
+            ) -or (
+                $ast -is [Management.Automation.Language.ParameterAst] -and 
+                $ast.Name.ToString() -eq $astVariableName
+            )
+
+        if ($IsAssignment -and -not $variableFoundAt[$ast.Extent.StartOffset]) {
+            $variableFoundAt[$ast.Extent.StartOffset] = $ast
+            $ast
+        }        
+    }, $false)
+}