Token calculation fix for Get-Help executed on ScriptBlock for comment help. (#8238)

src/System.Management.Automation/help/HelpCommentsParser.cs

@@ -1154,10 +1154,10 @@ namespace System.Management.Automation
                 //     $sb = { }
                 //     set-item function:foo $sb
                 //     help foo
-                startTokenIndex = savedStartIndex = FirstTokenInExtent(tokens, ast.Extent) - 1;
+                startTokenIndex = savedStartIndex = FirstTokenInExtent(tokens, ast.Extent) + 1;
                 lastTokenIndex = LastTokenInExtent(tokens, ast.Extent, startTokenIndex);
 
-                Diagnostics.Assert(tokens[startTokenIndex + 1].Kind == TokenKind.LCurly,
+                Diagnostics.Assert(tokens[startTokenIndex - 1].Kind == TokenKind.LCurly,
                     "Unexpected first token in script block");
                 Diagnostics.Assert(tokens[lastTokenIndex].Kind == TokenKind.RCurly,
                     "Unexpected last token in script block");

test/powershell/Language/Scripting/ScriptHelp.Tests.ps1

@@ -80,6 +80,57 @@ Describe 'get-help HelpFunc1' -Tags "Feature" {
         #    Useless
         #
         function helpFunc1 {}
+        
+        Set-Item function:dynamicHelpFunc1 -Value {
+            # .SYNOPSIS
+            #
+            #    A relatively useless function.
+            #
+            # .DESCRIPTION
+            #
+            #    A description
+            #
+            #        with indented text and a blank line.
+            #
+            # .NOTES
+            #
+            #    This function is mostly harmless.
+            #
+            # .LINK
+            #
+            #    http://blogs.msdn.com/powershell
+            #
+            # .LINK
+            #
+            #    other commands
+            #
+            # .EXAMPLE
+            #
+            #    If you need an example, you're hopeless.
+            #
+            # .INPUTS
+            #
+            #    Anything you like.
+            #
+            # .OUTPUTS
+            #
+            #    Nothing.
+            #
+            # .COMPONENT
+            #
+            #    Something
+            #
+            # .ROLE
+            #
+            #    CrazyUser
+            #
+            # .FUNCTIONALITY
+            #
+            #    Useless
+            #
+            
+            process { }
+        }
     }
 
     Context 'Get-Help helpFunc1' {
@@ -87,6 +138,11 @@ Describe 'get-help HelpFunc1' -Tags "Feature" {
         TestHelpFunc1 $x
     }
 
+    Context 'Get-Help dynamicHelpFunc1' {
+        $x = get-help dynamicHelpFunc1
+        TestHelpFunc1 $x
+    }
+
     Context 'get-help helpFunc1 -component blah' {
         $x = get-help helpFunc1 -component blah -ErrorAction SilentlyContinue -ErrorVariable e
         TestHelpError $x $e 'HelpNotFound,Microsoft.PowerShell.Commands.GetHelpCommand'