Fix type inference error for empty return statements (PowerShell#18351)

Author: MartinGC94

src/System.Management.Automation/engine/parser/TypeInferenceVisitor.cs

@@ -936,6 +936,11 @@ object ICustomAstVisitor.VisitContinueStatement(ContinueStatementAst continueSta
 
         object ICustomAstVisitor.VisitReturnStatement(ReturnStatementAst returnStatementAst)
         {
+            if (returnStatementAst.Pipeline is null)
+            {
+                return TypeInferenceContext.EmptyPSTypeNameArray;
+            }
+
             return returnStatementAst.Pipeline.Accept(this);
         }
 

test/powershell/engine/Api/TypeInference.Tests.ps1

@@ -796,6 +796,11 @@ Describe "Type inference Tests" -tags "CI" {
         $res.Name | Should -Be 'System.Int32'
     }
 
+    It 'Infers type from empty Return statement' {
+        $res = [AstTypeInference]::InferTypeOf( { return }.Ast)
+        $res.Count | Should -Be 0
+    }
+
     It 'Infers type from New-Object statement' {
         $res = [AstTypeInference]::InferTypeOf( {
                 New-Object -TypeName 'System.Diagnostics.Stopwatch'