Add type inference for functions without OutputType attribute and anonymous functions (#21127)

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

@@ -650,8 +650,10 @@ Describe "Type inference Tests" -tags "CI" {
     }
 
     It "Infers type from variable with AllowSafeEval" {
-        function Hide-GetProcess { Get-Process }
-        $p = Hide-GetProcess
+        # Invoke-Expression is used to "hide" Get-Process from the type inference.
+        # If the typeinference code is updated to handle Invoke-Expression, this test will need to find some other way to set $p
+        # so that the type inference can't figure it out without evaluating the variable value
+        $p = Invoke-Expression -Command 'Get-Process'
         $res = [AstTypeInference]::InferTypeOf( { $p }.Ast, [TypeInferenceRuntimePermissions]::AllowSafeEval)
         $res.Name | Should -Be 'System.Diagnostics.Process'
     }
@@ -1492,6 +1494,17 @@ Describe "Type inference Tests" -tags "CI" {
         $null = [AstTypeInference]::InferTypeOf($FoundAst)
     }
 
+    It 'Should infer output from anonymous function' {
+        $res = [AstTypeInference]::InferTypeOf( { & {"Hello"} }.Ast)
+        $res.Name | Should -Be 'System.String'
+    }
+
+    It 'Should infer output from function without OutputType attribute' {
+        function MyHello{"Hello"}
+        $res = [AstTypeInference]::InferTypeOf( { MyHello }.Ast)
+        $res.Name | Should -Be 'System.String'
+    }
+
     It 'Infers type of command with all streams redirected to Success stream' {
         $res = [AstTypeInference]::InferTypeOf( { Get-PSDrive *>&1 }.Ast)
         $ExpectedTypeNames = @(