Fix variable type inference precedence (#18691)

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

@@ -2121,11 +2121,6 @@ namespace System.Management.Automation
                 parent = parent.Parent;
             }
 
-            if (parent.Parent is FunctionDefinitionAst)
-            {
-                parent = parent.Parent;
-            }
-
             int startOffset = variableExpressionAst.Extent.StartOffset;
             var targetAsts = (List<Ast>)AstSearcher.FindAll(
                 parent,
@@ -2165,9 +2160,9 @@ namespace System.Management.Automation
 
             // If any of the assignments lhs use a type constraint, then we use that.
             // Otherwise, we use the rhs of the "nearest" assignment
-            foreach (var assignAst in assignAsts)
+            for (int i = assignAsts.Length - 1; i >= 0; i--)
             {
-                if (assignAst.Left is ConvertExpressionAst lhsConvert)
+                if (assignAsts[i].Left is ConvertExpressionAst lhsConvert)
                 {
                     inferredTypes.Add(new PSTypeName(lhsConvert.Type.TypeName));
                     return;
@@ -2592,7 +2587,8 @@ namespace System.Management.Automation
             if (parameterAst != null)
             {
                 return variableAstVariablePath.IsUnscopedVariable &&
-                       parameterAst.Name.VariablePath.UnqualifiedPath.Equals(variableAstVariablePath.UnqualifiedPath, StringComparison.OrdinalIgnoreCase);
+                       parameterAst.Name.VariablePath.UnqualifiedPath.Equals(variableAstVariablePath.UnqualifiedPath, StringComparison.OrdinalIgnoreCase) &&
+                       parameterAst.Parent.Parent.Extent.EndOffset > variableAst.Extent.StartOffset;
             }
 
             if (ast is ForEachStatementAst foreachAst)

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

@@ -1385,6 +1385,24 @@ Describe "Type inference Tests" -tags "CI" {
         $res.Name -join ' ' | Should -Be "System.IO.FileInfo System.IO.DirectoryInfo"
     }
 
+    It 'Infers closest variable type' {
+        $res = [AstTypeInference]::InferTypeOf( { [string]$TestVar = "";[hashtable]$TestVar = @{};$TestVar }.Ast)
+        $res.Name | Select-Object -Last 1 | Should -Be "System.Collections.Hashtable"
+    }
+
+    It 'Infers closest variable type and ignores unrelated param blocks' {
+        $res = [AstTypeInference]::InferTypeOf( {
+        [hashtable]$ParameterName=@{}
+        function Verb-Noun {
+            param
+            (
+                [string]$ParameterName
+            )
+        }
+        $ParameterName }.Ast)
+        $res.Name | Should -Be "System.Collections.Hashtable"
+    }
+
     It 'Infers type of $null after variable assignment' {
         $res = [AstTypeInference]::InferTypeOf( { $null = "Hello";$null }.Ast)
         $res.Count | Should -Be 0