Include parameter type constraints as symbols

Author: andyleejordan

src/PowerShellEditorServices/Services/Symbols/ReferenceTable.cs

@@ -93,7 +93,6 @@ private AstVisitAction AddReference(SymbolReference symbol)
                 return existing;
             });
 
-        return symbol.SymbolType is SymbolType.Parameter
-            ? AstVisitAction.SkipChildren : AstVisitAction.Continue;
+        return AstVisitAction.Continue;
     }
 }

src/PowerShellEditorServices/Services/Symbols/Visitors/SymbolVisitor.cs

@@ -85,6 +85,13 @@ public override AstVisitAction VisitParameter(ParameterAst parameterAst)
 
     public override AstVisitAction VisitVariableExpression(VariableExpressionAst variableExpressionAst)
     {
+        // Parameters are visited earlier, and we don't want to skip their children because we do
+        // want to visit their type constraints.
+        if (variableExpressionAst.Parent is ParameterAst)
+        {
+            return AstVisitAction.Continue;
+        }
+
         // TODO: Consider tracking unscoped variable references only when they declared within
         // the same function definition.
         return _action(new SymbolReference(