Avoid messing with prototypes

Author: JordonPhillips

smithy-typescript-codegen/src/main/java/software/amazon/smithy/typescript/codegen/SymbolVisitor.java

@@ -96,9 +96,13 @@ final class SymbolVisitor implements SymbolProvider, ShapeVisitor<Symbol> {
         ReservedWords reservedWords = new ReservedWordsBuilder()
                 .loadWords(TypeScriptCodegenPlugin.class.getResource("reserved-words.txt"))
                 .build();
+        ReservedWords memberReservedWords = new ReservedWordsBuilder()
+                .loadWords(TypeScriptCodegenPlugin.class.getResource("reserved-words-members.txt"))
+                .build();
 
         escaper = ReservedWordSymbolProvider.builder()
                 .nameReservedWords(reservedWords)
+                .memberReservedWords(memberReservedWords)
                 // Only escape words when the symbol has a definition file to
                 // prevent escaping intentional references to built-in types.
                 .escapePredicate((shape, symbol) -> !StringUtils.isEmpty(symbol.getDefinitionFile()))

smithy-typescript-codegen/src/main/resources/software/amazon/smithy/typescript/codegen/reserved-words-members.txt

@@ -0,0 +1,24 @@
+# TypeScript reserved words for members.
+#
+# Smithy's rules around the names of types are already pretty strict and
+# mostly compatible with TypeScript's naming conventions. Furthermore, the
+# code generator will automatically uppercase every instance where a
+# TypeScript type is generated from a Smithy type. This makes the majority
+# of all of the reserved words in TypeScript something that will never be
+# encountered when generating code. However, it's possible that other
+# SymbolProvider implementations could be used that do emit reserved
+# words for identifiers, hence this code is useful as an extra layer of
+# protection.
+#
+# Adding new reserved words to this list could potentially result in a
+# breaking change to previously generated clients, so adding new reserved words
+# is discouraged. Ideally we could have just automatically added an alias for
+# built-in types that conflict with generated types, but, unfortunately, it's
+# not currently possible to alias a built-in TypeScript or JavaScript type.
+#
+# When a reserved word is encountered, this implementation will
+# continue to prefix the word with "_" until it's no longer considered
+# reserved.
+
+# Prevent prototype pollution
+__proto__