Preprocessor: fix `undef` and redefinition (#204)

* Preprocessor: fix `undef` and redefinition

The logic for `undef` directives was failing to suppress macro expansion when reading the name to un-define, and so it wasn't actually working at all. We didn't notice this because we didn't have a test case, and users hadn't tried it.

The logic for `define` had a similar bug, which meant that any attempt to define an already-defined macro would fail with a cryptic error, rather than raising the intended warning.

Test cases have been added for both issues, along with the fixes.

* fixup: add expected output for tests added

1 files changed, 2 insertions, 2 deletions

diff --git a/source/slang/preprocessor.cpp b/source/slang/preprocessor.cpp
index fff3c0fd4..533a81521 100644
--- a/source/slang/preprocessor.cpp
+++ b/source/slang/preprocessor.cpp
@@ -1619,7 +1619,7 @@ static void HandleIncludeDirective(PreprocessorDirectiveContext* context)
 static void HandleDefineDirective(PreprocessorDirectiveContext* context)
 {
     Token nameToken;
-    if (!Expect(context, TokenType::Identifier, Diagnostics::expectedTokenInPreprocessorDirective, &nameToken))
+    if (!ExpectRaw(context, TokenType::Identifier, Diagnostics::expectedTokenInPreprocessorDirective, &nameToken))
         return;
     Name* name = nameToken.getName();
 
@@ -1701,7 +1701,7 @@ static void HandleDefineDirective(PreprocessorDirectiveContext* context)
 static void HandleUndefDirective(PreprocessorDirectiveContext* context)
 {
     Token nameToken;
-    if (!Expect(context, TokenType::Identifier, Diagnostics::expectedTokenInPreprocessorDirective, &nameToken))
+    if (!ExpectRaw(context, TokenType::Identifier, Diagnostics::expectedTokenInPreprocessorDirective, &nameToken))
         return;
     Name* name = nameToken.getName();