Improve diagnostics for overlapping/conflicting bindings

Closes #38

- Change overlapping bindings case from error to warning (it is *technically* allowed in HLSL/GLSL)

- Make diagnostic messages for these cases include a note to point at the "other" declaration in each case, so that user can more easily isolate the problem

- Unrelated fix: make sure `slangc` sets up its diagnostic callback *before* parsing command-line options so that error messages output during options parsing will be visible

- Unrelated fix: make sure that formatting for diagnostic messages doesn't print diagnostic ID for notes (all have IDs < 0).
  - Note: eventually I'd like to not print diagnostic IDs at all (I think they are cluttering up our output), but doing that requires touching all the test cases...

1 files changed, 5 insertions, 5 deletions

diff --git a/source/slangc/main.cpp b/source/slangc/main.cpp
index 6fb394cce..da670909d 100644
--- a/source/slangc/main.cpp
+++ b/source/slangc/main.cpp
@@ -34,6 +34,11 @@ int MAIN(int argc, char** argv)
     SlangSession* session = spCreateSession(nullptr);
     SlangCompileRequest* compileRequest = spCreateCompileRequest(session);
 
+    spSetDiagnosticCallback(
+        compileRequest,
+        &diagnosticCallback,
+        nullptr);
+
     spSetCommandLineCompilerMode(compileRequest);
 
     char const* appName = "slangc";
@@ -46,11 +51,6 @@ int MAIN(int argc, char** argv)
         exit(1);
     }
 
-    spSetDiagnosticCallback(
-        compileRequest,
-        &diagnosticCallback,
-        nullptr);
-
     // Invoke the compiler
 
 #ifndef _DEBUG