Fix erroneous error claiming variable is being used before its declaration (#2958)

* Simplify type of diagnoseImpl

* Show source line for Note diagnostics, opting out of this where appropriate

* Make declared after use diagnostic clearer

* Fix erroneous error claiming variable is being used before its declaration

Closes https://github.com/shader-slang/slang/issues/2936

* Fix build on msvc

---------

Co-authored-by: jsmall-nvidia <jsmall@nvidia.com>

2 files changed, 22 insertions, 32 deletions

diff --git a/source/compiler-core/slang-diagnostic-sink.cpp b/source/compiler-core/slang-diagnostic-sink.cpp
index f360d3cc6..197e9bb64 100644
--- a/source/compiler-core/slang-diagnostic-sink.cpp
+++ b/source/compiler-core/slang-diagnostic-sink.cpp
@@ -75,7 +75,7 @@ SourceLoc getDiagnosticPos(Token const& token)
 }
 
 // Take the format string for a diagnostic message, along with its arguments, and turn it into a
-static void formatDiagnosticMessage(StringBuilder& sb, char const* format, int argCount, DiagnosticArg const* const* args)
+static void formatDiagnosticMessage(StringBuilder& sb, char const* format, int argCount, DiagnosticArg const* args)
 {
     char const* spanBegin = format;
     for(;;)
@@ -116,8 +116,8 @@ static void formatDiagnosticMessage(StringBuilder& sb, char const* format, int a
                 }
                 else
                 {
-                    DiagnosticArg const* arg = args[index];
-                    arg->printFunc(sb, arg->data);
+                    DiagnosticArg const& arg = args[index];
+                    arg.printFunc(sb, arg.data);
                 }
             }
             break;
@@ -459,9 +459,7 @@ static void formatDiagnostic(
         _tokenLengthNoteDiagnostic(sink, sourceView, sourceLoc, sb);
     }
 
-    // We don't don't output source line information if this is a 'note' as a note is extra information for one
-    // of the other main severity types, and so the information should already be output on the initial line
-    if (sourceView && sink->isFlagSet(DiagnosticSink::Flag::SourceLocationLine) && diagnostic.severity != Severity::Note)
+    if (sourceView && sink->isFlagSet(DiagnosticSink::Flag::SourceLocationLine) && diagnostic.loc.isValid())
     {
         _sourceLocationNoteDiagnostic(sink, sourceView, sourceLoc, sb);
     }
@@ -600,7 +598,7 @@ Severity DiagnosticSink::getEffectiveMessageSeverity(DiagnosticInfo const& info)
     return effectiveSeverity;
 }
 
-void DiagnosticSink::diagnoseImpl(SourceLoc const& pos, DiagnosticInfo info, int argCount, DiagnosticArg const* const* args)
+void DiagnosticSink::diagnoseImpl(SourceLoc const& pos, DiagnosticInfo info, int argCount, DiagnosticArg const* args)
 {
     // Override the severity in the 'info' structure to pass it further into formatDiagnostics
     info.severity = getEffectiveMessageSeverity(info);
diff --git a/source/compiler-core/slang-diagnostic-sink.h b/source/compiler-core/slang-diagnostic-sink.h
index ebd43b456..c150de900 100644
--- a/source/compiler-core/slang-diagnostic-sink.h
+++ b/source/compiler-core/slang-diagnostic-sink.h
@@ -162,39 +162,31 @@ public:
         /// Get the total amount of errors that have taken place on this DiagnosticSink
     SLANG_FORCE_INLINE int getErrorCount() { return m_errorCount; }
 
-    void diagnoseDispatch(SourceLoc const& pos, DiagnosticInfo const& info)
-    {
-        diagnoseImpl(pos, info, 0, nullptr);
-    }
-
-    void diagnoseDispatch(SourceLoc const& pos, DiagnosticInfo const& info, DiagnosticArg const& arg0)
+    template<typename P, typename... Args>
+    void diagnose(P const& pos, DiagnosticInfo const& info, Args const&... args )
     {
-        DiagnosticArg const* args[] = { &arg0 };
-        diagnoseImpl(pos, info, 1, args);
+        DiagnosticArg as[] = { DiagnosticArg(args)... };
+        diagnoseImpl(getDiagnosticPos(pos), info, sizeof...(args), as);
     }
 
-    void diagnoseDispatch(SourceLoc const& pos, DiagnosticInfo const& info, DiagnosticArg const& arg0, DiagnosticArg const& arg1)
+    template<typename P>
+    void diagnose(P const& pos, DiagnosticInfo const& info)
     {
-        DiagnosticArg const* args[] = { &arg0, &arg1 };
-        diagnoseImpl(pos, info, 2, args);
+        // MSVC gets upset with the zero sized array above, so overload that case here
+        diagnoseImpl(getDiagnosticPos(pos), info, 0, nullptr);
     }
 
-    void diagnoseDispatch(SourceLoc const& pos, DiagnosticInfo const& info, DiagnosticArg const& arg0, DiagnosticArg const& arg1, DiagnosticArg const& arg2)
+    // Useful for notes on existing diagnostics, where it would be redundant to display the same line again.
+    // (Ideally we would print the error/warning and notes in one call...)
+    template<typename P, typename... Args>
+    void diagnoseWithoutSourceView(P const& pos, DiagnosticInfo const& info, Args const&... args )
     {
-        DiagnosticArg const* args[] = { &arg0, &arg1, &arg2 };
-        diagnoseImpl(pos, info, 3, args);
-    }
+        const auto fs = this->getFlags();
+        this->resetFlag(Flag::SourceLocationLine);
 
-    void diagnoseDispatch(SourceLoc const& pos, DiagnosticInfo const& info, DiagnosticArg const& arg0, DiagnosticArg const& arg1, DiagnosticArg const& arg2, DiagnosticArg const& arg3)
-    {
-        DiagnosticArg const* args[] = { &arg0, &arg1, &arg2, &arg3 };
-        diagnoseImpl(pos, info, 4, args);
-    }
+        diagnose(pos, info, args...);
 
-    template<typename P, typename... Args>
-    void diagnose(P const& pos, DiagnosticInfo const& info, Args const&... args )
-    {
-        diagnoseDispatch(getDiagnosticPos(pos), info, args...);
+        this->setFlags(fs);
     }
 
         // Add a diagnostic with raw text
@@ -267,7 +259,7 @@ public:
     ISlangWriter* writer = nullptr;
 
 protected:
-    void diagnoseImpl(SourceLoc const& pos, DiagnosticInfo info, int argCount, DiagnosticArg const* const* args);
+    void diagnoseImpl(SourceLoc const& pos, DiagnosticInfo info, int argCount, DiagnosticArg const* args);
     void diagnoseImpl(DiagnosticInfo const& info, const UnownedStringSlice& formattedMessage);
 
     Severity getEffectiveMessageSeverity(DiagnosticInfo const& info);