1 files changed, 39 insertions, 8 deletions
diff --git a/source/slang/slang-check-decl.cpp b/source/slang/slang-check-decl.cpp
index 21a16cae5..da2300d8a 100644
--- a/source/slang/slang-check-decl.cpp
+++ b/source/slang/slang-check-decl.cpp
@@ -10589,6 +10589,7 @@ void SemanticsDeclHeaderVisitor::visitIncludeDecl(IncludeDecl* decl)
 
     if (fileDecl->members.getCount() == 0)
         return;
+
     auto firstMember = fileDecl->members[0];
     if (auto moduleDeclaration = as<ModuleDeclarationDecl>(firstMember))
     {
@@ -10610,6 +10611,7 @@ void SemanticsDeclHeaderVisitor::visitIncludeDecl(IncludeDecl* decl)
         auto moduleName = getSimpleModuleName(implementing->moduleNameAndLoc.name);
         auto expectedModuleName = moduleDecl->getName();
         bool shouldSkipDiagnostic = false;
+
         if (moduleDecl->members.getCount())
         {
             if (auto moduleDeclarationDecl = as<ModuleDeclarationDecl>(moduleDecl->members[0]))
@@ -10629,16 +10631,44 @@ void SemanticsDeclHeaderVisitor::visitIncludeDecl(IncludeDecl* decl)
                 }
             }
         }
-        if (!shouldSkipDiagnostic && !moduleName.getUnownedSlice().caseInsensitiveEquals(
-                                         getText(expectedModuleName).getUnownedSlice()))
+
+        if (!shouldSkipDiagnostic)
         {
-            getSink()->diagnose(
-                decl->moduleNameAndLoc.loc,
-                Diagnostics::includedFileDoesNotImplementCurrentModule,
-                expectedModuleName,
-                moduleName);
-            return;
+            // First check for the case when the user has put a file extension
+            // in the include path
+            String moduleNameStr = moduleName.getUnownedSlice();
+            String expectedModuleNameStr = getText(expectedModuleName).getUnownedSlice();
+
+            // Check if module name has a source file extension
+            if (moduleNameStr.endsWith(".slang"))
+            {
+                String normalizedName = moduleNameStr.subString(0, moduleNameStr.getLength() - 6);
+
+                // If the normalized name would match, emit warning but continue
+                if (normalizedName.getUnownedSlice().caseInsensitiveEquals(
+                        expectedModuleNameStr.getUnownedSlice()))
+                {
+                    getSink()->diagnose(
+                        implementing->moduleNameAndLoc.loc,
+                        Diagnostics::moduleImplementationHasFileExtension,
+                        moduleNameStr,
+                        normalizedName);
+                    return;
+                }
+            }
+
+            if (!moduleNameStr.getUnownedSlice().caseInsensitiveEquals(
+                    expectedModuleNameStr.getUnownedSlice()))
+            {
+                getSink()->diagnose(
+                    decl->moduleNameAndLoc.loc,
+                    Diagnostics::includedFileDoesNotImplementCurrentModule,
+                    expectedModuleName,
+                    moduleName);
+                return;
+            }
         }
+
         return;
     }
 
@@ -10648,6 +10678,7 @@ void SemanticsDeclHeaderVisitor::visitIncludeDecl(IncludeDecl* decl)
         name);
 }
 
+
 void SemanticsDeclScopeWiringVisitor::visitImplementingDecl(ImplementingDecl* decl)
 {
     // Don't need to do anything unless we are in a language server context.