10 files changed, 78 insertions, 36 deletions
diff --git a/source/slang/diagnostic-defs.h b/source/slang/diagnostic-defs.h
index bae501a3c..f8b09a196 100644
--- a/source/slang/diagnostic-defs.h
+++ b/source/slang/diagnostic-defs.h
@@ -257,6 +257,8 @@ DIAGNOSTIC(38102, Error, accessorMustBeInsideSubscriptOrProperty, "an accessor d
 DIAGNOSTIC(38020, Error, mismatchEntryPointTypeArgument, "expecting $0 entry-point type arguments, provided $1.")
 DIAGNOSTIC(38021, Error, typeArgumentDoesNotConformToInterface, "type argument `$1` for generic parameter `$0` does not conform to interface `$1`.")
 
+DIAGNOSTIC(38200, Error, recursiveModuleImport, "module `$0` recursively imports itself")
+
 //
 // 4xxxx - IL code generation.
 //
diff --git a/source/slang/slang.cpp b/source/slang/slang.cpp
index e4bf251fc..773b1dd09 100644
--- a/source/slang/slang.cpp
+++ b/source/slang/slang.cpp
@@ -499,16 +499,31 @@ void CompileRequest::loadParsedModule(
     Name*                                   name,
     String const&                           path)
 {
+    // Note: we add the loaded module to our name->module listing
+    // before doing semantic checking, so that if it tries to
+    // recursively `import` itself, we can detect it.
+    RefPtr<LoadedModule> loadedModule = new LoadedModule();
+    mapPathToLoadedModule.Add(path, loadedModule);
+    mapNameToLoadedModules.Add(name, loadedModule);
+
+    int errorCountBefore = mSink.GetErrorCount();
     checkTranslationUnit(translationUnit.Ptr());
+    int errorCountAfter = mSink.GetErrorCount();
 
     RefPtr<ModuleDecl> moduleDecl = translationUnit->SyntaxNode;
-
-    RefPtr<LoadedModule> loadedModule = new LoadedModule();
     loadedModule->moduleDecl = moduleDecl;
-    loadedModule->irModule = generateIRForTranslationUnit(translationUnit);
 
-    mapPathToLoadedModule.Add(path, loadedModule);
-    mapNameToLoadedModules.Add(name, loadedModule);
+    if (errorCountAfter != errorCountBefore)
+    {
+        // There must have been an error in the loaded module.
+    }
+    else
+    {
+        // If we didn't run into any errors, then try to generate
+        // IR code for the imported module.
+        loadedModule->irModule = generateIRForTranslationUnit(translationUnit);
+    }
+
     loadedModulesList.Add(loadedModule);
 }
 
@@ -591,7 +606,16 @@ RefPtr<ModuleDecl> CompileRequest::findOrImportModule(
     // If so, return it.
     RefPtr<LoadedModule> loadedModule;
     if (mapNameToLoadedModules.TryGetValue(name, loadedModule))
-        return loadedModule->moduleDecl;
+    {
+        if (!loadedModule)
+            return nullptr;
+
+        if (!loadedModule->moduleDecl)
+        {
+            // We seem to be in the middle of loading this module
+            mSink.diagnose(loc, Diagnostics::recursiveModuleImport, name);
+        }
+    }
 
     // Derive a file name for the module, by taking the given
     // identifier, replacing all occurences of `_` with `-`,
diff --git a/tests/bugs/import-with-error-extra.slang b/tests/bugs/import-with-error-extra.slang
new file mode 100644
index 000000000..259f6b5d1
--- /dev/null
+++ b/tests/bugs/import-with-error-extra.slang
@@ -0,0 +1,11 @@
+//TEST_IGNORE_FILE:
+
+// This file exists to be imported.
+//
+// It contains a semantic error that should lead to compilation failure
+// in the module doing the importing.
+
+void broken()
+{
+	int a = b;
+}
diff --git a/tests/bugs/import-with-error.slang b/tests/bugs/import-with-error.slang
new file mode 100644
index 000000000..f50bb1adb
--- /dev/null
+++ b/tests/bugs/import-with-error.slang
@@ -0,0 +1,11 @@
+//TEST:SIMPLE:-use-ir
+
+// Confirm that we correctly issue a diagnostic when
+// we `import` a module that has some errors in it.
+
+import import_with_error_extra;
+
+void main()
+{
+	broken();
+}
diff --git a/tests/bugs/import-with-error.slang.expected b/tests/bugs/import-with-error.slang.expected
new file mode 100644
index 000000000..b71dba0f1
--- /dev/null
+++ b/tests/bugs/import-with-error.slang.expected
@@ -0,0 +1,6 @@
+result code = -1
+standard error = {
+tests/bugs/import-with-error-extra.slang(10): error 30015: undefined identifier 'b'.
+}
+standard output = {
+}
diff --git a/tests/diagnostics/recursive-import-extra.slang b/tests/diagnostics/recursive-import-extra.slang
new file mode 100644
index 000000000..4525346fa
--- /dev/null
+++ b/tests/diagnostics/recursive-import-extra.slang
@@ -0,0 +1,6 @@
+//TEST_IGNORE_FILE:
+
+// This file creates an `import` loop with
+// `recursive-import.slang`
+
+import recursive_import;
diff --git a/tests/diagnostics/recursive-import.slang b/tests/diagnostics/recursive-import.slang
new file mode 100644
index 000000000..ff74025f8
--- /dev/null
+++ b/tests/diagnostics/recursive-import.slang
@@ -0,0 +1,6 @@
+//TEST:SIMPLE:
+
+// A file that recursively imports itself
+// (including transitive cases) should be diagnosed.
+
+import recursive_import_extra;
diff --git a/tests/diagnostics/recursive-import.slang.expected b/tests/diagnostics/recursive-import.slang.expected
new file mode 100644
index 000000000..ad5cf1975
--- /dev/null
+++ b/tests/diagnostics/recursive-import.slang.expected
@@ -0,0 +1,6 @@
+result code = -1
+standard error = {
+tests/diagnostics/recursive-import.slang(6): error 38200: module `recursive_import_extra` recursively imports itself
+}
+standard output = {
+}
diff --git a/tests/preprocessor/import.hlsl b/tests/preprocessor/import.hlsl
deleted file mode 100644
index f0618a667..000000000
--- a/tests/preprocessor/import.hlsl
+++ /dev/null
@@ -1,18 +0,0 @@
-//TEST:SIMPLE:-target none -profile vs_5_0
-
-// Confirm that `#import` interacts with preprocessor as expected
-
-// Here is a macro that flows from parent to child file
-#define FOO float
-
-// Here we import the child file
-#import "import.slang.h"
-
-// Here we use a macro that flows the other way (child->parent)
-BAR g( FOO x ) { return f(x); }
-
-// Here we confirm that importing the file again is a no-op
-#import "import.slang.h"
-
-void main()
-{}
diff --git a/tests/preprocessor/import.slang.h b/tests/preprocessor/import.slang.h
deleted file mode 100644
index a97a199f0..000000000
--- a/tests/preprocessor/import.slang.h
+++ /dev/null
@@ -1,12 +0,0 @@
-// Confirm that `#import` interacts with preprocessor as expected
-
-// We add a guard to ensure that this file isn't imported more than once
-#ifdef BAR
-#error File imported more than one!
-#endif
-
-// Here we use a macro from the parent file
-FOO f( FOO y ) { return y; }
-
-// Here is a macro that flows from child to parent
-#define BAR float