Fix a bug in default ctor synthesizing (#6527)

* Fix a bug in default ctor synthesizing

- This is fix for the implementation bug, when a struct has explicit ctor
  we should not synthesize the default ctor anymore.

- When invoke the synthesized ctor converted from initializer list, we should
  check if the struct is a c-style type if it struct has no synthesized ctor. In this
  case we should report error because it's invalid to use initializer list here.

- The only exception is the unsized array, we still have to fall back to use the
  legacy initializer list logic to initialize the unsized array until we formalize a
  proper solution.

- update test.

6 files changed, 89 insertions, 30 deletions

diff --git a/source/slang/slang-check-conversion.cpp b/source/slang/slang-check-conversion.cpp
index c5cf192ee..1c8846e66 100644
--- a/source/slang/slang-check-conversion.cpp
+++ b/source/slang/slang-check-conversion.cpp
@@ -396,14 +396,35 @@ bool SemanticsVisitor::createInvokeExprForSynthesizedCtor(
 {
     StructDecl* structDecl = isDeclRefTypeOf<StructDecl>(toType).getDecl();
 
-    if (!structDecl || !_getSynthesizedConstructor(
-                           structDecl,
-                           ConstructorDecl::ConstructorFlavor::SynthesizedDefault))
+    if (!structDecl)
         return false;
 
     HashSet<Type*> isVisit;
-    bool isCStyle = isCStyleType(toType, isVisit);
+    bool isCStyle = false;
+    if (!_getSynthesizedConstructor(
+            structDecl,
+            ConstructorDecl::ConstructorFlavor::SynthesizedDefault))
+    {
+        // When a struct has no constructor and it's not a C-style type, the initializer list is
+        // invalid.
+        isCStyle = isCStyleType(toType, isVisit);
+
+        // WAR: We currently still has to allow legacy initializer list for array type until we have
+        // more proper solution for array initialization, so if the right hand side is an array
+        // type, we will not report error and fall-back to legacy initializer list logic.
+        bool isArrayType = as<ArrayExpressionType>(toType) != nullptr;
+        if (!isCStyle && !isArrayType)
+        {
+            getSink()->diagnose(
+                fromInitializerListExpr->loc,
+                Diagnostics::cannotUseInitializerListForType,
+                toType);
+        }
+
+        return false;
+    }
 
+    isCStyle = isCStyleType(toType, isVisit);
     // TODO: This is just a special case for a backwards-compatibility feature
     // for HLSL, this flag will imply that the initializer list is synthesized
     // for a type cast from a literal zero to a 'struct'. In this case, we will fall
diff --git a/source/slang/slang-check-decl.cpp b/source/slang/slang-check-decl.cpp
index 5ee8ba3ef..34143ad75 100644
--- a/source/slang/slang-check-decl.cpp
+++ b/source/slang/slang-check-decl.cpp
@@ -12412,7 +12412,7 @@ bool SemanticsDeclAttributesVisitor::_synthesizeCtorSignature(StructDecl* struct
     // any constructors. see:
     // https://github.com/shader-slang/slang/blob/master/docs/proposals/004-initialization.md#inheritance-initialization
     if (_hasExplicitConstructor(structDecl, true))
-        return false;
+        return true;
 
     // synthesize the signature first.
     // The constructor's visibility level is the same as the struct itself.
diff --git a/tests/initializer-list/explicit-ctor-diagnostic.slang b/tests/initializer-list/explicit-ctor-diagnostic.slang
index a9d0e9858..6ce65c016 100644
--- a/tests/initializer-list/explicit-ctor-diagnostic.slang
+++ b/tests/initializer-list/explicit-ctor-diagnostic.slang
@@ -16,4 +16,7 @@ void test()
 {
    // CHECK: error 39999: too many arguments to call (got 2, expected 1)
    ExplicitCtor e = {1, 2}; // error, no ctor matches initializer list.
+
+   // CHECK: error 39999: not enough arguments to call (got 0, expected 1)
+   ExplicitCtor e1 = {};
 }
diff --git a/tests/initializer-list/struct-inherit-diagnostics.slang b/tests/initializer-list/struct-inherit-diagnostics.slang
new file mode 100644
index 000000000..247431570
--- /dev/null
+++ b/tests/initializer-list/struct-inherit-diagnostics.slang
@@ -0,0 +1,39 @@
+//DIAGNOSTIC_TEST:SIMPLE(filecheck=CHECK):
+
+struct DefaultStruct_base
+{
+    int data0;
+    __init()
+    {
+        data0 = 2;
+    }
+};
+
+struct DefaultStruct1 : DefaultStruct_base
+{
+    int data1 = 1;
+};
+
+struct DefaultStruct2 : DefaultStruct_base
+{
+
+};
+
+[numthreads(1, 1, 1)]
+void computeMain(uint3 dispatchThreadID: SV_DispatchThreadID)
+{
+    //CHECK: error 30504: cannot use initializer list for type 'DefaultStruct1'
+    DefaultStruct1 s1 = {};
+
+    //CHECK: error 30504: cannot use initializer list for type 'DefaultStruct1'
+    DefaultStruct1 s2 = {1};
+
+    //CHECK: error 30504: cannot use initializer list for type 'DefaultStruct1'
+    DefaultStruct1 s3 = {1, 2};
+
+    //CHECK: error 30504: cannot use initializer list for type 'DefaultStruct2'
+    DefaultStruct2 s4 = {};
+
+    //CHECK: error 30504: cannot use initializer list for type 'DefaultStruct2'
+    DefaultStruct2 s5 = {1};
+}
diff --git a/tests/language-feature/struct-field-initializers/struct-field-initializer-inherited.slang b/tests/initializer-list/struct-inherit.slang
index 954a1edbe..71487a74f 100644
--- a/tests/language-feature/struct-field-initializers/struct-field-initializer-inherited.slang
+++ b/tests/initializer-list/struct-inherit.slang
@@ -16,51 +16,42 @@ struct DefaultStruct_base
 
     __init()
     {
-        data1 = 1;
+        data0 = 2;
+        data1 = 3;
     }
 };
+
 struct DefaultStruct1 : DefaultStruct_base
 {
     int data2 = 1;
-};
-struct DefaultStruct2 : DefaultStruct_base
-{
-    int data2 = 1;
     __init()
     {
-        if (data0 != 1)
+        if (data0 == 2)
         {
-            data2 = 0;
+            data2 = 4;
         }
     }
 };
-struct DefaultStruct3 : DefaultStruct_base
+
+struct DefaultStruct2 : DefaultStruct_base
 {
     __init()
     {
     }
 };
-struct DefaultStruct4 : DefaultStruct_base
-{
-};
+
 [numthreads(1, 1, 1)]
 void computeMain(uint3 dispatchThreadID: SV_DispatchThreadID)
 {
-    DefaultStruct1 s1 = {};
+    DefaultStruct1 s1;
     DefaultStruct2 s2;
-    DefaultStruct3 s3;
-    DefaultStruct4 s4 = {};
+
     // BUF: 1
     outputBuffer[0] = true
-        && s1.data0 == 1
-        && s1.data1 == 1
-        && s1.data2 == 1
-        && s2.data0 == 1
-        && s2.data1 == 1
-        && s2.data2 == 1
-        && s3.data0 == 1
-        && s3.data1 == 1
-        && s4.data0 == 1
-        && s4.data1 == 1
+        && s1.data0 == 2
+        && s1.data1 == 3
+        && s1.data2 == 4
+        && s2.data0 == 2
+        && s2.data1 == 3
         ;
 }
diff --git a/tests/language-feature/interfaces/default-construct-conformance.slang b/tests/language-feature/interfaces/default-construct-conformance.slang
index 4a6aed869..b68dc8a4c 100644
--- a/tests/language-feature/interfaces/default-construct-conformance.slang
+++ b/tests/language-feature/interfaces/default-construct-conformance.slang
@@ -33,6 +33,11 @@ struct TestAny : ITest
         value = v;
     }
 
+    __init()
+    {
+        value = 0;
+    }
+
     uint getValue() { return value; }
 }
 
@@ -183,4 +188,4 @@ void testMain(uint3 threadID: SV_DispatchThreadID)
     }
 
     expected[outputIdx++] = uint(-1);
-}
\ No newline at end of file
+}