codegen: fix segfault on numeric literal assigned to a pointer type

.github/workflows/cmake.yml

@@ -56,4 +56,4 @@ jobs:
 
     - name: Test
       working-directory: ${{github.workspace}}/build
-      run: ctest -C ${{env.BUILD_TYPE}} --output-on-failure -E "codegen/pointer.aw"
+      run: ctest -C ${{env.BUILD_TYPE}} --output-on-failure

lang/source/codegen/llvm/backend_llvm.c++

@@ -368,8 +368,12 @@ auto backend_llvm::gen_local(const middle::variable& var) -> llvm::Value*
 
 	auto* alloca = builder.CreateAlloca(get_llvm_type(context, var.type), nullptr, var.name);
 
-	if (var.value)
-		builder.CreateStore(gen(var.value), alloca);
+	if (var.value) {
+		auto* init = gen(var.value);
+		if (!init)
+			return nullptr;
+		builder.CreateStore(init, alloca);
+	}
 
 	return alloca;
 }
@@ -497,6 +501,8 @@ auto backend_llvm::gen(const middle::numeric_literal& expr) -> llvm::Constant*
 			return ConstantFP::get(context, APFloat(APFloat::IEEEsingle(), expr.value));
 		if (type->isDoubleTy())
 			return ConstantFP::get(context, APFloat(APFloat::IEEEdouble(), expr.value));
+		if (type->isPointerTy())
+			return ConstantPointerNull::get(cast<PointerType>(type));
 	}
 	return nullptr;
 }

lang/source/semantic/type_inference.c++

@@ -313,6 +313,11 @@ struct type_inference_visitor
 
 	auto propagate_type(ir::type* type, numeric_literal& expr) -> ir::type*
 	{
+		// Only a literal `0` may stand in for a null pointer; any other
+		// integer literal assigned to a pointer type is a real mismatch.
+		if (get_if<ir::pointer_type>(&type->kind) && expr.value != "0")
+			return error(diag, diagnostic_id::type_mismathch, location(), type->name, std::string("numeric_literal"));
+
 		return (expr.type = type);
 	}
 

test/CMakeLists.txt

@@ -14,10 +14,12 @@ set(TESTS
 	errors/not_allowed_here.aw
 	errors/not_implemented_yet.aw
 	errors/recovery.aw
+	errors/pointer_nonzero_init.aw
 	codegen/array.aw
 	codegen/array_of_structs.aw
 	codegen/chain.aw
 	codegen/function.aw
+	codegen/pointer_null_init.aw
 	modules/main.aw
 )
 
@@ -26,6 +28,7 @@ set(NEGATIVE_TESTS
 	errors/not_allowed_here.aw
 	errors/not_implemented_yet.aw
 	errors/recovery.aw
+	errors/pointer_nonzero_init.aw
 )
 
 set(RUNTIME_TESTS

test/codegen/pointer_null_init.aw

@@ -0,0 +1,4 @@
+func main()
+{
+	var p: int* = 0;
+}

test/errors/pointer_nonzero_init.aw

@@ -0,0 +1,4 @@
+func main()
+{
+	var p: int* = 5;
+}