Merge pull request #56972 from lawnjelly/warn_unused

18 files changed, 35 insertions, 23 deletions

diff --git a/core/math/aabb.h b/core/math/aabb.h
index 2eaaafa27d..3d19410ddf 100644
--- a/core/math/aabb.h
+++ b/core/math/aabb.h
@@ -41,7 +41,7 @@
  */
 class Variant;
 
-class AABB {
+class _NO_DISCARD_ AABB {
 public:
 	Vector3 position;
 	Vector3 size;
diff --git a/core/math/basis.h b/core/math/basis.h
index 709f2cb3cf..802da82089 100644
--- a/core/math/basis.h
+++ b/core/math/basis.h
@@ -34,7 +34,7 @@
 #include "core/math/quaternion.h"
 #include "core/math/vector3.h"
 
-class Basis {
+class _NO_DISCARD_ Basis {
 private:
 	void _set_diagonal(const Vector3 &p_diag);
 
diff --git a/core/math/color.h b/core/math/color.h
index 6c09f7941c..72a4a5f8be 100644
--- a/core/math/color.h
+++ b/core/math/color.h
@@ -34,7 +34,7 @@
 #include "core/math/math_funcs.h"
 #include "core/string/ustring.h"
 
-struct Color {
+struct _NO_DISCARD_ Color {
 	union {
 		struct {
 			float r;
diff --git a/core/math/face3.h b/core/math/face3.h
index 5a34858ccb..3dbbca09e0 100644
--- a/core/math/face3.h
+++ b/core/math/face3.h
@@ -36,7 +36,7 @@
 #include "core/math/transform_3d.h"
 #include "core/math/vector3.h"
 
-class Face3 {
+class _NO_DISCARD_ Face3 {
 public:
 	enum Side {
 		SIDE_OVER,
diff --git a/core/math/plane.h b/core/math/plane.h
index bac946502b..8cb6f62b3b 100644
--- a/core/math/plane.h
+++ b/core/math/plane.h
@@ -35,7 +35,7 @@
 
 class Variant;
 
-class Plane {
+class _NO_DISCARD_ Plane {
 public:
 	Vector3 normal;
 	real_t d = 0;
diff --git a/core/math/quaternion.h b/core/math/quaternion.h
index cf3762e090..2575d7d229 100644
--- a/core/math/quaternion.h
+++ b/core/math/quaternion.h
@@ -36,7 +36,7 @@
 #include "core/math/vector3.h"
 #include "core/string/ustring.h"
 
-class Quaternion {
+class _NO_DISCARD_ Quaternion {
 public:
 	union {
 		struct {
diff --git a/core/math/rect2.h b/core/math/rect2.h
index f34550bef1..4ea24e8f88 100644
--- a/core/math/rect2.h
+++ b/core/math/rect2.h
@@ -35,7 +35,7 @@
 
 struct Transform2D;
 
-struct Rect2 {
+struct _NO_DISCARD_ Rect2 {
 	Point2 position;
 	Size2 size;
 
@@ -363,7 +363,7 @@ struct Rect2 {
 	}
 };
 
-struct Rect2i {
+struct _NO_DISCARD_ Rect2i {
 	Point2i position;
 	Size2i size;
 
diff --git a/core/math/transform_2d.h b/core/math/transform_2d.h
index 752a885eba..6c2d51bd9b 100644
--- a/core/math/transform_2d.h
+++ b/core/math/transform_2d.h
@@ -33,7 +33,7 @@
 
 #include "core/math/rect2.h" // also includes vector2, math_funcs, and ustring
 
-struct Transform2D {
+struct _NO_DISCARD_ Transform2D {
 	// Warning #1: basis of Transform2D is stored differently from Basis. In terms of elements array, the basis matrix looks like "on paper":
 	// M = (elements[0][0] elements[1][0])
 	//     (elements[0][1] elements[1][1])
diff --git a/core/math/transform_3d.h b/core/math/transform_3d.h
index c0ef2ecfc1..c16c278e74 100644
--- a/core/math/transform_3d.h
+++ b/core/math/transform_3d.h
@@ -35,7 +35,7 @@
 #include "core/math/basis.h"
 #include "core/math/plane.h"
 
-class Transform3D {
+class _NO_DISCARD_ Transform3D {
 public:
 	Basis basis;
 	Vector3 origin;
diff --git a/core/math/vector2.h b/core/math/vector2.h
index a340036ac7..af40b9e68d 100644
--- a/core/math/vector2.h
+++ b/core/math/vector2.h
@@ -36,7 +36,7 @@
 
 struct Vector2i;
 
-struct Vector2 {
+struct _NO_DISCARD_ Vector2 {
 	static const int AXIS_COUNT = 2;
 
 	enum Axis {
@@ -284,7 +284,7 @@ typedef Vector2 Point2;
 
 /* INTEGER STUFF */
 
-struct Vector2i {
+struct _NO_DISCARD_ Vector2i {
 	enum Axis {
 		AXIS_X,
 		AXIS_Y,
diff --git a/core/math/vector3.h b/core/math/vector3.h
index d7a72b05a8..b62edef40f 100644
--- a/core/math/vector3.h
+++ b/core/math/vector3.h
@@ -37,7 +37,7 @@
 #include "core/string/ustring.h"
 class Basis;
 
-struct Vector3 {
+struct _NO_DISCARD_ Vector3 {
 	static const int AXIS_COUNT = 3;
 
 	enum Axis {
diff --git a/core/math/vector3i.h b/core/math/vector3i.h
index 1416c98057..1564ee9173 100644
--- a/core/math/vector3i.h
+++ b/core/math/vector3i.h
@@ -35,7 +35,7 @@
 #include "core/string/ustring.h"
 #include "core/typedefs.h"
 
-struct Vector3i {
+struct _NO_DISCARD_ Vector3i {
 	enum Axis {
 		AXIS_X,
 		AXIS_Y,
diff --git a/core/typedefs.h b/core/typedefs.h
index e6034eb375..5929b5123b 100644
--- a/core/typedefs.h
+++ b/core/typedefs.h
@@ -71,6 +71,17 @@
 #endif
 #endif
 
+// No discard allows the compiler to flag warnings if we don't use the return value of functions / classes
+#ifndef _NO_DISCARD_
+#define _NO_DISCARD_ [[nodiscard]]
+#endif
+
+// In some cases _NO_DISCARD_ will get false positives,
+// we can prevent the warning in specific cases by preceding the call with a cast.
+#ifndef _ALLOW_DISCARD_
+#define _ALLOW_DISCARD_ (void)
+#endif
+
 // Windows badly defines a lot of stuff we'll never use. Undefine it.
 #ifdef _WIN32
 #undef min // override standard definition
diff --git a/editor/import/resource_importer_scene.cpp b/editor/import/resource_importer_scene.cpp
index b6624a8cfa..940fc442fb 100644
--- a/editor/import/resource_importer_scene.cpp
+++ b/editor/import/resource_importer_scene.cpp
@@ -1776,7 +1776,8 @@ void ResourceImporterScene::_optimize_track_usage(AnimationPlayer *p_player, Ani
 						if (bone_idx == -1) {
 							continue;
 						}
-						skel->get_bone_pose(bone_idx);
+						// Note that this is using get_bone_pose to update the bone pose cache.
+						_ALLOW_DISCARD_ skel->get_bone_pose(bone_idx);
 						loc = skel->get_bone_pose_position(bone_idx);
 						rot = skel->get_bone_pose_rotation(bone_idx);
 						scale = skel->get_bone_pose_scale(bone_idx);
diff --git a/platform/osx/display_server_osx.mm b/platform/osx/display_server_osx.mm
index e3b4333ec8..60f1eac4b1 100644
--- a/platform/osx/display_server_osx.mm
+++ b/platform/osx/display_server_osx.mm
@@ -316,7 +316,7 @@ static NSCursor *_cursorFromSelector(SEL selector, SEL fallback = nil) {
 		CGPoint lMouseWarpPos = { pointOnScreen.x, CGDisplayBounds(CGMainDisplayID()).size.height - pointOnScreen.y };
 		CGWarpMouseCursorPosition(lMouseWarpPos);
 	} else {
-		_get_mouse_pos(wd, [wd.window_object mouseLocationOutsideOfEventStream]);
+		_ALLOW_DISCARD_ _get_mouse_pos(wd, [wd.window_object mouseLocationOutsideOfEventStream]);
 		Input::get_singleton()->set_mouse_position(wd.mouse_pos);
 	}
 
@@ -1391,7 +1391,7 @@ inline void sendPanEvent(DisplayServer::WindowID window_id, double dx, double dy
 
 	double deltaX, deltaY;
 
-	_get_mouse_pos(wd, [event locationInWindow]);
+	_ALLOW_DISCARD_ _get_mouse_pos(wd, [event locationInWindow]);
 
 	deltaX = [event scrollingDeltaX];
 	deltaY = [event scrollingDeltaY];
@@ -2463,7 +2463,7 @@ void DisplayServerOSX::window_set_position(const Point2i &p_position, WindowID p
 	[wd.window_object setFrameTopLeftPoint:NSMakePoint(position.x - offset.x, position.y - offset.y)];
 
 	_update_window(wd);
-	_get_mouse_pos(wd, [wd.window_object mouseLocationOutsideOfEventStream]);
+	_ALLOW_DISCARD_ _get_mouse_pos(wd, [wd.window_object mouseLocationOutsideOfEventStream]);
 }
 
 void DisplayServerOSX::window_set_max_size(const Size2i p_size, WindowID p_window) {
diff --git a/scene/main/canvas_item.cpp b/scene/main/canvas_item.cpp
index 59d933fa1d..a0916c6291 100644
--- a/scene/main/canvas_item.cpp
+++ b/scene/main/canvas_item.cpp
@@ -1017,8 +1017,8 @@ void CanvasItem::set_notify_transform(bool p_enable) {
 	notify_transform = p_enable;
 
 	if (notify_transform && is_inside_tree()) {
-		//this ensures that invalid globals get resolved, so notifications can be received
-		get_global_transform();
+		// This ensures that invalid globals get resolved, so notifications can be received.
+		_ALLOW_DISCARD_ get_global_transform();
 	}
 }
 
diff --git a/scene/resources/immediate_mesh.cpp b/scene/resources/immediate_mesh.cpp
index b9469803a0..28afef8638 100644
--- a/scene/resources/immediate_mesh.cpp
+++ b/scene/resources/immediate_mesh.cpp
@@ -382,7 +382,7 @@ AABB ImmediateMesh::get_aabb() const {
 		if (i == 0) {
 			aabb = surfaces[i].aabb;
 		} else {
-			aabb.merge(surfaces[i].aabb);
+			aabb = aabb.merge(surfaces[i].aabb);
 		}
 	}
 	return aabb;
diff --git a/servers/rendering/renderer_rd/renderer_scene_render_rd.cpp b/servers/rendering/renderer_rd/renderer_scene_render_rd.cpp
index 33f5a178e0..126f40584a 100644
--- a/servers/rendering/renderer_rd/renderer_scene_render_rd.cpp
+++ b/servers/rendering/renderer_rd/renderer_scene_render_rd.cpp
@@ -514,7 +514,7 @@ Ref<Image> RendererSceneRenderRD::environment_bake_panorama(RID p_env, bool p_ba
 		ambient_color_sky_mix = env->ambient_sky_contribution;
 		const float ambient_energy = env->ambient_light_energy;
 		ambient_color = env->ambient_light;
-		ambient_color.to_linear();
+		ambient_color = ambient_color.to_linear();
 		ambient_color.r *= ambient_energy;
 		ambient_color.g *= ambient_energy;
 		ambient_color.b *= ambient_energy;
@@ -533,7 +533,7 @@ Ref<Image> RendererSceneRenderRD::environment_bake_panorama(RID p_env, bool p_ba
 	} else {
 		const float bg_energy = env->bg_energy;
 		Color panorama_color = ((environment_background == RS::ENV_BG_CLEAR_COLOR) ? storage->get_default_clear_color() : env->bg_color);
-		panorama_color.to_linear();
+		panorama_color = panorama_color.to_linear();
 		panorama_color.r *= bg_energy;
 		panorama_color.g *= bg_energy;
 		panorama_color.b *= bg_energy;