Replace impl Into<String> with impl ToString (#302)

* Replace `impl Into<String>` with `impl ToString`

This is something I ran into today. Types that implement
`std::fmt::Display` cannot be passed to functions that take `impl
Into<String>`. You have to call `display_thing.to_string()`. Its a small
thing but would be fixed by instead taking `impl ToString`.

Afaik `impl ToString` is a superset of `impl Into<String>`, unless users
manually implement `Into<String> for T` (or `From<T> for String`) for
their own types. However I think its more common to implement `Display`
as that works with `println` and friends. The main difference is that
`Display::fmt` can return errors but thats also quite rare in my
experience.

I did some testing in a [playground] and seems to work.

[playground]: https://play.rust-lang.org/?version=stable&mode=debug&edition=2018&gist=1111e071f6ae416ae2688d58d2e9b575

* Silence warnings

egui/src/containers/collapsing_header.rs

@@ -148,7 +148,7 @@ impl CollapsingHeader {
     /// If the label is unique and static this is fine,
     /// but if it changes or there are several `CollapsingHeader` with the same title
     /// you need to provide a unique id source with [`Self::id_source`].
-    pub fn new(label: impl Into<String>) -> Self {
+    pub fn new(label: impl ToString) -> Self {
         let label = Label::new(label).text_style(TextStyle::Button).wrap(false);
         let id_source = Id::new(label.text());
         Self {

egui/src/containers/combo_box.rs

@@ -55,8 +55,9 @@ impl ComboBox {
     }
 
     /// What we show as the currently selected value
-    pub fn selected_text(mut self, selected_text: impl Into<String>) -> Self {
+    #[allow(clippy::needless_pass_by_value)]
-        self.selected_text = selected_text.into();
+    pub fn selected_text(mut self, selected_text: impl ToString) -> Self {
+        self.selected_text = selected_text.to_string();
         self
     }
 
@@ -150,7 +151,7 @@ impl ComboBox {
 pub fn combo_box_with_label(
     ui: &mut Ui,
     label: impl Into<Label>,
-    selected: impl Into<String>,
+    selected: impl ToString,
     menu_contents: impl FnOnce(&mut Ui),
 ) -> Response {
     let label = label.into();
@@ -165,10 +166,11 @@ pub fn combo_box_with_label(
     .inner
 }
 
+#[allow(clippy::needless_pass_by_value)]
 fn combo_box(
     ui: &mut Ui,
     button_id: Id,
-    selected: impl Into<String>,
+    selected: impl ToString,
     menu_contents: impl FnOnce(&mut Ui),
 ) -> Response {
     let popup_id = button_id.with("popup");
@@ -181,7 +183,7 @@ fn combo_box(
 
         let galley = ui
             .fonts()
-            .layout_no_wrap(TextStyle::Button, selected.into());
+            .layout_no_wrap(TextStyle::Button, selected.to_string());
 
         let width = galley.size.x + ui.spacing().item_spacing.x + icon_size.x;
         let width = width.at_least(full_minimum_width);

egui/src/containers/popup.rs

@@ -122,7 +122,7 @@ pub fn show_tooltip_at(
 ///     egui::show_tooltip_text(ui.ctx(), egui::Id::new("my_tooltip"), "Helpful text");
 /// }
 /// ```
-pub fn show_tooltip_text(ctx: &CtxRef, id: Id, text: impl Into<String>) {
+pub fn show_tooltip_text(ctx: &CtxRef, id: Id, text: impl ToString) {
     show_tooltip(ctx, id, |ui| {
         ui.add(crate::widgets::Label::new(text));
     })

egui/src/containers/window.rs

@@ -36,8 +36,9 @@ impl<'open> Window<'open> {
     /// The window title is used as a unique [`Id`] and must be unique, and should not change.
     /// This is true even if you disable the title bar with `.title_bar(false)`.
     /// If you need a changing title, you must call `window.id(…)` with a fixed id.
-    pub fn new(title: impl Into<String>) -> Self {
+    #[allow(clippy::needless_pass_by_value)]
-        let title = title.into();
+    pub fn new(title: impl ToString) -> Self {
+        let title = title.to_string();
         let area = Area::new(&title);
         let title_label = Label::new(title).text_style(TextStyle::Heading).wrap(false);
         Self {

egui/src/data/output.rs

@@ -31,7 +31,7 @@ pub struct Output {
 impl Output {
     /// Open the given url in a web browser.
     /// If egui is running in a browser, the same tab will be reused.
-    pub fn open_url(&mut self, url: impl Into<String>) {
+    pub fn open_url(&mut self, url: impl ToString) {
         self.open_url = Some(OpenUrl::same_tab(url))
     }
 
@@ -59,16 +59,18 @@ pub struct OpenUrl {
 }
 
 impl OpenUrl {
-    pub fn same_tab(url: impl Into<String>) -> Self {
+    #[allow(clippy::needless_pass_by_value)]
+    pub fn same_tab(url: impl ToString) -> Self {
         Self {
-            url: url.into(),
+            url: url.to_string(),
             new_tab: false,
         }
     }
 
-    pub fn new_tab(url: impl Into<String>) -> Self {
+    #[allow(clippy::needless_pass_by_value)]
+    pub fn new_tab(url: impl ToString) -> Self {
         Self {
-            url: url.into(),
+            url: url.to_string(),
             new_tab: true,
         }
     }
@@ -279,17 +281,19 @@ impl WidgetInfo {
         }
     }
 
-    pub fn labeled(typ: WidgetType, label: impl Into<String>) -> Self {
+    #[allow(clippy::needless_pass_by_value)]
+    pub fn labeled(typ: WidgetType, label: impl ToString) -> Self {
         Self {
-            label: Some(label.into()),
+            label: Some(label.to_string()),
             ..Self::new(typ)
         }
     }
 
     /// checkboxes, radio-buttons etc
-    pub fn selected(typ: WidgetType, selected: bool, label: impl Into<String>) -> Self {
+    #[allow(clippy::needless_pass_by_value)]
+    pub fn selected(typ: WidgetType, selected: bool, label: impl ToString) -> Self {
         Self {
-            label: Some(label.into()),
+            label: Some(label.to_string()),
             selected: Some(selected),
             ..Self::new(typ)
         }
@@ -302,8 +306,9 @@ impl WidgetInfo {
         }
     }
 
-    pub fn slider(value: f64, label: impl Into<String>) -> Self {
+    #[allow(clippy::needless_pass_by_value)]
-        let label = label.into();
+    pub fn slider(value: f64, label: impl ToString) -> Self {
+        let label = label.to_string();
         Self {
             label: if label.is_empty() { None } else { Some(label) },
             value: Some(value),
@@ -311,9 +316,10 @@ impl WidgetInfo {
         }
     }
 
-    pub fn text_edit(edit_text: impl Into<String>) -> Self {
+    #[allow(clippy::needless_pass_by_value)]
+    pub fn text_edit(edit_text: impl ToString) -> Self {
         Self {
-            edit_text: Some(edit_text.into()),
+            edit_text: Some(edit_text.to_string()),
             ..Self::new(WidgetType::TextEdit)
         }
     }

egui/src/menu.rs

@@ -60,16 +60,13 @@ pub fn bar<R>(ui: &mut Ui, add_contents: impl FnOnce(&mut Ui) -> R) -> InnerResp
 }
 
 /// Construct a top level menu in a menu bar. This would be e.g. "File", "Edit" etc.
-pub fn menu(ui: &mut Ui, title: impl Into<String>, add_contents: impl FnOnce(&mut Ui)) {
+pub fn menu(ui: &mut Ui, title: impl ToString, add_contents: impl FnOnce(&mut Ui)) {
     menu_impl(ui, title, Box::new(add_contents))
 }
 
-fn menu_impl<'c>(
+#[allow(clippy::needless_pass_by_value)]
-    ui: &mut Ui,
+fn menu_impl<'c>(ui: &mut Ui, title: impl ToString, add_contents: Box<dyn FnOnce(&mut Ui) + 'c>) {
-    title: impl Into<String>,
+    let title = title.to_string();
-    add_contents: Box<dyn FnOnce(&mut Ui) + 'c>,
-) {
-    let title = title.into();
     let bar_id = ui.id();
     let menu_id = bar_id.with(&title);
 

egui/src/painter.rs

@@ -173,10 +173,17 @@ impl Painter {
 
 /// ## Debug painting
 impl Painter {
-    pub fn debug_rect(&mut self, rect: Rect, color: Color32, text: impl Into<String>) {
+    #[allow(clippy::needless_pass_by_value)]
+    pub fn debug_rect(&mut self, rect: Rect, color: Color32, text: impl ToString) {
         self.rect_stroke(rect, 0.0, (1.0, color));
         let text_style = TextStyle::Monospace;
-        self.text(rect.min, Align2::LEFT_TOP, text.into(), text_style, color);
+        self.text(
+            rect.min,
+            Align2::LEFT_TOP,
+            text.to_string(),
+            text_style,
+            color,
+        );
     }
 
     pub fn error(&self, pos: Pos2, text: impl std::fmt::Display) -> Rect {
@@ -293,17 +300,18 @@ impl Painter {
     /// To center the text at the given position, use `anchor: (Center, Center)`.
     ///
     /// Returns where the text ended up.
+    #[allow(clippy::needless_pass_by_value)]
     pub fn text(
         &self,
         pos: Pos2,
         anchor: Align2,
-        text: impl Into<String>,
+        text: impl ToString,
         text_style: TextStyle,
         text_color: Color32,
     ) -> Rect {
         let galley = self
             .fonts()
-            .layout_multiline(text_style, text.into(), f32::INFINITY);
+            .layout_multiline(text_style, text.to_string(), f32::INFINITY);
         let rect = anchor.anchor_rect(Rect::from_min_size(pos, galley.size));
         self.galley(rect.min, galley, text_color);
         rect

egui/src/response.rs

@@ -356,21 +356,21 @@ impl Response {
     ///
     /// The text will not be visible if the widget is not enabled.
     /// If you call this multiple times the tooltips will stack underneath the previous ones.
-    pub fn on_hover_text(self, text: impl Into<String>) -> Self {
+    pub fn on_hover_text(self, text: impl ToString) -> Self {
         self.on_hover_ui(|ui| {
             ui.add(crate::widgets::Label::new(text));
         })
     }
 
     /// Show this text when hovering if the widget is disabled.
-    pub fn on_disabled_hover_text(self, text: impl Into<String>) -> Self {
+    pub fn on_disabled_hover_text(self, text: impl ToString) -> Self {
         self.on_disabled_hover_ui(|ui| {
             ui.add(crate::widgets::Label::new(text));
         })
     }
 
     #[deprecated = "Deprecated 2020-10-01: use `on_hover_text` instead."]
-    pub fn tooltip_text(self, text: impl Into<String>) -> Self {
+    pub fn tooltip_text(self, text: impl ToString) -> Self {
         self.on_hover_text(text)
     }
 

egui/src/ui.rs

@@ -899,7 +899,7 @@ impl Ui {
     /// Shortcut for `add(Hyperlink::new(url))`
     ///
     /// See also [`Hyperlink`].
-    pub fn hyperlink(&mut self, url: impl Into<String>) -> Response {
+    pub fn hyperlink(&mut self, url: impl ToString) -> Response {
         Hyperlink::new(url).ui(self)
     }
 
@@ -911,7 +911,7 @@ impl Ui {
     /// ```
     ///
     /// See also [`Hyperlink`].
-    pub fn hyperlink_to(&mut self, label: impl Into<String>, url: impl Into<String>) -> Response {
+    pub fn hyperlink_to(&mut self, label: impl ToString, url: impl ToString) -> Response {
         Hyperlink::new(url).text(label).ui(self)
     }
 
@@ -941,7 +941,7 @@ impl Ui {
     /// See also [`Button`].
     #[must_use = "You should check if the user clicked this with `if ui.button(…).clicked() { … } "]
     #[inline(always)]
-    pub fn button(&mut self, text: impl Into<String>) -> Response {
+    pub fn button(&mut self, text: impl ToString) -> Response {
         Button::new(text).ui(self)
     }
 
@@ -951,19 +951,19 @@ impl Ui {
     ///
     /// Shortcut for `add(Button::new(text).small())`
     #[must_use = "You should check if the user clicked this with `if ui.small_button(…).clicked() { … } "]
-    pub fn small_button(&mut self, text: impl Into<String>) -> Response {
+    pub fn small_button(&mut self, text: impl ToString) -> Response {
         Button::new(text).small().ui(self)
     }
 
     /// Show a checkbox.
-    pub fn checkbox(&mut self, checked: &mut bool, text: impl Into<String>) -> Response {
+    pub fn checkbox(&mut self, checked: &mut bool, text: impl ToString) -> Response {
         Checkbox::new(checked, text).ui(self)
     }
 
     /// Show a [`RadioButton`].
     /// Often you want to use [`Self::radio_value`] instead.
     #[must_use = "You should check if the user clicked this with `if ui.radio(…).clicked() { … } "]
-    pub fn radio(&mut self, selected: bool, text: impl Into<String>) -> Response {
+    pub fn radio(&mut self, selected: bool, text: impl ToString) -> Response {
         RadioButton::new(selected, text).ui(self)
     }
 
@@ -988,7 +988,7 @@ impl Ui {
         &mut self,
         current_value: &mut Value,
         selected_value: Value,
-        text: impl Into<String>,
+        text: impl ToString,
     ) -> Response {
         let mut response = self.radio(*current_value == selected_value, text);
         if response.clicked() {
@@ -1002,7 +1002,7 @@ impl Ui {
     ///
     /// See also [`SelectableLabel`].
     #[must_use = "You should check if the user clicked this with `if ui.selectable_label(…).clicked() { … } "]
-    pub fn selectable_label(&mut self, checked: bool, text: impl Into<String>) -> Response {
+    pub fn selectable_label(&mut self, checked: bool, text: impl ToString) -> Response {
         SelectableLabel::new(checked, text).ui(self)
     }
 
@@ -1016,7 +1016,7 @@ impl Ui {
         &mut self,
         current_value: &mut Value,
         selected_value: Value,
-        text: impl Into<String>,
+        text: impl ToString,
     ) -> Response {
         let mut response = self.selectable_label(*current_value == selected_value, text);
         if response.clicked() {
@@ -1212,7 +1212,7 @@ impl Ui {
     /// A [`CollapsingHeader`] that starts out collapsed.
     pub fn collapsing<R>(
         &mut self,
-        heading: impl Into<String>,
+        heading: impl ToString,
         add_contents: impl FnOnce(&mut Ui) -> R,
     ) -> CollapsingResponse<R> {
         CollapsingHeader::new(heading).show(self, add_contents)

egui/src/widgets/button.rs

@@ -26,9 +26,10 @@ pub struct Button {
 }
 
 impl Button {
-    pub fn new(text: impl Into<String>) -> Self {
+    #[allow(clippy::needless_pass_by_value)]
+    pub fn new(text: impl ToString) -> Self {
         Self {
-            text: text.into(),
+            text: text.to_string(),
             text_color: None,
             text_style: TextStyle::Button,
             fill: Default::default(),
@@ -211,10 +212,11 @@ pub struct Checkbox<'a> {
 }
 
 impl<'a> Checkbox<'a> {
-    pub fn new(checked: &'a mut bool, text: impl Into<String>) -> Self {
+    #[allow(clippy::needless_pass_by_value)]
+    pub fn new(checked: &'a mut bool, text: impl ToString) -> Self {
         Checkbox {
             checked,
-            text: text.into(),
+            text: text.to_string(),
             text_color: None,
         }
     }
@@ -321,10 +323,11 @@ pub struct RadioButton {
 }
 
 impl RadioButton {
-    pub fn new(checked: bool, text: impl Into<String>) -> Self {
+    #[allow(clippy::needless_pass_by_value)]
+    pub fn new(checked: bool, text: impl ToString) -> Self {
         Self {
             checked,
-            text: text.into(),
+            text: text.to_string(),
             text_color: None,
         }
     }

egui/src/widgets/hyperlink.rs

@@ -16,24 +16,27 @@ pub struct Hyperlink {
 }
 
 impl Hyperlink {
-    pub fn new(url: impl Into<String>) -> Self {
+    #[allow(clippy::needless_pass_by_value)]
-        let url = url.into();
+    pub fn new(url: impl ToString) -> Self {
+        let url = url.to_string();
         Self {
             url: url.clone(),
             label: Label::new(url),
         }
     }
 
-    pub fn from_label_and_url(label: impl Into<Label>, url: impl Into<String>) -> Self {
+    #[allow(clippy::needless_pass_by_value)]
+    pub fn from_label_and_url(label: impl Into<Label>, url: impl ToString) -> Self {
         Self {
-            url: url.into(),
+            url: url.to_string(),
             label: label.into(),
         }
     }
 
     /// Show some other text than the url
-    pub fn text(mut self, text: impl Into<String>) -> Self {
+    #[allow(clippy::needless_pass_by_value)]
-        self.label.text = text.into();
+    pub fn text(mut self, text: impl ToString) -> Self {
+        self.label.text = text.to_string();
         self
     }
 

egui/src/widgets/label.rs

@@ -29,9 +29,10 @@ pub struct Label {
 }
 
 impl Label {
-    pub fn new(text: impl Into<String>) -> Self {
+    #[allow(clippy::needless_pass_by_value)]
+    pub fn new(text: impl ToString) -> Self {
         Self {
-            text: text.into(),
+            text: text.to_string(),
             wrap: None,
             text_style: None,
             background_color: Color32::TRANSPARENT,

egui/src/widgets/selected_label.rs

@@ -28,10 +28,11 @@ pub struct SelectableLabel {
 }
 
 impl SelectableLabel {
-    pub fn new(selected: bool, text: impl Into<String>) -> Self {
+    #[allow(clippy::needless_pass_by_value)]
+    pub fn new(selected: bool, text: impl ToString) -> Self {
         Self {
             selected,
-            text: text.into(),
+            text: text.to_string(),
         }
     }
 }

egui/src/widgets/slider.rs

@@ -174,8 +174,8 @@ impl<'a> Slider<'a> {
     }
 
     /// Show a text next to the slider (e.g. explaining what the slider controls).
-    pub fn text(mut self, text: impl Into<String>) -> Self {
+    pub fn text(mut self, text: impl ToString) -> Self {
-        self.text = text.into();
+        self.text = text.to_string();
         self
     }
 

egui/src/widgets/text_edit.rs

@@ -204,8 +204,9 @@ impl<'t> TextEdit<'t> {
     }
 
     /// Show a faint hint text when the text field is empty.
-    pub fn hint_text(mut self, hint_text: impl Into<String>) -> Self {
+    #[allow(clippy::needless_pass_by_value)]
-        self.hint_text = hint_text.into();
+    pub fn hint_text(mut self, hint_text: impl ToString) -> Self {
+        self.hint_text = hint_text.to_string();
         self
     }
 

epaint/src/shape.rs

@@ -124,15 +124,16 @@ impl Shape {
         }
     }
 
+    #[allow(clippy::needless_pass_by_value)]
     pub fn text(
         fonts: &Fonts,
         pos: Pos2,
         anchor: Align2,
-        text: impl Into<String>,
+        text: impl ToString,
         text_style: TextStyle,
         color: Color32,
     ) -> Self {
-        let galley = fonts.layout_multiline(text_style, text.into(), f32::INFINITY);
+        let galley = fonts.layout_multiline(text_style, text.to_string(), f32::INFINITY);
         let rect = anchor.anchor_rect(Rect::from_min_size(pos, galley.size));
         Self::Text {
             pos: rect.min,

epi/src/lib.rs

@@ -340,20 +340,20 @@ pub mod http {
 
     impl Request {
         /// Create a `GET` requests with the given url.
-        pub fn get(url: impl Into<String>) -> Self {
+        pub fn get(url: impl ToString) -> Self {
             Self {
                 method: "GET".to_owned(),
-                url: url.into(),
+                url: url.to_string(),
                 body: "".to_string(),
             }
         }
 
         /// Create a `POST` requests with the give url and body.
-        pub fn post(url: impl Into<String>, body: impl Into<String>) -> Self {
+        pub fn post(url: impl ToString, body: impl ToString) -> Self {
             Self {
                 method: "POST".to_owned(),
-                url: url.into(),
+                url: url.to_string(),
-                body: body.into(),
+                body: body.to_string(),
             }
         }
     }