Fix literal hovers being confusing and wrong for floats

crates/ide/src/hover/render.rs

@@ -17,11 +17,7 @@ use ide_db::{
 };
 use itertools::Itertools;
 use stdx::format_to;
-use syntax::{
-    algo,
-    ast::{self, RecordPat},
-    match_ast, AstNode, Direction, SyntaxToken, T,
-};
+use syntax::{algo, ast, match_ast, AstNode, AstToken, Direction, SyntaxToken, T};
 
 use crate::{
     doc_links::{remove_links, rewrite_links},
@@ -276,7 +272,7 @@ pub(super) fn keyword(
 pub(super) fn struct_rest_pat(
     sema: &Semantics<'_, RootDatabase>,
     _config: &HoverConfig,
-    pattern: &RecordPat,
+    pattern: &ast::RecordPat,
 ) -> HoverResult {
     let missing_fields = sema.record_pattern_missing_fields(pattern);
 
@@ -526,6 +522,54 @@ pub(super) fn definition(
     markup(docs.map(Into::into), desc, mod_path)
 }
 
+pub(super) fn literal(sema: &Semantics<'_, RootDatabase>, token: SyntaxToken) -> Option<Markup> {
+    let lit = token.parent().and_then(ast::Literal::cast)?;
+    let ty = if let Some(p) = lit.syntax().parent().and_then(ast::Pat::cast) {
+        sema.type_of_pat(&p)?
+    } else {
+        sema.type_of_expr(&ast::Expr::Literal(lit))?
+    }
+    .original;
+
+    let value = match_ast! {
+        match token {
+            ast::String(string) => Ok(string.value()?.to_string()),
+            ast::ByteString(string) => Ok(format_args!("{:?}", string.value()?).to_string()),
+            ast::CString(string) => Ok(std::str::from_utf8(string.value()?.as_ref()).ok()?.to_owned()),
+            ast::Char(char) => Ok(char.value()?.to_string()),
+            ast::Byte(byte) => Ok(format!("0x{:X}", byte.value()?)),
+            ast::FloatNumber(num) => {
+                let (text, _) = num.split_into_parts();
+                let text = text.replace('_', "");
+                if ty.as_builtin().map(|it| it.is_f32()).unwrap_or(false) {
+                    match text.parse::<f32>() {
+                        Ok(num) => Ok(format!("{num} (bits: 0x{:X})", num.to_bits())),
+                        Err(e) => Err(e.to_string()),
+                    }
+                } else {
+                    match text.parse::<f64>() {
+                        Ok(num) => Ok(format!("{num} (bits: 0x{:X})", num.to_bits())),
+                        Err(e) => Err(e.to_string()),
+                    }
+                }
+            },
+            ast::IntNumber(num) => match num.value() {
+                Ok(num) => Ok(format!("{num} (0x{num:X}|0b{num:b})")),
+                Err(e) => Err(e.to_string()),
+            },
+            _ => return None
+        }
+    };
+    let ty = ty.display(sema.db);
+
+    let mut s = format!("```rust\n{ty}\n```\n___\n\n");
+    match value {
+        Ok(value) => format_to!(s, "value of literal: {value}"),
+        Err(error) => format_to!(s, "invalid literal: {error}"),
+    }
+    Some(s.into())
+}
+
 fn render_notable_trait_comment(
     db: &RootDatabase,
     notable_traits: &[(Trait, Vec<(Option<Type>, Name)>)],