1 files changed, 183 insertions, 0 deletions
diff --git a/src/tools/rust-analyzer/crates/ide-assists/src/handlers/number_representation.rs b/src/tools/rust-analyzer/crates/ide-assists/src/handlers/number_representation.rs
new file mode 100644
index 000000000..424db7437
--- /dev/null
+++ b/src/tools/rust-analyzer/crates/ide-assists/src/handlers/number_representation.rs
@@ -0,0 +1,183 @@
+use syntax::{ast, ast::Radix, AstToken};
+
+use crate::{AssistContext, AssistId, AssistKind, Assists, GroupLabel};
+
+const MIN_NUMBER_OF_DIGITS_TO_FORMAT: usize = 5;
+
+// Assist: reformat_number_literal
+//
+// Adds or removes separators from integer literal.
+//
+// ```
+// const _: i32 = 1012345$0;
+// ```
+// ->
+// ```
+// const _: i32 = 1_012_345;
+// ```
+pub(crate) fn reformat_number_literal(acc: &mut Assists, ctx: &AssistContext<'_>) -> Option<()> {
+    let literal = ctx.find_node_at_offset::<ast::Literal>()?;
+    let literal = match literal.kind() {
+        ast::LiteralKind::IntNumber(it) => it,
+        _ => return None,
+    };
+
+    let text = literal.text();
+    if text.contains('_') {
+        return remove_separators(acc, literal);
+    }
+
+    let (prefix, value, suffix) = literal.split_into_parts();
+    if value.len() < MIN_NUMBER_OF_DIGITS_TO_FORMAT {
+        return None;
+    }
+
+    let radix = literal.radix();
+    let mut converted = prefix.to_string();
+    converted.push_str(&add_group_separators(value, group_size(radix)));
+    converted.push_str(suffix);
+
+    let group_id = GroupLabel("Reformat number literal".into());
+    let label = format!("Convert {} to {}", literal, converted);
+    let range = literal.syntax().text_range();
+    acc.add_group(
+        &group_id,
+        AssistId("reformat_number_literal", AssistKind::RefactorInline),
+        label,
+        range,
+        |builder| builder.replace(range, converted),
+    )
+}
+
+fn remove_separators(acc: &mut Assists, literal: ast::IntNumber) -> Option<()> {
+    let group_id = GroupLabel("Reformat number literal".into());
+    let range = literal.syntax().text_range();
+    acc.add_group(
+        &group_id,
+        AssistId("reformat_number_literal", AssistKind::RefactorInline),
+        "Remove digit separators",
+        range,
+        |builder| builder.replace(range, literal.text().replace('_', "")),
+    )
+}
+
+const fn group_size(r: Radix) -> usize {
+    match r {
+        Radix::Binary => 4,
+        Radix::Octal => 3,
+        Radix::Decimal => 3,
+        Radix::Hexadecimal => 4,
+    }
+}
+
+fn add_group_separators(s: &str, group_size: usize) -> String {
+    let mut chars = Vec::new();
+    for (i, ch) in s.chars().filter(|&ch| ch != '_').rev().enumerate() {
+        if i > 0 && i % group_size == 0 {
+            chars.push('_');
+        }
+        chars.push(ch);
+    }
+
+    chars.into_iter().rev().collect()
+}
+
+#[cfg(test)]
+mod tests {
+    use crate::tests::{check_assist_by_label, check_assist_not_applicable, check_assist_target};
+
+    use super::*;
+
+    #[test]
+    fn group_separators() {
+        let cases = vec![
+            ("", 4, ""),
+            ("1", 4, "1"),
+            ("12", 4, "12"),
+            ("123", 4, "123"),
+            ("1234", 4, "1234"),
+            ("12345", 4, "1_2345"),
+            ("123456", 4, "12_3456"),
+            ("1234567", 4, "123_4567"),
+            ("12345678", 4, "1234_5678"),
+            ("123456789", 4, "1_2345_6789"),
+            ("1234567890", 4, "12_3456_7890"),
+            ("1_2_3_4_5_6_7_8_9_0_", 4, "12_3456_7890"),
+            ("1234567890", 3, "1_234_567_890"),
+            ("1234567890", 2, "12_34_56_78_90"),
+            ("1234567890", 1, "1_2_3_4_5_6_7_8_9_0"),
+        ];
+
+        for case in cases {
+            let (input, group_size, expected) = case;
+            assert_eq!(add_group_separators(input, group_size), expected)
+        }
+    }
+
+    #[test]
+    fn good_targets() {
+        let cases = vec![
+            ("const _: i32 = 0b11111$0", "0b11111"),
+            ("const _: i32 = 0o77777$0;", "0o77777"),
+            ("const _: i32 = 10000$0;", "10000"),
+            ("const _: i32 = 0xFFFFF$0;", "0xFFFFF"),
+            ("const _: i32 = 10000i32$0;", "10000i32"),
+            ("const _: i32 = 0b_10_0i32$0;", "0b_10_0i32"),
+        ];
+
+        for case in cases {
+            check_assist_target(reformat_number_literal, case.0, case.1);
+        }
+    }
+
+    #[test]
+    fn bad_targets() {
+        let cases = vec![
+            "const _: i32 = 0b111$0",
+            "const _: i32 = 0b1111$0",
+            "const _: i32 = 0o77$0;",
+            "const _: i32 = 0o777$0;",
+            "const _: i32 = 10$0;",
+            "const _: i32 = 999$0;",
+            "const _: i32 = 0xFF$0;",
+            "const _: i32 = 0xFFFF$0;",
+        ];
+
+        for case in cases {
+            check_assist_not_applicable(reformat_number_literal, case);
+        }
+    }
+
+    #[test]
+    fn labels() {
+        let cases = vec![
+            ("const _: i32 = 10000$0", "const _: i32 = 10_000", "Convert 10000 to 10_000"),
+            (
+                "const _: i32 = 0xFF0000$0;",
+                "const _: i32 = 0xFF_0000;",
+                "Convert 0xFF0000 to 0xFF_0000",
+            ),
+            (
+                "const _: i32 = 0b11111111$0;",
+                "const _: i32 = 0b1111_1111;",
+                "Convert 0b11111111 to 0b1111_1111",
+            ),
+            (
+                "const _: i32 = 0o377211$0;",
+                "const _: i32 = 0o377_211;",
+                "Convert 0o377211 to 0o377_211",
+            ),
+            (
+                "const _: i32 = 10000i32$0;",
+                "const _: i32 = 10_000i32;",
+                "Convert 10000i32 to 10_000i32",
+            ),
+            ("const _: i32 = 1_0_0_0_i32$0;", "const _: i32 = 1000i32;", "Remove digit separators"),
+        ];
+
+        for case in cases {
+            let (before, after, label) = case;
+            check_assist_by_label(reformat_number_literal, before, after, label);
+        }
+    }
+}