Refactor `camel_case` util functions for new `StrIndex`

3 files changed, 103 insertions, 59 deletions

diff --git a/clippy_lints/src/enum_variants.rs b/clippy_lints/src/enum_variants.rs
index 8d6f7d6fdf1..19f1781d0b0 100644
--- a/clippy_lints/src/enum_variants.rs
+++ b/clippy_lints/src/enum_variants.rs
@@ -1,8 +1,8 @@
 //! lint on enum variants that are prefixed or suffixed by the same characters
 
-use clippy_utils::str_utils;
 use clippy_utils::diagnostics::{span_lint, span_lint_and_help};
 use clippy_utils::source::is_present_in_source;
+use clippy_utils::str_utils;
 use rustc_hir::{EnumDef, Item, ItemKind};
 use rustc_lint::{LateContext, LateLintPass};
 use rustc_session::{declare_tool_lint, impl_lint_pass};
@@ -171,14 +171,14 @@ fn check_variant(
         }
     }
     let first = &def.variants[0].ident.name.as_str();
-    let mut pre = &first[..str_utils::until(&*first)];
-    let mut post = &first[str_utils::from(&*first)..];
+    let mut pre = &first[..str_utils::camel_case_until(&*first).byte_index];
+    let mut post = &first[str_utils::camel_case_start(&*first).byte_index..];
     for var in def.variants {
         let name = var.ident.name.as_str();
 
         let pre_match = partial_match(pre, &name);
         pre = &pre[..pre_match];
-        let pre_camel = str_utils::until(pre);
+        let pre_camel = str_utils::camel_case_until(pre).byte_index;
         pre = &pre[..pre_camel];
         while let Some((next, last)) = name[pre.len()..].chars().zip(pre.chars().rev()).next() {
             if next.is_numeric() {
@@ -186,8 +186,8 @@ fn check_variant(
             }
             if next.is_lowercase() {
                 let last = pre.len() - last.len_utf8();
-                let last_camel = str_utils::until(&pre[..last]);
-                pre = &pre[..last_camel];
+                let last_camel = str_utils::camel_case_until(&pre[..last]);
+                pre = &pre[..last_camel.byte_index];
             } else {
                 break;
             }
@@ -196,8 +196,8 @@ fn check_variant(
         let post_match = partial_rmatch(post, &name);
         let post_end = post.len() - post_match;
         post = &post[post_end..];
-        let post_camel = str_utils::from(post);
-        post = &post[post_camel..];
+        let post_camel = str_utils::camel_case_start(post);
+        post = &post[post_camel.byte_index..];
     }
     let (what, value) = match (pre.is_empty(), post.is_empty()) {
         (true, true) => return,
diff --git a/clippy_utils/src/lib.rs b/clippy_utils/src/lib.rs
index 1c5186dba1b..0637ae3e97b 100644
--- a/clippy_utils/src/lib.rs
+++ b/clippy_utils/src/lib.rs
@@ -37,7 +37,6 @@ pub mod sym_helper;
 #[allow(clippy::module_name_repetitions)]
 pub mod ast_utils;
 pub mod attrs;
-pub mod str_utils;
 pub mod comparisons;
 pub mod consts;
 pub mod diagnostics;
@@ -50,6 +49,7 @@ pub mod paths;
 pub mod ptr;
 pub mod qualify_min_const_fn;
 pub mod source;
+pub mod str_utils;
 pub mod sugg;
 pub mod ty;
 pub mod usage;
diff --git a/clippy_utils/src/str_utils.rs b/clippy_utils/src/str_utils.rs
index a6636e39137..f3de1250d5d 100644
--- a/clippy_utils/src/str_utils.rs
+++ b/clippy_utils/src/str_utils.rs
@@ -1,117 +1,161 @@
+/// Dealing with sting indices can be hard, this struct ensures that both the
+/// character and byte index are provided for correct indexing.
+#[derive(Debug, Default, PartialEq, Eq)]
+pub struct StrIndex {
+    pub char_index: usize,
+    pub byte_index: usize,
+}
+
+impl StrIndex {
+    pub fn new(char_index: usize, byte_index: usize) -> Self {
+        Self { char_index, byte_index }
+    }
+}
+
 /// Returns the index of the character after the first camel-case component of `s`.
+///
+/// ```
+/// assert_eq!(camel_case_until("AbcDef"), StrIndex::new(6, 6));
+/// assert_eq!(camel_case_until("ABCD"), StrIndex::new(0, 0));
+/// assert_eq!(camel_case_until("AbcDD"), StrIndex::new(3, 3));
+/// assert_eq!(camel_case_until("Abc\u{f6}\u{f6}DD"), StrIndex::new(5, 7));
+/// ```
 #[must_use]
-pub fn until(s: &str) -> usize {
-    let mut iter = s.char_indices();
-    if let Some((_, first)) = iter.next() {
+pub fn camel_case_until(s: &str) -> StrIndex {
+    let mut iter = s.char_indices().enumerate();
+    if let Some((_char_index, (_, first))) = iter.next() {
         if !first.is_uppercase() {
-            return 0;
+            return StrIndex::new(0, 0);
         }
     } else {
-        return 0;
+        return StrIndex::new(0, 0);
     }
     let mut up = true;
-    let mut last_i = 0;
-    for (i, c) in iter {
+    let mut last_index = StrIndex::new(0, 0);
+    for (char_index, (byte_index, c)) in iter {
         if up {
             if c.is_lowercase() {
                 up = false;
             } else {
-                return last_i;
+                return last_index;
             }
         } else if c.is_uppercase() {
             up = true;
-            last_i = i;
+            last_index.byte_index = byte_index;
+            last_index.char_index = char_index;
         } else if !c.is_lowercase() {
-            return i;
+            return StrIndex::new(char_index, byte_index);
         }
     }
-    if up { last_i } else { s.len() }
+
+    if up {
+        last_index
+    } else {
+        StrIndex::new(s.chars().count(), s.len())
+    }
 }
 
 /// Returns index of the last camel-case component of `s`.
+///
+/// ```
+/// assert_eq!(camel_case_start("AbcDef"), StrIndex::new(0, 0));
+/// assert_eq!(camel_case_start("abcDef"), StrIndex::new(3, 3));
+/// assert_eq!(camel_case_start("ABCD"), StrIndex::new(4, 4));
+/// assert_eq!(camel_case_start("abcd"), StrIndex::new(4, 4));
+/// assert_eq!(camel_case_start("\u{f6}\u{f6}cd"), StrIndex::new(4, 6));
+/// ```
 #[must_use]
-pub fn from(s: &str) -> usize {
-    let mut iter = s.char_indices().rev();
-    if let Some((_, first)) = iter.next() {
+pub fn camel_case_start(s: &str) -> StrIndex {
+    let char_count = s.chars().count();
+    let range = 0..char_count;
+    let mut iter = range.rev().zip(s.char_indices().rev());
+    if let Some((char_index, (_, first))) = iter.next() {
         if !first.is_lowercase() {
-            return s.len();
+            return StrIndex::new(char_index, s.len());
         }
     } else {
-        return s.len();
+        return StrIndex::new(char_count, s.len());
     }
     let mut down = true;
-    let mut last_i = s.len();
-    for (i, c) in iter {
+    let mut last_index = StrIndex::new(char_count, s.len());
+    for (char_index, (byte_index, c)) in iter {
         if down {
             if c.is_uppercase() {
                 down = false;
-                last_i = i;
+                last_index.byte_index = byte_index;
+                last_index.char_index = char_index;
             } else if !c.is_lowercase() {
-                return last_i;
+                return last_index;
             }
         } else if c.is_lowercase() {
             down = true;
         } else if c.is_uppercase() {
-            last_i = i;
+            last_index.byte_index = byte_index;
+            last_index.char_index = char_index;
         } else {
-            return last_i;
+            return last_index;
         }
     }
-    last_i
+    last_index
 }
 
 #[cfg(test)]
 mod test {
-    use super::{from, until};
+    use super::*;
 
     #[test]
-    fn from_full() {
-        assert_eq!(from("AbcDef"), 0);
-        assert_eq!(from("Abc"), 0);
-        assert_eq!(from("ABcd"), 0);
-        assert_eq!(from("ABcdEf"), 0);
-        assert_eq!(from("AabABcd"), 0);
+    fn camel_case_start_full() {
+        assert_eq!(camel_case_start("AbcDef"), StrIndex::new(0, 0));
+        assert_eq!(camel_case_start("Abc"), StrIndex::new(0, 0));
+        assert_eq!(camel_case_start("ABcd"), StrIndex::new(0, 0));
+        assert_eq!(camel_case_start("ABcdEf"), StrIndex::new(0, 0));
+        assert_eq!(camel_case_start("AabABcd"), StrIndex::new(0, 0));
     }
 
     #[test]
-    fn from_partial() {
-        assert_eq!(from("abcDef"), 3);
-        assert_eq!(from("aDbc"), 1);
-        assert_eq!(from("aabABcd"), 3);
+    fn camel_case_start_partial() {
+        assert_eq!(camel_case_start("abcDef"), StrIndex::new(3, 3));
+        assert_eq!(camel_case_start("aDbc"), StrIndex::new(1, 1));
+        assert_eq!(camel_case_start("aabABcd"), StrIndex::new(3, 3));
+        assert_eq!(camel_case_start("\u{f6}\u{f6}AabABcd"), StrIndex::new(2, 4));
     }
 
     #[test]
-    fn from_not() {
-        assert_eq!(from("AbcDef_"), 7);
-        assert_eq!(from("AbcDD"), 5);
+    fn camel_case_start_not() {
+        assert_eq!(camel_case_start("AbcDef_"), StrIndex::new(7, 7));
+        assert_eq!(camel_case_start("AbcDD"), StrIndex::new(5, 5));
+        assert_eq!(camel_case_start("all_small"), StrIndex::new(9, 9));
+        assert_eq!(camel_case_start("\u{f6}_all_small"), StrIndex::new(11, 12));
     }
 
     #[test]
-    fn from_caps() {
-        assert_eq!(from("ABCD"), 4);
+    fn camel_case_start_caps() {
+        assert_eq!(camel_case_start("ABCD"), StrIndex::new(4, 4));
     }
 
     #[test]
-    fn until_full() {
-        assert_eq!(until("AbcDef"), 6);
-        assert_eq!(until("Abc"), 3);
+    fn camel_case_until_full() {
+        assert_eq!(camel_case_until("AbcDef"), StrIndex::new(6, 6));
+        assert_eq!(camel_case_until("Abc"), StrIndex::new(3, 3));
+        assert_eq!(camel_case_until("Abc\u{f6}\u{f6}\u{f6}"), StrIndex::new(6, 9));
     }
 
     #[test]
-    fn until_not() {
-        assert_eq!(until("abcDef"), 0);
-        assert_eq!(until("aDbc"), 0);
+    fn camel_case_until_not() {
+        assert_eq!(camel_case_until("abcDef"), StrIndex::new(0, 0));
+        assert_eq!(camel_case_until("aDbc"), StrIndex::new(0, 0));
     }
 
     #[test]
-    fn until_partial() {
-        assert_eq!(until("AbcDef_"), 6);
-        assert_eq!(until("CallTypeC"), 8);
-        assert_eq!(until("AbcDD"), 3);
+    fn camel_case_until_partial() {
+        assert_eq!(camel_case_until("AbcDef_"), StrIndex::new(6, 6));
+        assert_eq!(camel_case_until("CallTypeC"), StrIndex::new(8, 8));
+        assert_eq!(camel_case_until("AbcDD"), StrIndex::new(3, 3));
+        assert_eq!(camel_case_until("Abc\u{f6}\u{f6}DD"), StrIndex::new(5, 7));
     }
 
     #[test]
     fn until_caps() {
-        assert_eq!(until("ABCD"), 0);
+        assert_eq!(camel_case_until("ABCD"), StrIndex::new(0, 0));
     }
 }