core: Minor StringContext API changes

- Rename `get_char` to `make_char`, and `get_ascii_char` to `ascii_char`:
  this makes clearer that only `make_char` may allocate.
- Take a `u8` instead of a `char` in `ascii_char`.
- Take a `Range<usize>` instead of two `usize` args in `substring`.

core/src/avm2/globals/avmplus.rs

@@ -541,7 +541,7 @@ fn display_name<'gc>(
     if let Some(name) = name {
         name.to_qualified_name_or_star(context)
     } else {
-        context.get_ascii_char('*')
+        context.ascii_char(b'*')
     }
 }
 

core/src/avm2/globals/string.rs

@@ -130,7 +130,7 @@ fn char_at<'gc>(
 
         let index = if !n.is_nan() { n as usize } else { 0 };
         let ret = if let Some(c) = s.get(index) {
-            activation.strings().get_char(c)
+            activation.strings().make_char(c)
         } else {
             activation.strings().empty()
         };
@@ -449,7 +449,7 @@ fn slice<'gc>(
     if start_index < end_index {
         Ok(activation
             .strings()
-            .substring(this, start_index, end_index)
+            .substring(this, start_index..end_index)
             .into())
     } else {
         Ok("".into())
@@ -486,7 +486,7 @@ fn split<'gc>(
         // Special case this to match Flash's behavior.
         this.iter()
             .take(limit)
-            .map(|c| Value::from(activation.strings().get_char(c)))
+            .map(|c| Value::from(activation.strings().make_char(c)))
             .collect()
     } else {
         this.split(&delimiter)
@@ -551,7 +551,7 @@ fn substr<'gc>(
 
     Ok(activation
         .strings()
-        .substring(this, start_index, end_index)
+        .substring(this, start_index..end_index)
         .into())
 }
 
@@ -588,7 +588,7 @@ fn substring<'gc>(
 
     Ok(activation
         .strings()
-        .substring(this, start_index, end_index)
+        .substring(this, start_index..end_index)
         .into())
 }
 

core/src/avm2/multiname.rs

@@ -477,7 +477,7 @@ impl<'gc> Multiname<'gc> {
     /// This is used by `describeType`
     pub fn to_qualified_name_or_star(&self, context: &mut StringContext<'gc>) -> AvmString<'gc> {
         if self.is_any_name() {
-            context.get_ascii_char('*')
+            context.ascii_char(b'*')
         } else {
             self.to_qualified_name(context.gc_context)
         }

core/src/avm2/property.rs

@@ -116,7 +116,7 @@ impl<'gc> PropertyClass<'gc> {
         match self {
             PropertyClass::Class(class) => class.name().to_qualified_name(context.gc_context),
             PropertyClass::Name(name, _) => name.to_qualified_name_or_star(context),
-            PropertyClass::Any => context.get_ascii_char('*'),
+            PropertyClass::Any => context.ascii_char(b'*'),
         }
     }
 }

core/src/avm2/value.rs

@@ -839,7 +839,7 @@ impl<'gc> Value<'gc> {
             }
             Value::Integer(i) => {
                 if *i >= 0 && *i < 10 {
-                    activation.strings().get_char('0' as u16 + *i as u16)
+                    activation.strings().make_char('0' as u16 + *i as u16)
                 } else {
                     AvmString::new_utf8(activation.context.gc_context, i.to_string())
                 }

core/src/string/context.rs

@@ -1,4 +1,4 @@
-use std::borrow::Cow;
+use std::{borrow::Cow, ops::Range};
 
 use gc_arena::{Gc, Mutation};
 
@@ -76,28 +76,23 @@ impl<'gc> StringContext<'gc> {
     }
 
     #[must_use]
-    pub fn get_char(&self, c: u16) -> AvmString<'gc> {
+    pub fn make_char(&self, c: u16) -> AvmString<'gc> {
         if let Some(s) = self.interner.chars.get(c as usize) {
             (*s).into()
         } else {
             AvmString::new(self.gc(), WString::from_unit(c))
         }
     }
 
-    // Like get_char, but panics if the passed char is not ASCII.
+    /// Like `make_char`, but panics if the passed char is not ASCII.
     #[must_use]
-    pub fn get_ascii_char(&self, c: char) -> AvmString<'gc> {
+    pub fn ascii_char(&self, c: u8) -> AvmString<'gc> {
         self.interner.chars[c as usize].into()
     }
 
     #[must_use]
-    pub fn substring(
-        &self,
-        s: AvmString<'gc>,
-        start_index: usize,
-        end_index: usize,
-    ) -> AvmString<'gc> {
+    pub fn substring(&self, s: AvmString<'gc>, range: Range<usize>) -> AvmString<'gc> {
         self.interner
-            .substring(self.gc(), s, start_index, end_index)
+            .substring(self.gc(), s, range.start, range.end)
     }
 }