tamer: relroot String->SymbolId

This was [one of] the last remaining Strings; SymbolId should be used across
the board.

tamer/src/ir/legacyir.rs

@@ -41,7 +41,7 @@ pub struct PackageAttrs {
     pub name: Option<SymbolId>,
 
     /// Relative path from package to project root.
-    pub relroot: Option<String>,
+    pub relroot: Option<SymbolId>,
 
     /// Whether this package is a program.
     ///

tamer/src/ld/poc.rs

@@ -213,7 +213,7 @@ fn output_xmle<'a>(
     depgraph: &'a LinkerAsg,
     sorted: &mut Sections<'a, IdentObject>,
     name: SymbolId,
-    relroot: String,
+    relroot: SymbolId,
     output: &str,
 ) -> Result<(), Box<dyn Error>> {
     if !sorted.map.is_empty() {
@@ -237,8 +237,7 @@ fn output_xmle<'a>(
     let file = fs::File::create(output)?;
     let mut buf = BufWriter::new(file);
 
-    lower_iter(&sorted, name, relroot.intern())
-        .write(&mut buf, Default::default())?;
+    lower_iter(&sorted, name, relroot).write(&mut buf, Default::default())?;
 
     buf.flush()?;
 

tamer/src/obj/xmlo/asg_builder.rs

@@ -132,7 +132,7 @@ where
     /// Relative path to project root once discovered.
     ///
     /// This will be set by the first package encountered.
-    pub relroot: Option<String>,
+    pub relroot: Option<SymbolId>,
 }
 
 impl<S, Ix> AsgBuilderState<S, Ix>
@@ -369,11 +369,11 @@ mod test {
         let mut sut = Sut::new();
 
         let name = "name".intern();
-        let relroot = "some/path".to_string();
+        let relroot = "some/path".into();
 
         let evs = vec![Ok(XmloEvent::Package(PackageAttrs {
             name: Some(name),
-            relroot: Some(relroot.clone()),
+            relroot: Some(relroot),
             ..Default::default()
         }))];
 

tamer/src/obj/xmlo/reader/mod.rs

@@ -351,9 +351,9 @@ where
         ele: &'a BytesStart<'a>,
     ) -> XmloResult<PackageAttrs> {
         let mut program = false;
-        let mut elig: Option<SymbolId> = None;
-        let mut name: Option<SymbolId> = None;
-        let mut relroot: Option<String> = None;
+        let mut elig = None;
+        let mut name = None;
+        let mut relroot = None;
 
         for attr in ele.attributes().with_checks(false).filter_map(Result::ok) {
             match attr.key {
@@ -363,9 +363,8 @@ where
                 }
 
                 b"__rootpath" => {
-                    relroot = Some(unsafe {
-                        String::from_utf8_unchecked(attr.value.to_vec())
-                    });
+                    relroot =
+                        Some(unsafe { (&attr.value).intern_utf8_unchecked() });
                 }
 
                 b"program" => {