Merge remote-tracking branch 'origin/trunk' into recursive-tag-segfault

compiler/mono/src/layout.rs

@@ -1,9 +1,10 @@
 use bumpalo::collections::Vec;
 use bumpalo::Bump;
-use roc_collections::all::{MutMap, MutSet};
+use roc_collections::all::{default_hasher, MutMap, MutSet};
 use roc_module::ident::{Lowercase, TagName};
-use roc_module::symbol::Symbol;
+use roc_module::symbol::{Interns, Symbol};
 use roc_types::subs::{Content, FlatType, Subs, Variable};
+use std::collections::HashMap;
 
 pub const MAX_ENUM_SIZE: usize = (std::mem::size_of::<u8>() * 8) as usize;
 
@@ -1298,3 +1299,52 @@ pub fn mode_from_var(var: Variable, subs: &Subs) -> MemoryMode {
         _ => MemoryMode::Refcounted,
     }
 }
+
+#[derive(Debug, Clone, Copy, PartialEq, Eq)]
+pub struct LayoutId(u32);
+
+impl LayoutId {
+    // Returns something like "foo#1" when given a symbol that interns to "foo"
+    // and a LayoutId of 1.
+    pub fn to_symbol_string(self, symbol: Symbol, interns: &Interns) -> String {
+        let ident_string = symbol.ident_string(interns);
+        let module_string = interns.module_ids.get_name(symbol.module_id()).unwrap();
+        format!("{}_{}_{}", module_string, ident_string, self.0)
+    }
+}
+
+struct IdsByLayout<'a> {
+    by_id: MutMap<Layout<'a>, u32>,
+    next_id: u32,
+}
+
+#[derive(Default)]
+pub struct LayoutIds<'a> {
+    by_symbol: MutMap<Symbol, IdsByLayout<'a>>,
+}
+
+impl<'a> LayoutIds<'a> {
+    /// Returns a LayoutId which is unique for the given symbol and layout.
+    /// If given the same symbol and same layout, returns the same LayoutId.
+    pub fn get(&mut self, symbol: Symbol, layout: &Layout<'a>) -> LayoutId {
+        // Note: this function does some weird stuff to satisfy the borrow checker.
+        // There's probably a nicer way to write it that still works.
+        let ids = self.by_symbol.entry(symbol).or_insert_with(|| IdsByLayout {
+            by_id: HashMap::with_capacity_and_hasher(1, default_hasher()),
+            next_id: 1,
+        });
+
+        // Get the id associated with this layout, or default to next_id.
+        let answer = ids.by_id.get(layout).copied().unwrap_or(ids.next_id);
+
+        // If we had to default to next_id, it must not have been found;
+        // store the ID we're going to return and increment next_id.
+        if answer == ids.next_id {
+            ids.by_id.insert(layout.clone(), ids.next_id);
+
+            ids.next_id += 1;
+        }
+
+        LayoutId(answer)
+    }
+}