Make Monotype function identities explicit

Author: rtfeldman

src/eval/test/eval_bughunt_repros.zig

@@ -638,7 +638,6 @@ pub const tests = [_]TestCase{
         \\main = (combine(Baz, Baz, |a, b| a + b) == Baz, combine(Bar(1), Bar(2), |a, b| a + b) == Bar(3))
         ,
         .expected = .{ .inspect_str = "(True, True)" },
-        .known_bug = true,
     },
     .{
         .name = "bughunt B102: recursive Monotype record lowering keeps field span stable",

src/postcheck/monotype/ast.zig

@@ -20,6 +20,10 @@ pub const ExprId = enum(u32) { _ };
 pub const PatId = enum(u32) { _ };
 /// Identifier for a definition in Monotype IR.
 pub const DefId = enum(u32) { _ };
+/// Identifier for a nested definition in Monotype IR.
+pub const NestedDefId = enum(u32) { _ };
+/// Identifier for a function specialization in Monotype IR.
+pub const FnId = enum(u32) { _ };
 /// Identifier for a local binding in Monotype IR.
 pub const LocalId = enum(u32) { _ };
 /// Identifier assigned by Monotype lifting when this storage is consumed.
@@ -82,6 +86,11 @@ pub const FnTemplate = struct {
     mono_fn_ty: Type.TypeId,
 };
 
+/// Monotype function-specialization metadata.
+pub const Fn = struct {
+    source: FnTemplate,
+};
+
 /// Compare the fields that make two function templates identical for Monotype.
 pub fn fnTemplateIdentityEql(lhs: FnTemplate, rhs: FnTemplate) bool {
     return std.meta.eql(lhs.fn_def, rhs.fn_def) and
@@ -181,9 +190,9 @@ pub const TagExpr = struct {
 
 /// Lambda expression before lifting.
 pub const LambdaExpr = struct {
+    fn_id: FnId,
     args: Span(TypedLocal),
     body: ExprId,
-    source: FnTemplate,
 };
 
 /// Call through a function value before lambda solving.
@@ -194,7 +203,7 @@ pub const CallValue = struct {
 
 /// Direct call target before or after Monotype lifting.
 pub const ProcCallee = union(enum) {
-    template: FnTemplate,
+    func: FnId,
     lifted: LiftedFnId,
 };
 
@@ -267,7 +276,7 @@ pub const ExprData = union(enum) {
     },
     lambda: LambdaExpr,
     def_ref: DefId,
-    fn_def: FnTemplate,
+    fn_def: FnId,
     fn_ref: LiftedFnId,
     call_value: CallValue,
     call_proc: CallProc,
@@ -377,6 +386,7 @@ pub const Stmt = union(enum) {
 pub const Def = struct {
     symbol: Common.Symbol,
     fn_def: ?FnTemplate = null,
+    fn_id: ?FnId = null,
     args: Span(TypedLocal),
     body: FnBody,
     ret: Type.TypeId,
@@ -392,6 +402,7 @@ pub const FnBody = union(enum) {
 pub const NestedDef = struct {
     symbol: Common.Symbol,
     fn_def: FnTemplate,
+    fn_id: FnId,
     args: Span(TypedLocal),
     body: ExprId,
     ret: Type.TypeId,
@@ -425,6 +436,7 @@ pub const Program = struct {
     names: names.NameStore,
     next_symbol: u32,
     types: Type.Store,
+    fns: std.ArrayList(Fn),
     defs: std.ArrayList(Def),
     nested_defs: std.ArrayList(NestedDef),
     exprs: std.ArrayList(Expr),
@@ -465,6 +477,7 @@ pub const Program = struct {
             .names = names.NameStore.init(allocator),
             .next_symbol = 0,
             .types = Type.Store.init(allocator),
+            .fns = .empty,
             .defs = .empty,
             .nested_defs = .empty,
             .exprs = .empty,
@@ -521,10 +534,23 @@ pub const Program = struct {
         self.exprs.deinit(self.allocator);
         self.nested_defs.deinit(self.allocator);
         self.defs.deinit(self.allocator);
+        self.fns.deinit(self.allocator);
         self.types.deinit();
         self.names.deinit();
     }
 
+    pub fn addFn(self: *Program, source: FnTemplate) std.mem.Allocator.Error!FnId {
+        const id: FnId = @enumFromInt(@as(u32, @intCast(self.fns.items.len)));
+        try self.fns.append(self.allocator, .{ .source = source });
+        return id;
+    }
+
+    pub fn fnSource(self: *const Program, id: FnId) FnTemplate {
+        const raw = @intFromEnum(id);
+        if (raw >= self.fns.items.len) Common.invariant("Monotype function id referenced a missing specialization");
+        return self.fns.items[raw].source;
+    }
+
     pub fn addExpr(self: *Program, expr: Expr) std.mem.Allocator.Error!ExprId {
         const id: ExprId = @enumFromInt(@as(u32, @intCast(self.exprs.items.len)));
         try self.exprs.append(self.allocator, expr);