From efe7df7f45f585278feb41a13ce73d3916d24b4c Mon Sep 17 00:00:00 2001
From: Nick Fitzgerald <fitzgen@gmail.com>
Date: Mon, 11 Oct 2021 11:32:49 -0700
Subject: [PATCH] Keep track of where primitives are defined for better error
 messages

---
 cranelift/isle/isle/src/codegen.rs |  4 ++--
 cranelift/isle/isle/src/sema.rs    | 24 +++++++++++++++++++-----
 2 files changed, 21 insertions(+), 7 deletions(-)

diff --git a/cranelift/isle/isle/src/codegen.rs b/cranelift/isle/isle/src/codegen.rs
index 32e291a4dc..ca983d922a 100644
--- a/cranelift/isle/isle/src/codegen.rs
+++ b/cranelift/isle/isle/src/codegen.rs
@@ -173,7 +173,7 @@ impl<'a> Codegen<'a> {
 
     fn type_name(&self, typeid: TypeId, by_ref: bool) -> String {
         match &self.typeenv.types[typeid.index()] {
-            &Type::Primitive(_, sym) => self.typeenv.syms[sym.index()].clone(),
+            &Type::Primitive(_, sym, _) => self.typeenv.syms[sym.index()].clone(),
             &Type::Enum { name, .. } => {
                 let r = if by_ref { "&" } else { "" };
                 format!("{}{}", r, self.typeenv.syms[name.index()])
@@ -229,7 +229,7 @@ impl<'a> Codegen<'a> {
 
     fn const_int(&self, val: i64, ty: TypeId) -> String {
         let is_bool = match &self.typeenv.types[ty.index()] {
-            &Type::Primitive(_, name) => &self.typeenv.syms[name.index()] == "bool",
+            &Type::Primitive(_, name, _) => &self.typeenv.syms[name.index()] == "bool",
             _ => unreachable!(),
         };
         if is_bool {
diff --git a/cranelift/isle/isle/src/sema.rs b/cranelift/isle/isle/src/sema.rs
index ae87981b65..9b6e8dfde7 100644
--- a/cranelift/isle/isle/src/sema.rs
+++ b/cranelift/isle/isle/src/sema.rs
@@ -94,7 +94,7 @@ pub enum Type {
     ///
     /// These are always defined externally, and we allow literals of these
     /// types to pass through from ISLE source code to the emitted Rust code.
-    Primitive(TypeId, Sym),
+    Primitive(TypeId, Sym, Pos),
 
     /// A sum type.
     ///
@@ -120,7 +120,14 @@ impl Type {
     /// Get the name of this `Type`.
     pub fn name<'a>(&self, tyenv: &'a TypeEnv) -> &'a str {
         match self {
-            Self::Primitive(_, name) | Self::Enum { name, .. } => &tyenv.syms[name.index()],
+            Self::Primitive(_, name, _) | Self::Enum { name, .. } => &tyenv.syms[name.index()],
+        }
+    }
+
+    /// Get the position where this type was defined.
+    pub fn pos(&self) -> Pos {
+        match self {
+            Self::Primitive(_, _, pos) | Self::Enum { pos, .. } => *pos,
         }
     }
 
@@ -551,13 +558,20 @@ impl TypeEnv {
                 &ast::Def::Type(ref td) => {
                     let tid = TypeId(tyenv.type_map.len());
                     let name = tyenv.intern_mut(&td.name);
-                    if tyenv.type_map.contains_key(&name) {
+
+                    if let Some(existing) = tyenv.type_map.get(&name).copied() {
                         tyenv.report_error(
                             td.pos,
-                            format!("Type name defined more than once: '{}'", td.name.0),
+                            format!("Type with name '{}' defined more than once", td.name.0),
+                        );
+                        let pos = unwrap_or_continue!(tyenv.types.get(existing.index())).pos();
+                        tyenv.report_error(
+                            pos,
+                            format!("Type with name '{}' already defined here", td.name.0),
                         );
                         continue;
                     }
+
                     tyenv.type_map.insert(name, tid);
                 }
                 _ => {}
@@ -619,7 +633,7 @@ impl TypeEnv {
         let name = self.intern(&ty.name).unwrap();
         match &ty.ty {
             &ast::TypeValue::Primitive(ref id, ..) => {
-                Some(Type::Primitive(tid, self.intern_mut(id)))
+                Some(Type::Primitive(tid, self.intern_mut(id), ty.pos))
             }
             &ast::TypeValue::Enum(ref ty_variants, ..) => {
                 let mut variants = vec![];