From fddff6ee2d87b92015759660e39ce37f4401e833 Mon Sep 17 00:00:00 2001
From: Nick Fitzgerald <fitzgen@gmail.com>
Date: Tue, 5 Oct 2021 16:35:07 -0700
Subject: [PATCH] Fix a panic when checking the call graph for an extractor
 with type errors in its definition

---
 cranelift/isle/isle/src/ast.rs  |  6 +++---
 cranelift/isle/isle/src/sema.rs | 26 +++++++++++++++++++++++---
 2 files changed, 26 insertions(+), 6 deletions(-)

diff --git a/cranelift/isle/isle/src/ast.rs b/cranelift/isle/isle/src/ast.rs
index 5af7eaf6d7..4b2aa84ca0 100644
--- a/cranelift/isle/isle/src/ast.rs
+++ b/cranelift/isle/isle/src/ast.rs
@@ -128,10 +128,10 @@ impl Pattern {
     }
 
     /// Call `f` for each of the terms in this pattern.
-    pub fn terms(&self, f: &mut dyn FnMut(&Ident)) {
+    pub fn terms(&self, f: &mut dyn FnMut(Pos, &Ident)) {
         match self {
-            Pattern::Term { sym, args, .. } => {
-                f(sym);
+            Pattern::Term { sym, args, pos } => {
+                f(*pos, sym);
                 for arg in args {
                     if let TermArgPattern::Pattern(p) = arg {
                         p.terms(f);
diff --git a/cranelift/isle/isle/src/sema.rs b/cranelift/isle/isle/src/sema.rs
index 14062ea3f0..f437a23279 100644
--- a/cranelift/isle/isle/src/sema.rs
+++ b/cranelift/isle/isle/src/sema.rs
@@ -847,17 +847,29 @@ impl TermEnv {
                         return;
                     }
                 };
-                let termdata = &mut self.terms[term.index()];
+
                 let template = ext.template.make_macro_template(&ext.args[..]);
                 log::trace!("extractor def: {:?} becomes template {:?}", def, template);
 
                 let mut callees = HashSet::new();
-                template.terms(&mut |t| {
+                template.terms(&mut |pos, t| {
                     let t = tyenv.intern_mut(t);
                     callees.insert(t);
+
+                    if !self.term_map.contains_key(&t) {
+                        tyenv.report_error(
+                            pos,
+                            format!(
+                                "`{}` extractor definition references unknown term `{}`",
+                                ext.term.0,
+                                tyenv.syms[t.index()]
+                            ),
+                        );
+                    }
                 });
                 extractor_call_graph.insert(sym, callees);
 
+                let termdata = &mut self.terms[term.index()];
                 match &termdata.kind {
                     &TermKind::Declared => {
                         termdata.kind = TermKind::InternalExtractor { template };
@@ -892,7 +904,15 @@ impl TermEnv {
                         }));
                     }
                 } else {
-                    let term = self.term_map[&caller];
+                    let term = match self.term_map.get(&caller) {
+                        Some(t) => t,
+                        None => {
+                            // Some other error must have already been recorded
+                            // if we don't have the caller's term data.
+                            assert!(!tyenv.errors.is_empty());
+                            continue 'outer;
+                        }
+                    };
                     let pos = match &self.terms[term.index()].kind {
                         TermKind::InternalExtractor { template } => template.pos(),
                         _ => unreachable!(),