transpile: mint new CTypeIds when necessary in TypedAstContext::type_for_kind

Author: fw-immunant

c2rust-transpile/src/c_ast/mod.rs

@@ -716,9 +716,26 @@ impl TypedAstContext {
     }
 
     pub fn type_for_kind(&self, kind: &CTypeKind) -> Option<CTypeId> {
-        self.c_types
+        let ro = self.c_types.clone().into_read_only();
+        if let Some(ty) = ro
             .iter()
             .find_map(|(id, k)| if kind == &k.kind { Some(*id) } else { None })
+        {
+            return Some(ty);
+        }
+        let max_type_id = ro
+            .keys()
+            .max_by_key(|id| id.0)
+            .expect("expected non-empty AstContext::c_types");
+        let new_id = CTypeId(max_type_id.0 + 1);
+        self.c_types.insert(
+            new_id,
+            Located {
+                loc: None,
+                kind: kind.clone(),
+            },
+        );
+        Some(new_id)
     }
 
     pub fn resolve_type_id(&self, typ: CTypeId) -> CTypeId {