Avoid demo parameter collisions in function definitions (#717)

* Adding code for detecting collisions in parameter names

* Generation

* Move logic into append_out_param

* Use parameter name instead of terminusArgs

* Generation

* Formatting

* Useless comment

* Formatting

tool/src/demo_gen/mod.rs

@@ -3,7 +3,10 @@
 //! Designed to work in conjunction with the JS backend.
 //!
 //! See docs/demo_gen.md for more.
-use std::{collections::BTreeSet, fmt::Write};
+use std::{
+    collections::{BTreeSet, HashMap},
+    fmt::Write,
+};
 
 use askama::{self, Template};
 use diplomat_core::hir::{BackendAttrSupport, TypeContext};
@@ -201,6 +204,8 @@ pub(crate) fn run<'tcx>(
                         imports: BTreeSet::new(),
                     },
 
+                    out_param_collision: HashMap::new(),
+
                     relative_import_path: import_path.clone(),
                     module_name: module_name.clone(),
                 };

tool/src/demo_gen/terminus.rs

@@ -1,4 +1,4 @@
-use std::collections::BTreeSet;
+use std::collections::{BTreeSet, HashMap};
 
 use diplomat_core::hir::{
     self, DemoInfo, Method, OpaqueDef, StructDef, StructPath, TyPosition, Type, TypeContext,
@@ -54,6 +54,9 @@ pub(super) struct RenderTerminusContext<'ctx, 'tcx> {
     pub errors: &'ctx ErrorStore<'tcx, String>,
     pub terminus_info: TerminusInfo,
 
+    /// To avoid similar parameter names while we're collecting [`OutParam`]s.
+    pub out_param_collision: HashMap<String, i32>,
+
     pub relative_import_path: String,
     pub module_name: String,
 }
@@ -236,8 +239,18 @@ impl<'ctx, 'tcx> RenderTerminusContext<'ctx, 'tcx> {
             }
         };
 
+        let (p, n) = if self.out_param_collision.contains_key(&param_name) {
+            let n = self.out_param_collision.get(&param_name).unwrap();
+
+            (format!("{param_name}_{n}"), n + 1)
+        } else {
+            (param_name.clone(), 1)
+        };
+
+        self.out_param_collision.insert(param_name, n);
+
         let out_param = OutParam {
-            param_name,
+            param_name: p.clone(),
             label,
             type_name: type_name.clone(),
             type_use,
@@ -246,10 +259,7 @@ impl<'ctx, 'tcx> RenderTerminusContext<'ctx, 'tcx> {
 
         self.terminus_info.out_params.push(out_param);
 
-        let param_info = ParamInfo {
-            // Grab arguments without having to name them
-            js: format!("terminusArgs[{}]", self.terminus_info.out_params.len() - 1),
-        };
+        let param_info = ParamInfo { js: p };
 
         node.params.push(param_info);
     }

tool/templates/demo_gen/terminus.js.jinja

@@ -1,9 +1,8 @@
 export function {{function_name}}(
-    {%- if typescript %}{%- for param in out_params -%}
+    {%- for param in out_params -%}
     {{param.param_name}}{% if typescript %}: {{param.type_name}}{% endif %}{% if !loop.last %}, {% endif %}
-    {%- endfor -%}{% endif -%}
+    {%- endfor -%}
 ){% if typescript %};{% else %} {
-    var terminusArgs = arguments;
     return {{node_call_stack|indent(4)}};
 }
 {%- endif %}