C#: Compilation failure if variant has same name as one of the cases. (#1535)

* If the variant case and variant name have the same c# names, then add an underscore to the case name

* Add test for variant case with same name as variant

* exclude known c++ failure

Author: yowl

crates/csharp/src/function.rs

@@ -1,5 +1,5 @@
 use crate::csharp_ident::ToCSharpIdent;
-use crate::interface::{InterfaceGenerator, ParameterType};
+use crate::interface::{InterfaceGenerator, ParameterType, variant_new_func_name};
 use crate::world_generator::CSharp;
 use heck::ToUpperCamelCase;
 use std::fmt::Write;
@@ -167,6 +167,7 @@ impl<'a, 'b> FunctionBindgen<'a, 'b> {
             .blocks
             .drain(self.blocks.len() - cases.len()..)
             .collect::<Vec<_>>();
+        let variant_name = self.interface_gen.type_name_with_qualifier(ty, false);
         let ty = self.interface_gen.type_name_with_qualifier(ty, true);
         let generics_position = ty.find('<');
         let lifted = self.locals.tmp("lifted");
@@ -198,7 +199,8 @@ impl<'a, 'b> FunctionBindgen<'a, 'b> {
                     String::new()
                 };
 
-                let method = case_name.to_csharp_ident_upper();
+                let method =
+                    variant_new_func_name(&variant_name, &case_name.to_csharp_ident_upper());
 
                 let call = if let Some(position) = generics_position {
                     let (ty, generics) = ty.split_at(position);

crates/csharp/src/interface.rs

@@ -1409,6 +1409,7 @@ impl<'a> CoreInterfaceGenerator<'a> for InterfaceGenerator<'a> {
             .map(|case| {
                 let case_name = case.name.to_csharp_ident();
                 let tag = case.name.to_csharp_ident_upper();
+                let method_name = variant_new_func_name(&name, &tag);
                 let (parameter, argument) = if let Some(ty) = self.non_empty_type(case.ty.as_ref())
                 {
                     (
@@ -1420,7 +1421,7 @@ impl<'a> CoreInterfaceGenerator<'a> for InterfaceGenerator<'a> {
                 };
 
                 format!(
-                    "{access} static {name} {tag}({parameter}) {{
+                    "{access} static {name} {method_name}({parameter}) {{
                          return new {name}(Tags.{tag}, {argument});
                      }}
                     "
@@ -1571,6 +1572,15 @@ impl<'a> CoreInterfaceGenerator<'a> for InterfaceGenerator<'a> {
     }
 }
 
+// Handles the tag being the same name as the variant, which would cause a method with the same name as the type in C# which is not valid.
+pub fn variant_new_func_name(variant_name: &String, tag: &String) -> String {
+    if *tag == *variant_name {
+        format!("{tag}_") // Underscores are not valid in wit identifiers so this should be safe.
+    } else {
+        tag.clone()
+    }
+}
+
 #[derive(Copy, Clone, PartialEq, Eq, Debug)]
 pub(crate) enum ParameterType {
     ABI,

crates/test/src/cpp.rs

@@ -41,11 +41,14 @@ impl LanguageMethods for Cpp {
 
     fn should_fail_verify(
         &self,
-        _name: &str,
+        name: &str,
         config: &crate::config::WitConfig,
         _args: &[String],
     ) -> bool {
-        config.async_
+        return match name {
+            "issue1514-6.wit" => true,
+            _ => false,
+        } || config.async_;
     }
 
     fn prepare(&self, runner: &mut Runner) -> anyhow::Result<()> {

tests/codegen/issue1514-6.wit

@@ -0,0 +1,12 @@
+package demo:poc;
+
+interface i {
+  variant v {
+    v,
+  }
+  f: func(x: v);
+}
+
+world w {
+  export i;
+}