Remove equirecursive typing (#5240)

Equirecursive is no longer standards track and its implementation is extremely
complex. Remove it.

3 files changed, 7 insertions, 25 deletions

diff --git a/src/tools/tool-options.h b/src/tools/tool-options.h
index eb5212c84..0522b5538 100644
--- a/src/tools/tool-options.h
+++ b/src/tools/tool-options.h
@@ -148,15 +148,6 @@ struct ToolOptions : public Options {
            [](Options* o, const std::string& argument) {
              setTypeSystem(TypeSystem::Nominal);
            })
-      .add("--structural",
-           "",
-           "Force all GC type definitions to be parsed as structural "
-           "(i.e. equirecursive). This is the default.",
-           ToolOptionsCategory,
-           Options::Arguments::Zero,
-           [](Options* o, const std::string& argument) {
-             setTypeSystem(TypeSystem::Equirecursive);
-           })
       .add("--hybrid",
            "",
            "Force all GC type definitions to be parsed using the isorecursive "
@@ -196,9 +187,7 @@ struct ToolOptions : public Options {
   void applyFeatures(Module& module) const {
     module.features.enable(enabledFeatures);
     module.features.disable(disabledFeatures);
-    // Non-default type systems only make sense with GC enabled. TODO: Error on
-    // non-GC equirecursive types as well once we make isorecursive the default
-    // if we don't remove equirecursive types entirely.
+    // Non-default type systems only make sense with GC enabled.
     if (!module.features.hasGC() && getTypeSystem() == TypeSystem::Nominal) {
       Fatal() << "Nominal typing is only allowed when GC is enabled";
     }
diff --git a/src/tools/wasm-fuzz-types.cpp b/src/tools/wasm-fuzz-types.cpp
index bbf4967e3..0e40e7a15 100644
--- a/src/tools/wasm-fuzz-types.cpp
+++ b/src/tools/wasm-fuzz-types.cpp
@@ -517,25 +517,17 @@ int main(int argc, const char* argv[]) {
               Options::Arguments::Zero,
               [&](Options*, const std::string& arg) { verbose = true; });
 
-  TypeSystem system = TypeSystem::Nominal;
+  TypeSystem system = TypeSystem::Isorecursive;
   options.add(
     "--nominal",
     "",
-    "Use the nominal type system (default)",
+    "Use the nominal type system",
     WasmFuzzTypesOption,
     Options::Arguments::Zero,
     [&](Options*, const std::string& arg) { system = TypeSystem::Nominal; });
-  options.add("--structural",
-              "",
-              "Use the equirecursive type system",
-              WasmFuzzTypesOption,
-              Options::Arguments::Zero,
-              [&](Options*, const std::string& arg) {
-                system = TypeSystem::Equirecursive;
-              });
   options.add("--hybrid",
               "",
-              "Use the isorecursive hybrid type system",
+              "Use the isorecursive hybrid type system (default)",
               WasmFuzzTypesOption,
               Options::Arguments::Zero,
               [&](Options*, const std::string& arg) {
diff --git a/src/tools/wasm-reduce.cpp b/src/tools/wasm-reduce.cpp
index eec1e0874..d92e0a93c 100644
--- a/src/tools/wasm-reduce.cpp
+++ b/src/tools/wasm-reduce.cpp
@@ -1293,9 +1293,10 @@ int main(int argc, const char* argv[]) {
   }
   if (getTypeSystem() == TypeSystem::Nominal) {
     extraFlags += " --nominal";
-  }
-  if (getTypeSystem() == TypeSystem::Isorecursive) {
+  } else if (getTypeSystem() == TypeSystem::Isorecursive) {
     extraFlags += " --hybrid";
+  } else {
+    WASM_UNREACHABLE("unexpected type system");
   }
 
   if (test.size() == 0) {