From 6945f7c572449bd86a78acaf4add373609536cca Mon Sep 17 00:00:00 2001
From: Alex Crichton <alex@alexcrichton.com>
Date: Mon, 9 Feb 2026 10:57:46 -0800
Subject: [PATCH] Fix fuzzing with `stream<char>`

Fallout from #2437 in fuzzing where it needs to not be generated any
more.
---
 Cargo.lock                  |  1 +
 crates/wit-smith/Cargo.toml |  1 +
 crates/wit-smith/src/lib.rs | 15 ++++++++++++++-
 3 files changed, 16 insertions(+), 1 deletion(-)

diff --git a/Cargo.lock b/Cargo.lock
index cafb36e158..0f6b3025c9 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -3197,6 +3197,7 @@ dependencies = [
  "indexmap 2.10.0",
  "log",
  "semver",
+ "wasmparser 0.244.0",
  "wit-component 0.244.0",
  "wit-parser 0.244.0",
 ]
diff --git a/crates/wit-smith/Cargo.toml b/crates/wit-smith/Cargo.toml
index 34f8ff526a..05765692b0 100644
--- a/crates/wit-smith/Cargo.toml
+++ b/crates/wit-smith/Cargo.toml
@@ -19,3 +19,4 @@ log = { workspace = true }
 semver = { workspace = true }
 wit-component = { workspace = true }
 wit-parser = { workspace = true }
+wasmparser = { workspace = true }
diff --git a/crates/wit-smith/src/lib.rs b/crates/wit-smith/src/lib.rs
index 6078287fb0..ebc0e09fa2 100644
--- a/crates/wit-smith/src/lib.rs
+++ b/crates/wit-smith/src/lib.rs
@@ -42,5 +42,18 @@ pub fn smith(config: &Config, u: &mut Unstructured<'_>) -> Result<Vec<u8>> {
     }
     let pkg = last.unwrap();
 
-    Ok(wit_component::encode(&resolve, pkg).expect("failed to encode WIT document"))
+    let wasm = wit_component::encode(&resolve, pkg).expect("failed to encode WIT document");
+
+    // Handle disallowing `stream<char>` here vs not generating it to start
+    // with as it's a bit easier to handle.
+    if let Err(e) = wasmparser::Validator::new_with_features(wasmparser::WasmFeatures::all())
+        .validate_all(&wasm)
+    {
+        if e.to_string()
+            .contains("`stream<char>` is not valid at this time")
+        {
+            return Err(arbitrary::Error::IncorrectFormat);
+        }
+    }
+    Ok(wasm)
 }