Fix a bad bounds check in component trampolines (#4716)

A `GtU` condition needed to actually be `GeU`, as the comment right
above it stated but apparently I forgot to translate the comment to
actual code. This fixes a fuzz bug that arose from oss-fuzz over the
weekend.

crates/environ/src/fact/trampoline.rs

@@ -1574,7 +1574,7 @@ impl Compiler<'_, '_> {
         // If the byte size of memory is greater than the final address of the
         // string then the string is invalid. Note that if it's precisely equal
         // then that's ok.
-        self.instruction(I64GtU);
+        self.instruction(I64GeU);
         self.instruction(BrIf(1));
 
         self.instruction(End);

crates/wasmtime/src/component/values.rs

@@ -127,7 +127,7 @@ impl fmt::Debug for Record {
     }
 }
 
-#[derive(Debug, PartialEq, Eq, Clone)]
+#[derive(PartialEq, Eq, Clone)]
 pub struct Tuple {
     ty: types::Tuple,
     values: Box<[Val]>,
@@ -166,6 +166,16 @@ impl Tuple {
     }
 }
 
+impl fmt::Debug for Tuple {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        let mut tuple = f.debug_tuple("");
+        for val in self.values() {
+            tuple.field(val);
+        }
+        tuple.finish()
+    }
+}
+
 #[derive(PartialEq, Eq, Clone)]
 pub struct Variant {
     ty: types::Variant,
@@ -227,7 +237,7 @@ impl fmt::Debug for Variant {
     }
 }
 
-#[derive(Debug, PartialEq, Eq, Clone)]
+#[derive(PartialEq, Eq, Clone)]
 pub struct Enum {
     ty: types::Enum,
     discriminant: u32,
@@ -259,7 +269,13 @@ impl Enum {
     }
 }
 
-#[derive(Debug, PartialEq, Eq, Clone)]
+impl fmt::Debug for Enum {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        fmt::Display::fmt(&self.discriminant(), f)
+    }
+}
+
+#[derive(PartialEq, Eq, Clone)]
 pub struct Union {
     ty: types::Union,
     discriminant: u32,
@@ -303,6 +319,14 @@ impl Union {
     }
 }
 
+impl fmt::Debug for Union {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        f.debug_tuple(&format!("U{}", self.discriminant()))
+            .field(self.payload())
+            .finish()
+    }
+}
+
 #[derive(PartialEq, Eq, Clone)]
 pub struct Option {
     ty: types::Option,