C2Rust fails to translate indexing on GCC/Clang vector types (`Attempting to index a vector type`)

[chisa22]

C2Rust fails to transpile a valid C program using the GCC/Clang vector_size extension when indexing a vector value.
The program defines a vector type via attribute((vector_size(16))), initializes a vector value, and then accesses one element with vec[0]. During transpilation, C2Rust skips the vector typedef due to unsupported CType::Vector, and then fails to translate main with Attempting to index a vector type.
Reproducer

#include <stdint.h>
#include <stdio.h>

int main(void) {
    typedef float v4sf __attribute__((vector_size(16)));
    v4sf vec = { 5.0f, 6.0f, 7.0f, 8.0f };
    printf("%g\n", vec[0]);
    return 0;
}

Observed Behavior
C2Rust reports:

Transpiling test.c
error: Skipping declaration Some(Typedef { name: "v4sf", typ: CQualTypeId { qualifiers: Qualifiers { is_const: false, is_restrict: false, is_volatile: false }, ctype: CTypeId(700) }, is_implicit: false, target_dependent_macro: None }) due to error: Unsupported type Vector(CQualTypeId { qualifiers: Qualifiers { is_const: false, is_restrict: false, is_volatile: false }, ctype: CTypeId(466) }, 4)

error: Failed to translate main: Attempting to index a vector type

Environment

• c2rust version: v0.21.0
• platform: Ubuntu 24.04
• Rust: nightly-2022-08-08
• Clang version: 17.0.6