Creating vector.kk with an identifier named empty gives a strange compiler error

[chtenb]

1. Create vector.kk
2. Add pub val empty : forall<a> vector<a> = unit/vector()
3. Compile

(Changing the name of the file, or adding a qualifier to empty makes the error disappear)

check   : vector
In file included from .koka/v3.1.3/clang-cl-debug-29abf8/vector.c:2:
.koka/v3.1.3/clang-cl-debug-29abf8\vector.h(31,20): error: redefinition of 'kk_vector_empty' as different kind of
      symbol
   31 | extern kk_vector_t kk_vector_empty;
      |                    ^
c:/Users/ChieltenBrinke/prj/koka/kklib/include\kklib/vector.h(23,41): note: previous definition is here
   23 | static inline kk_decl_const kk_vector_t kk_vector_empty(void) {
      |                                         ^
.koka/v3.1.3/clang-cl-debug-29abf8/vector.c(4,13): error: redefinition of 'kk_vector_empty' as different kind of symbol
    4 | kk_vector_t kk_vector_empty;
      |             ^
c:/Users/ChieltenBrinke/prj/koka/kklib/include\kklib/vector.h(23,41): note: previous definition is here
   23 | static inline kk_decl_const kk_vector_t kk_vector_empty(void) {
      |                                         ^
.koka/v3.1.3/clang-cl-debug-29abf8/vector.c(35,21): error: non-object type 'kk_vector_t ()' (aka 'kk_datatype_s ()') is
      not assignable
   35 |     kk_vector_empty = kk_vector_empty(); /*forall<a> vector<a>*/
      |     ~~~~~~~~~~~~~~~ ^
.koka/v3.1.3/clang-cl-debug-29abf8/vector.c(47,3): error: no matching function for call to 'kk_vector_drop'
   47 |   kk_vector_drop(kk_vector_empty, _ctx);
      |   ^~~~~~~~~~~~~~
c:/Users/ChieltenBrinke/prj/koka/kklib/include\kklib/vector.h(36,20): note: candidate function not viable: no known
      conversion from 'kk_vector_t ()' (aka 'kk_datatype_s ()') to 'kk_vector_t' (aka 'kk_datatype_s') for 1st argument
   36 | static inline void kk_vector_drop(kk_vector_t v, kk_context_t* ctx) {
      |                    ^              ~~~~~~~~~~~~~
4 errors generated.
vector(1, 1): build error: user error (error  : command failed (exit code 1)
command: "c:/Program Files/LLVM/bin/clang-cl.exe" -DWIN32 -nologo -Wno-everything -Wall -Wextra -Wpointer-arith -Wshadow -Wstrict-aliasing -Wno-unknown-pragmas -Wno-missing-field-initializers -Wno-unused-parameter -Wno-unused-variable -Wno-unused-value -Wno-cast-qual -Wno-undef -Wno-reserved-id-macro -Wno-unused-macros -Wno-cast-align -Wno-extra-semi-stmt -Wno-extra-semi -Wno-float-equal -MDd -Zi -FS -O1 -D__clang_msvc__ -EHs -TP -c -I c:/Users/ChieltenBrinke/prj/koka/kklib/include -DKK_MIMALLOC=8 -Fo.koka/v3.1.3/clang-cl-debug-29abf8/vector.obj .koka/v3.1.3/clang-cl-debug-29abf8/vector.c)

Failed to compile vector.kk

[TimWhiting]

Unfortunately this is a pretty hard thing to fix.

We don't want to mangle all the names in the program, because that would make C interop harder. At the same time, we do have some c definitions already. So you just happened to give your function a name that translates to kk_vector_empty (kk + file name + definition name). which is already defined in our core libraries for use with the unit/vector constructor:

// Create an empty vector.
pub inline extern unit/vector : forall<a> () -> vector<a>
  c inline "kk_vector_empty()"
  cs inline "new ##1[0]"
  js inline "[]"

To fix this we have a few options:

• we rely on people parsing the C error message (do nothing),
• we have to keep a list of all the C definitions in our core libraries and dependencies in the compiler and throw a message,
• or we have to adopt a different naming system for core libraries versus for user generated code

Both of the last two are possible, but would require lots of renaming and fixing our extern definitions, or a large initial effort to document all C definitions, and a continual effort to keep that list maintained. (Also we have no guarantee that other people won't add their own C libraries and extern definitions that might conflict).