Misleading error message

[rebcabin]

from numpy import empty, int16

from lpython import (i16, i32, CPtr, ccall, sizeof)


@ccall
def _lfortran_malloc(size : i32) -> CPtr:
    """borrowed from bindc_07.py in integration_tests"""
    pass


def main():
    n  : i32 = 15  # <~~~~~~~~~~~ LOOKS LIKE COMPILE-TIME CONSTANT ??? ~~~~~~~~~~
    m  : i32 = 3

    # Emulate getting stuff from the C side.
    Anm_l4 : CPtr = _lfortran_malloc( (n * m) * i32(sizeof(i16)) )
    A_nm: i16[n, m] = empty((n, m), dtype=int16)


if __name__ == "__main__":
    main()

(lp) ┌─(~/Documents/GitHub/lpython/integration_tests)────(brian@MacBook-Pro:s001)─┐
└─(12:16:55 on vector-backend ✹ ✭)──> lpython ../ISSUES/UNHANDLED-EXCEPTIONS/Issue2492.py                                              2 ↵ ──(Tue,Feb06)─┘
semantic error: Only those local variables which can be reduced to compile time constant should be used in dimensions of an array.
  --> ../ISSUES/UNHANDLED-EXCEPTIONS/Issue2492.py:18:15
   |
18 |     A_nm: i16[n, m] = empty((n, m), dtype=int16)
   |               ^ 

[rebcabin]

Some more possibilities:

    # The following does not work in lpython (Issue #2492)
    # A_nm: i16[n, m] = empty((n, m), dtype=int16)
    # doesn't work
    # A_nm : i16[:] = empty((n, m), dtype=int16)
    # works!
    A_nm : Allocatable[i16[:]] = empty((n, m), dtype=int16)

[rebcabin]

The following produces an unhandled exception

    A_nm : Array[i16[:]] = empty((n, m), dtype=int16)

(lp) ┌─(~/Documents/GitHub/lpython/integration_tests)────────────────────────────────────────────────────────────────────────────────(brian@MacBook-Pro:s001)─┐
└─(12:48:58 on vector-backend ✹ ✭)──> lpython matmul_integration.py                                                                        ──(Tue,Feb06)─┘
Internal Compiler Error: Unhandled exception
Traceback (most recent call last):
  File "/Users/brian/Dropbox/Mac/Documents/GitHub/lpython/src/bin/lpython.cpp", line 1872
    err = compile_python_to_object_file(arg_file, tmp_o, runtime_library_dir,
  File "/Users/brian/Dropbox/Mac/Documents/GitHub/lpython/src/bin/lpython.cpp", line 786
    r1 = LCompilers::LPython::python_ast_to_asr(al, lm, nullptr, *ast, diagnostics, compiler_options,
  File "/Users/brian/Dropbox/Mac/Documents/GitHub/lpython/src/lpython/semantics/python_ast_to_asr.cpp", line 7996
    auto res2 = body_visitor(al, lm, *ast_m, diagnostics, unit, main_module, module_name,
  File "/Users/brian/Dropbox/Mac/Documents/GitHub/lpython/src/lpython/semantics/python_ast_to_asr.cpp", line 7932
    BodyVisitor b(al, lm, unit, diagnostics, main_module, module_name, ast_overload, allow_implicit_casting);
  File "/Users/brian/Dropbox/Mac/Documents/GitHub/lpython/src/lpython/semantics/python_ast_to_asr.cpp", line 4713
    visit_stmt(*x.m_body[i]);
  File "/Users/brian/Dropbox/Mac/Documents/GitHub/lpython/src/lpython/python_ast.h", line 1883
    void visit_stmt(const stmt_t &b) { visit_stmt_t(b, self()); }
  File "/Users/brian/Dropbox/Mac/Documents/GitHub/lpython/src/lpython/python_ast.h", line 1751
    case stmtType::FunctionDef: { v.visit_FunctionDef((const FunctionDef_t &)x); return; }
  File "/Users/brian/Dropbox/Mac/Documents/GitHub/lpython/src/lpython/semantics/python_ast_to_asr.cpp", line 4814
    handle_fn(x, *f);
  File "/Users/brian/Dropbox/Mac/Documents/GitHub/lpython/src/lpython/semantics/python_ast_to_asr.cpp", line 4790
    transform_stmts(body, x.n_body, x.m_body);
  File "/Users/brian/Dropbox/Mac/Documents/GitHub/lpython/src/lpython/semantics/python_ast_to_asr.cpp", line 4667
    this->visit_stmt(*m_body[i]);
  File "/Users/brian/Dropbox/Mac/Documents/GitHub/lpython/src/lpython/python_ast.h", line 1883
    void visit_stmt(const stmt_t &b) { visit_stmt_t(b, self()); }
  File "/Users/brian/Dropbox/Mac/Documents/GitHub/lpython/src/lpython/python_ast.h", line 1757
    case stmtType::AugAssign: { v.visit_AugAssign((const AugAssign_t &)x); return; }
  File "/Users/brian/Dropbox/Mac/Documents/GitHub/lpython/src/lpython/semantics/python_ast_to_asr.cpp", line 4885
    visit_AnnAssignUtil(x, var_name, init_expr);
  File "/Users/brian/Dropbox/Mac/Documents/GitHub/lpython/src/lpython/semantics/python_ast_to_asr.cpp", line 2785
    type = ast_expr_to_asr_type(x.m_annotation->base.loc, *x.m_annotation, is_allocatable, true, abi);
  File "/Users/brian/Dropbox/Mac/Documents/GitHub/lpython/src/lpython/semantics/python_ast_to_asr.cpp", line 1739
    LCOMPILERS_ASSERT(AST::is_a<AST::Tuple_t>(*s->m_slice));
AssertFailed: AST::is_a<AST::Tuple_t>(*s->m_slice)

[ubaidsk]

We need to declare the variables m, n as constants. For example:

% cat examples/expr2.py 
from lpython import i16, i32, Const
from numpy import empty, int16

def main():
    n  : Const[i32] = 15  # <~~~~~~~~~~~ LOOKS LIKE COMPILE-TIME CONSTANT ??? ~~~~~~~~~~
    m  : Const[i32] = 3

    # Emulate getting stuff from the C side.
    A_nm: i16[n, m] = empty((n, m), dtype=int16)
    print(A_nm.size)

if __name__ == "__main__":
   main()
% python examples/expr2.py 
45
% lpython examples/expr2.py
45

[rebcabin]

Thanks! I'm leaving it open because of the uncaught exception, but your answer with Const unblocks my work!