Add compile-time support for dict.keys (lcompilers#2660)

* Implement `dict.keys` for `DictConstant`

* Tests: Add tests and update references

* Tests: Update test

* Uncomment check for modifying attributes

* Tests: Update test references

* Delete tests/reference/asr-func_04-eef2656.stdout

* Style changes

Co-authored-by: Shaikh Ubaid <[email protected]>

* Style changes

Co-authored-by: Shaikh Ubaid <[email protected]>

* Tests: Move `print` before `assert`

---------

Co-authored-by: Shaikh Ubaid <[email protected]>

Author: 2 people

integration_tests/test_dict_keys_values.py

@@ -51,4 +51,27 @@ def test_dict_keys_values():
                 assert v2_copy[j] == d2[str(i)]
         assert key_count == 1
 
+
+    # dict.keys on dict constant
+    print({1: "a"}.keys())
+    assert len({1: "a"}.keys()) == 1
+
+    print({"a": 1, "b": 2, "c": 3}.keys())
+    assert len({"a": 1, "b": 2, "c": 3}.keys()) == 3
+
+    print({1: [1, 2, 3], 2: [4, 5, 6], 3: [7, 8, 9]}.keys())
+    assert len({1: [1, 2, 3], 2: [4, 5, 6], 3: [7, 8, 9]}.keys()) == 3
+
+    print({(1, 2): "a", (3, 4): "b", (5, 6): "c"}.keys())
+    assert len({(1, 2): "a", (3, 4): "b", (5, 6): "c"}.keys()) == 3
+
+    k_1: list[str] = {"list1": [1, 2, 3], "list2": [4, 5, 6], "list3": [7, 8, 9]}.keys()
+    print(k_1)
+    assert len(k_1) == 3
+
+    k_2: list[tuple[i32, i32]] = {(1, 2): "a", (3, 4): "b", (5, 6): "c"}.keys()
+    print(k_2)
+    assert len(k_2) == 3
+
+
 test_dict_keys_values()

src/libasr/pass/intrinsic_functions.h

@@ -4734,10 +4734,15 @@ static inline void verify_args(const ASR::IntrinsicElementalFunction_t& x, diag:
         x.base.base.loc, diagnostics);
 }
 
-static inline ASR::expr_t *eval_dict_keys(Allocator &/*al*/,
-    const Location &/*loc*/, ASR::ttype_t *, Vec<ASR::expr_t*>& /*args*/, diag::Diagnostics& /*diag*/) {
-    // TODO: To be implemented for DictConstant expression
-    return nullptr;
+static inline ASR::expr_t *eval_dict_keys(Allocator &al,
+    const Location &loc, ASR::ttype_t *t, Vec<ASR::expr_t*>& args, diag::Diagnostics& /*diag*/) {
+        if (args[0] == nullptr) {
+            return nullptr;
+        }
+        ASR::DictConstant_t* cdict = ASR::down_cast<ASR::DictConstant_t>(args[0]);
+
+        return ASRUtils::EXPR(ASR::make_ListConstant_t(al, loc,
+            cdict->m_keys, cdict->n_keys, t));
 }
 
 static inline ASR::asr_t* create_DictKeys(Allocator& al, const Location& loc,

src/lpython/semantics/python_ast_to_asr.cpp

@@ -7689,6 +7689,20 @@ we will have to use something else.
                     }
                 }
             }
+        } else if (AST::is_a<AST::Dict_t>(*at->m_value)) {
+            AST::Dict_t* cdict = AST::down_cast<AST::Dict_t>(at->m_value);
+            visit_Dict(*cdict);
+            if (tmp == nullptr) {
+                throw SemanticError("cannot call " + std::string(at->m_attr) + " on an empty dict" , loc);
+            }
+            ASR::expr_t* dict_expr = ASR::down_cast<ASR::expr_t>(tmp);
+            Vec<ASR::expr_t*> eles;
+            eles.reserve(al, args.size());
+            for (size_t i = 0; i < args.size(); i++) {
+                eles.push_back(al, args[i].m_value);
+            }
+            handle_builtin_attribute(dict_expr, at->m_attr, loc, eles);
+            return;
         } else {
             throw SemanticError("Only Name type and constant integers supported in Call", loc);
         }