Support string repeat with non constant integer (#2675)

* Support string repeat with non-constant integer

* Tests: Add tests

* Set character `a_len` to -1

Co-authored-by: Shaikh Ubaid <shaikhubaid769@gmail.com>

* Simplify conditional check to `else`

* Handle negative integers for string repeat

* Tests: Update test

---------

Co-authored-by: Shaikh Ubaid <shaikhubaid769@gmail.com>

Author: kmr-srbh

integration_tests/test_str_01.py

@@ -1,3 +1,5 @@
+from lpython import i32
+
 def f():
     x: str
     x = "ok"
@@ -58,9 +60,38 @@ def test_str_repeat():
     assert a*3 == "XyzXyzXyz"
     assert a*2*3 == "XyzXyzXyzXyzXyzXyz"
     assert 3*a*3 == "XyzXyzXyzXyzXyzXyzXyzXyzXyz"
-    assert a*-1 == ""
+    b: str = a * -1
+    assert b == ""
     assert len(a*(10**6)) == (3 * 10 ** 6)
 
+    # string repeat with a non-constant integer
+    s: str = "#"
+    n: i32 = 5
+
+    assert s * n == "#####"
+    assert n * s == "#####"
+
+    assert "@" * n == "@@@@@"
+    assert "@#$%" * n == "@#$%@#$%@#$%@#$%@#$%"
+
+    s = "@#$%"
+    assert n * s == "@#$%@#$%@#$%@#$%@#$%"
+
+    n = 10 ** 6
+    assert len(s * n) == (4 * 10 ** 6)
+
+    s = "$"
+    m: i32 = 2
+    n = 5
+    t: str = s * m * n
+    assert t == "$$$$$$$$$$"
+    assert s * m * 2 == "$$$$"
+    assert 2 * (m + n) * s == "$$$$$$$$$$$$$$"
+
+    t = 2 * (m + n) * "abc-"
+    assert t == "abc-abc-abc-abc-abc-abc-abc-abc-abc-abc-abc-abc-abc-abc-"
+
+
 def test_str_join():
     a: str
     a = ","

src/libasr/runtime/lfortran_intrinsics.c

@@ -2140,7 +2140,7 @@ LFORTRAN_API void _lfortran_strrepeat(char** s, int32_t n, char** dest)
     char* dest_char = (char*)malloc(f_len+trmn_size);
 
     if (s_len == 1) {
-        memset(dest_char, *(*s), n);
+        memset(dest_char, *(*s), f_len);
     } else {
         memcpy(dest_char, *s, s_len);
         int chars_copied = s_len;

src/lpython/semantics/python_ast_to_asr.cpp

@@ -2079,7 +2079,7 @@ class CommonVisitor : public AST::BaseVisitor<Struct> {
         } else if ((right_is_int || left_is_int) && op == ASR::binopType::Mul) {
             // string repeat
             int64_t left_int = 0, right_int = 0, dest_len = 0;
-            if (right_is_int) {
+            if (right_is_int && ASRUtils::expr_value(right) != nullptr) {
                 ASR::Character_t *left_type2 = ASR::down_cast<ASR::Character_t>(
                     ASRUtils::type_get_past_array(left_type));
                 LCOMPILERS_ASSERT(ASRUtils::extract_n_dims_from_ttype(left_type) == 0);
@@ -2090,7 +2090,7 @@ class CommonVisitor : public AST::BaseVisitor<Struct> {
                 dest_type = ASR::down_cast<ASR::ttype_t>(
                         ASR::make_Character_t(al, loc, left_type2->m_kind,
                         dest_len, nullptr));
-            } else if (left_is_int) {
+            } else if (left_is_int && ASRUtils::expr_value(left) != nullptr) {
                 ASR::Character_t *right_type2 = ASR::down_cast<ASR::Character_t>(
                     ASRUtils::type_get_past_array(right_type));
                 LCOMPILERS_ASSERT(ASRUtils::extract_n_dims_from_ttype(right_type) == 0);
@@ -2101,6 +2101,9 @@ class CommonVisitor : public AST::BaseVisitor<Struct> {
                 dest_type = ASR::down_cast<ASR::ttype_t>(
                         ASR::make_Character_t(al, loc, right_type2->m_kind,
                         dest_len, nullptr));
+            } else {
+                dest_type = ASRUtils::TYPE(ASR::make_Character_t(al,
+                            loc, 1, -1, nullptr));
             }
 
             if (ASRUtils::expr_value(left) != nullptr && ASRUtils::expr_value(right) != nullptr) {