Fix integer casting of strings (lcompilers#591)

* fix str to int casting
* add test file and integration test

integration_tests/CMakeLists.txt

@@ -175,6 +175,7 @@ RUN(NAME test_issue_518      LABELS cpython llvm)
 RUN(NAME structs_01          LABELS cpython llvm c)
 RUN(NAME structs_02          LABELS llvm c)
 RUN(NAME structs_03          LABELS llvm c)
+RUN(NAME test_str_to_int     LABELS cpython llvm)
 
 # Just CPython
 RUN(NAME test_builtin_bin    LABELS cpython)

integration_tests/test_str_to_int.py

@@ -0,0 +1,10 @@
+from ltypes import i32
+
+def f():
+    i: i32
+    i = int("314")
+    assert i == 314
+    i = int("-314")
+    assert i == -314
+
+f()

src/lpython/semantics/python_ast_to_asr.cpp

@@ -3184,8 +3184,23 @@ class BodyVisitor : public CommonVisitor<BodyVisitor> {
             if (ASRUtils::expr_value(arg) != nullptr) {
                 char *c = ASR::down_cast<ASR::StringConstant_t>(
                                     ASRUtils::expr_value(arg))->m_s;
+                int ival = 0;
+                char *ch = c;
+                if (*ch == '-') {
+                    ch++;
+                }
+                while (*ch) {
+                    if (*ch == '.') {
+                        throw SemanticError("invalid literal for int() with base 10: '"+ std::string(c) + "'", arg->base.loc);
+                    }
+                    if (*ch < '0' || *ch > '9') {
+                        throw SemanticError("invalid literal for int() with base 10: '"+ std::string(c) + "'", arg->base.loc);
+                    }
+                    ch++;
+                }
+                ival = std::stoi(c);
                 return (ASR::asr_t *)ASR::down_cast<ASR::expr_t>(ASR::make_IntegerConstant_t(al,
-                                loc, std::atoi(c), to_type));
+                                loc, ival, to_type));
             }
             // TODO: make int() work for non-constant strings
         } else if (ASRUtils::is_logical(*type)) {

tests/errors/test_str_to_int.py

@@ -0,0 +1,4 @@
+def test_e1():
+    print(int('3abc'))
+
+test_e1()

tests/reference/asr-test_str_to_int-61553e7.json

@@ -0,0 +1,13 @@
+{
+    "basename": "asr-test_str_to_int-61553e7",
+    "cmd": "lpython --show-asr --no-color {infile} -o {outfile}",
+    "infile": "tests/errors/test_str_to_int.py",
+    "infile_hash": "da0ed82ada98ef2757178c4997af53abc82f4761a0e683a613216c64",
+    "outfile": null,
+    "outfile_hash": null,
+    "stdout": null,
+    "stdout_hash": null,
+    "stderr": "asr-test_str_to_int-61553e7.stderr",
+    "stderr_hash": "1998e37d9abe044f164c73ea1e000ce748ed43af5ea14c2eb4715f11",
+    "returncode": 2
+}

tests/reference/asr-test_str_to_int-61553e7.stderr

@@ -0,0 +1,5 @@
+semantic error: invalid literal for int() with base 10: '3abc'
+ --> tests/errors/test_str_to_int.py:2:15
+  |
+2 |     print(int('3abc'))
+  |               ^^^^^^ 

tests/tests.toml

@@ -534,6 +534,10 @@ asr = true
 filename = "errors/test_func_args.py"
 asr = true
 
+[[test]]
+filename = "errors/test_str_to_int.py"
+asr = true
+
 # tests/tokens/errors
 
 [[test]]