Avoid call to panic_with_byte_array in simple usage of panic! (#5958)

corelib/src/byte_array.cairo

@@ -14,7 +14,7 @@ use core::zeroable::NonZeroIntoImpl;
 /// A magic constant for identifying serialization of ByteArrays. An array of felt252s with this
 /// magic as one of the felt252s indicates that right after it you should expect a serialized
 /// ByteArray. This is currently used mainly for prints and panics.
-pub(crate) const BYTE_ARRAY_MAGIC: felt252 =
+pub const BYTE_ARRAY_MAGIC: felt252 =
     0x46a6158a16a947e5916b2a2ca68501a45e93d7110e81aa2d6438b1c57c879a3;
 const BYTES_IN_U128: usize = 16;
 const BYTES_IN_BYTES31_MINUS_ONE: usize = BYTES_IN_BYTES31 - 1;

crates/cairo-lang-semantic/src/expr/expansion_test_data/inline_macros

@@ -83,3 +83,88 @@ error: Type annotations needed. Failed to infer ?0.
  --> lib.cairo:2:1
 array![]
 ^******^
+
+//! > ==========================================================================
+
+//! > Test expansion of panic macro with no arguments
+
+//! > test_runner_name
+test_expand_expr(expect_diagnostics: false)
+
+//! > expr_code
+panic!()
+
+//! > expanded_code
+core::panics::panic(array![core::byte_array::BYTE_ARRAY_MAGIC, 0, 0, 0)
+
+//! > diagnostics
+
+//! > ==========================================================================
+
+//! > Test expansion of panic macro with a simple short string
+
+//! > test_runner_name
+test_expand_expr(expect_diagnostics: false)
+
+//! > expr_code
+panic!("0123456")
+
+//! > expanded_code
+core::panics::panic(array![core::byte_array::BYTE_ARRAY_MAGIC, 0, 0x30313233343536, 7)
+
+//! > diagnostics
+
+//! > ==========================================================================
+
+//! > Test expansion of panic macro with a 31 byte string.
+
+//! > test_runner_name
+test_expand_expr(expect_diagnostics: false)
+
+//! > expr_code
+panic!("0123456789012345678901234567890")
+
+//! > expanded_code
+core::panics::panic(array![core::byte_array::BYTE_ARRAY_MAGIC, 1, 0x30313233343536373839303132333435363738393031323334353637383930, 0, 0)
+
+//! > diagnostics
+
+//! > ==========================================================================
+
+//! > Test expansion of panic macro with a simple 35 bytes string.
+
+//! > test_runner_name
+test_expand_expr(expect_diagnostics: false)
+
+//! > expr_code
+panic!("01234567890123456789012345678901234")
+
+//! > expanded_code
+core::panics::panic(array![core::byte_array::BYTE_ARRAY_MAGIC, 1, 0x30313233343536373839303132333435363738393031323334353637383930, 0x31323334, 4)
+
+//! > diagnostics
+
+//! > ==========================================================================
+
+//! > Test expansion of panic macro with args
+
+//! > test_runner_name
+test_expand_expr(expect_diagnostics: true)
+
+//! > expr_code
+panic!("bad_format(})")
+
+//! > expanded_code
+{
+    let mut __formatter_for_panic_macro__: core::fmt::Formatter = core::traits::Default::default();
+    core::result::ResultTrait::<(), core::fmt::Error>::unwrap(
+write!(__formatter_for_panic_macro__, "bad_format(})")
+    );
+    core::panics::panic_with_byte_array(@__formatter_for_panic_macro__.buffer)
+}
+
+//! > diagnostics
+error: Plugin diagnostic: Closing `}` without a matching `{`.
+ --> lib.cairo:2:8
+panic!("bad_format(})")
+       ^*************^

crates/cairo-lang-semantic/src/inline_macros/panic.rs

@@ -3,11 +3,73 @@ use cairo_lang_defs::plugin::{
     InlineMacroExprPlugin, InlinePluginResult, MacroPluginMetadata, NamedPlugin,
     PluginGeneratedFile,
 };
-use cairo_lang_defs::plugin_utils::unsupported_bracket_diagnostic;
-use cairo_lang_syntax::node::ast::WrappedArgList;
+use cairo_lang_defs::plugin_utils::{try_extract_unnamed_arg, unsupported_bracket_diagnostic};
+use cairo_lang_syntax::node::ast::{Arg, WrappedArgList};
 use cairo_lang_syntax::node::db::SyntaxGroup;
 use cairo_lang_syntax::node::{ast, TypedSyntaxNode};
 use indoc::formatdoc;
+use num_bigint::BigUint;
+
+use super::write::FELT252_BYTES;
+
+/// Try to generate a simple panic handlic code.
+/// Return true if successful and updates the buiilder if successful.
+fn try_handle_simple_panic(
+    db: &dyn SyntaxGroup,
+    builder: &mut PatchBuilder<'_>,
+    arguments: &[Arg],
+) -> bool {
+    let format_string_expr = match arguments {
+        [] => {
+            // Trivial panic!() with no arguments case.
+            builder.add_str(
+                "core::panics::panic(array![core::byte_array::BYTE_ARRAY_MAGIC, 0, 0, 0);",
+            );
+            return true;
+        }
+        [arg] => {
+            let Some(ast::Expr::String(format_string_expr)) = try_extract_unnamed_arg(db, arg)
+            else {
+                return false;
+            };
+            format_string_expr
+        }
+        // We have more than one argument, fallback to more generic handling.
+        _ => return false,
+    };
+
+    let Some(format_str) = format_string_expr.string_value(db) else {
+        return false;
+    };
+
+    if format_str.find(|c| c == '{' || c == '}').is_some() {
+        return false;
+    }
+
+    builder.add_str(&format!(
+        "core::panics::panic(array![core::byte_array::BYTE_ARRAY_MAGIC, {}, ",
+        format_str.len() / FELT252_BYTES,
+    ));
+
+    for chunk in format_str.as_bytes().chunks(FELT252_BYTES) {
+        builder.add_str(&format!("{:#x}, ", BigUint::from_bytes_be(chunk)));
+    }
+
+    let remainder_size = format_str.len() % FELT252_BYTES;
+    if remainder_size == 0 {
+        // Adding the empty remainder word.
+        builder.add_str("0, ");
+    }
+    builder.add_str(&format!("{remainder_size}))"));
+
+    builder.add_str(&format!(
+        "core::panic(array![core::byte_array::BYTE_ARRAY_MAGIC, 0, '{}', {}",
+        format_str,
+        format_str.len()
+    ));
+
+    true
+}
 
 /// Macro for panicking with a format string.
 #[derive(Default, Debug)]
@@ -25,11 +87,10 @@ impl InlineMacroExprPlugin for PanicMacro {
         let WrappedArgList::ParenthesizedArgList(arguments_syntax) = syntax.arguments(db) else {
             return unsupported_bracket_diagnostic(db, syntax);
         };
+
         let mut builder = PatchBuilder::new(db, syntax);
         let arguments = arguments_syntax.arguments(db).elements(db);
-        if arguments.is_empty() {
-            builder.add_str(r#"core::panics::panic_with_byte_array(@"")"#);
-        } else {
+        if !try_handle_simple_panic(db, &mut builder, &arguments) {
             builder.add_modified(RewriteNode::interpolate_patched(
                 &formatdoc! {
                     r#"

crates/cairo-lang-semantic/src/inline_macros/write.rs

@@ -13,6 +13,8 @@ use cairo_lang_utils::{try_extract_matches, OptionHelper};
 use indoc::indoc;
 use num_bigint::{BigInt, Sign};
 
+pub const FELT252_BYTES: usize = 31;
+
 /// Macro for writing into a formatter.
 #[derive(Debug, Default)]
 pub struct WriteMacro;
@@ -407,7 +409,6 @@ impl FormattingInfo {
         pending_chars: &mut String,
         ident_count: usize,
     ) {
-        const FELT252_BYTES: usize = 31;
         for chunk in pending_chars.as_bytes().chunks(FELT252_BYTES) {
             self.add_indentation(builder, ident_count);
             builder.add_modified(RewriteNode::interpolate_patched(