fix(SSA): don't use string literal if byte is "form feed" ('\f') (#8653)

Co-authored-by: Tom French <[email protected]>

Author: asterite

compiler/noirc_evaluator/src/ssa/ir/printer.rs

@@ -338,8 +338,12 @@ fn try_byte_array_to_string(elements: &Vector<ValueId>, dfg: &DataFlowGraph) ->
         if element > 0xFF {
             return None;
         }
-        let byte = element as u8;
-        if byte.is_ascii_alphanumeric() || byte.is_ascii_punctuation() || byte.is_ascii_whitespace()
+        let byte: u8 = element as u8;
+        const FORM_FEED: u8 = 12; // This is the ASCII code for '\f', which isn't a valid escape sequence in strings
+        if byte != FORM_FEED
+            && (byte.is_ascii_alphanumeric()
+                || byte.is_ascii_punctuation()
+                || byte.is_ascii_whitespace())
         {
             string.push(byte as char);
         } else {

compiler/noirc_evaluator/src/ssa/parser/tests.rs

@@ -126,6 +126,19 @@ fn test_make_byte_slice_with_string_literal() {
     assert_ssa_roundtrip(src);
 }
 
+#[test]
+fn test_does_not_use_byte_array_literal_for_form_feed() {
+    // 12 is '\f', which isn't available in string literals (because in Rust it's the same)
+    let src = "
+        acir(inline) fn main f0 {
+          b0():
+            v1 = make_array [u8 12] : [u8; 1]
+            return v1
+        }
+        ";
+    assert_ssa_roundtrip(src);
+}
+
 #[test]
 fn test_block_parameters() {
     let src = "