Add underscore separators for large numbers in reporting

reporting/src/error/canonicalize.rs

@@ -1141,16 +1141,24 @@ fn pretty_runtime_error<'b>(
             let (big_or_small, info) = if let IntErrorKind::Underflow = error_kind {
                 (
                     "small",
-                    alloc.reflow(
+                    alloc.concat(vec![
-                        "The smallest number representable in Roc is the minimum I128 value, -170_141_183_460_469_231_731_687_303_715_884_105_728.",
+                        alloc.reflow(
-                    ),
+                            "The smallest number representable in Roc is the minimum I128 value, ",
+                        ),
+                        alloc.int_literal(i128::MIN),
+                        alloc.text("."),
+                    ]),
                 )
             } else {
                 (
                     "big",
-                    alloc.reflow(
+                    alloc.concat(vec![
-                        "The largest number representable in Roc is the maximum U128 value, 340_282_366_920_938_463_463_374_607_431_768_211_455.",
+                        alloc.reflow(
-                    ),
+                            "The largest number representable in Roc is the maximum U128 value, ",
+                        ),
+                        alloc.int_literal(u128::MAX),
+                        alloc.text("."),
+                    ]),
                 )
             };
 
@@ -1199,7 +1207,8 @@ fn pretty_runtime_error<'b>(
                     alloc.reflow("The suffix indicates this integer is a "),
                     alloc.type_str(suffix_type),
                     alloc.reflow(", whose maximum value is "),
-                    alloc.text(format!("{}.", max_value)),
+                    alloc.int_literal(max_value),
+                    alloc.reflow("."),
                 ])),
             ]);
 
@@ -1223,7 +1232,8 @@ fn pretty_runtime_error<'b>(
                     alloc.reflow("The suffix indicates this integer is a "),
                     alloc.type_str(suffix_type),
                     alloc.reflow(", whose minimum value is "),
-                    alloc.text(format!("{}.", min_value)),
+                    alloc.int_literal(min_value),
+                    alloc.reflow("."),
                 ])),
             ]);
 

reporting/src/report.rs

@@ -632,6 +632,39 @@ impl<'a> RocDocAllocator<'a> {
         self.text(format!("{}", ident.as_inline_str()))
             .annotate(Annotation::Symbol)
     }
+
+    pub fn int_literal<I>(&'a self, int: I) -> DocBuilder<'a, Self, Annotation>
+    where
+        I: ToString,
+    {
+        let s = int.to_string();
+
+        let is_negative = s.starts_with("-");
+
+        if s.len() < 7 + (is_negative as usize) {
+            // If the number is not at least in the millions, return it as-is.
+            return self.text(s);
+        }
+
+        // Otherwise, let's add numeric separators to make it easier to read.
+        let mut result = String::with_capacity(s.len() + s.len() / 3);
+        for (idx, c) in s
+            .get((is_negative as usize)..)
+            .unwrap()
+            .chars()
+            .rev()
+            .enumerate()
+        {
+            if idx != 0 && idx % 3 == 0 {
+                result.push('_');
+            }
+            result.push(c);
+        }
+        if is_negative {
+            result.push('-');
+        }
+        self.text(result.chars().rev().collect::<String>())
+    }
 }
 
 #[derive(Copy, Clone)]

reporting/tests/test_reporting.rs

@@ -7622,7 +7622,7 @@ I need all branches in an `if` to have the same type!
                     ^^^^^^^^^^^^^^^^
 
                 Tip: The suffix indicates this integer is a U32, whose maximum value
-                is 4294967295.
+                is 4_294_967_295.
                 "#
             ),
         )
@@ -7662,7 +7662,7 @@ I need all branches in an `if` to have the same type!
                     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
                 Tip: The suffix indicates this integer is a U64, whose maximum value
-                is 18446744073709551615.
+                is 18_446_744_073_709_551_615.
                 "#
             ),
         )
@@ -7802,7 +7802,7 @@ I need all branches in an `if` to have the same type!
                     ^^^^^^^^^^^^^^^^
 
                 Tip: The suffix indicates this integer is a I32, whose maximum value
-                is 2147483647.
+                is 2_147_483_647.
                 "#
             ),
         )
@@ -7822,7 +7822,7 @@ I need all branches in an `if` to have the same type!
                     ^^^^^^^^^^^^^^^^^
 
                 Tip: The suffix indicates this integer is a I32, whose minimum value
-                is -2147483648.
+                is -2_147_483_648.
                 "#
             ),
         )
@@ -7842,7 +7842,7 @@ I need all branches in an `if` to have the same type!
                     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
                 Tip: The suffix indicates this integer is a I64, whose maximum value
-                is 9223372036854775807.
+                is 9_223_372_036_854_775_807.
                 "#
             ),
         )
@@ -7862,7 +7862,7 @@ I need all branches in an `if` to have the same type!
                     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
                 Tip: The suffix indicates this integer is a I64, whose minimum value
-                is -9223372036854775808.
+                is -9_223_372_036_854_775_808.
                 "#
             ),
         )
@@ -7882,7 +7882,7 @@ I need all branches in an `if` to have the same type!
                     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
                 Tip: The suffix indicates this integer is a I128, whose maximum value
-                is 170141183460469231731687303715884105727.
+                is 170_141_183_460_469_231_731_687_303_715_884_105_727.
                 "#
             ),
         )