Better hint for non-zero em length (#4873)

Co-authored-by: Laurenz <laurmaedje@gmail.com>

2 files changed, 17 insertions, 10 deletions

diff --git a/crates/typst/src/layout/length.rs b/crates/typst/src/layout/length.rs
index 8c883a6a..5e352f13 100644
--- a/crates/typst/src/layout/length.rs
+++ b/crates/typst/src/layout/length.rs
@@ -5,7 +5,7 @@ use std::ops::{Add, Div, Mul, Neg};
 use comemo::Tracked;
 use ecow::{eco_format, EcoString};
 
-use crate::diag::{At, Hint, HintedStrResult, SourceResult};
+use crate::diag::{bail, HintedStrResult, SourceResult};
 use crate::foundations::{func, scope, ty, Context, Fold, Repr, Resolve, StyleChain};
 use crate::layout::{Abs, Em};
 use crate::syntax::Span;
@@ -81,12 +81,15 @@ impl Length {
         if self.em == Em::zero() {
             return Ok(());
         }
-        Err(eco_format!(
+
+        bail!(
+            span,
             "cannot convert a length with non-zero em units (`{}`) to {unit}",
-            self.repr()
-        ))
-        .hint(eco_format!("use `length.abs.{unit}()` instead to ignore its em component"))
-        .at(span)
+            self.repr();
+            hint: "use `length.to-absolute()` to resolve its em component \
+                   (requires context)";
+            hint: "or use `length.abs.{unit}()` instead to ignore its em component"
+        )
     }
 }
 
diff --git a/tests/suite/layout/length.typ b/tests/suite/layout/length.typ
index 34a4b939..c40752f7 100644
--- a/tests/suite/layout/length.typ
+++ b/tests/suite/layout/length.typ
@@ -51,20 +51,24 @@
 
 --- length-ignore-em-pt-hint ---
 // Error: 2-21 cannot convert a length with non-zero em units (`-6pt + 10.5em`) to pt
-// Hint: 2-21 use `length.abs.pt()` instead to ignore its em component
+// Hint: 2-21 use `length.to-absolute()` to resolve its em component (requires context)
+// Hint: 2-21 or use `length.abs.pt()` instead to ignore its em component
 #(10.5em - 6pt).pt()
 
 --- length-ignore-em-cm-hint ---
 // Error: 2-12 cannot convert a length with non-zero em units (`3em`) to cm
-// Hint: 2-12 use `length.abs.cm()` instead to ignore its em component
+// Hint: 2-12 use `length.to-absolute()` to resolve its em component (requires context)
+// Hint: 2-12 or use `length.abs.cm()` instead to ignore its em component
 #(3em).cm()
 
 --- length-ignore-em-mm-hint ---
 // Error: 2-20 cannot convert a length with non-zero em units (`-226.77pt + 93em`) to mm
-// Hint: 2-20 use `length.abs.mm()` instead to ignore its em component
+// Hint: 2-20 use `length.to-absolute()` to resolve its em component (requires context)
+// Hint: 2-20 or use `length.abs.mm()` instead to ignore its em component
 #(93em - 80mm).mm()
 
 --- length-ignore-em-inches-hint ---
 // Error: 2-24 cannot convert a length with non-zero em units (`432pt + 4.5em`) to inches
-// Hint: 2-24 use `length.abs.inches()` instead to ignore its em component
+// Hint: 2-24 use `length.to-absolute()` to resolve its em component (requires context)
+// Hint: 2-24 or use `length.abs.inches()` instead to ignore its em component
 #(4.5em + 6in).inches()