Suggest typo fixes for non-existing module values

compiler/can/src/env.rs

@@ -1,6 +1,6 @@
 use crate::procedure::References;
 use roc_collections::all::{MutMap, MutSet};
-use roc_module::ident::{Ident, ModuleName};
+use roc_module::ident::{Ident, Lowercase, ModuleName};
 use roc_module::symbol::{IdentIds, ModuleId, ModuleIds, Symbol};
 use roc_problem::can::{Problem, RuntimeError};
 use roc_region::all::{Located, Region};
@@ -99,11 +99,8 @@ impl<'a> Env<'a> {
                         )),
                     }
                 } else {
-                    match self
-                        .dep_idents
-                        .get(&module_id)
-                        .and_then(|exposed_ids| exposed_ids.get_id(&ident))
-                    {
+                    match self.dep_idents.get(&module_id) {
+                        Some(exposed_ids) => match exposed_ids.get_id(&ident) {
                             Some(ident_id) => {
                                 let symbol = Symbol::new(module_id, *ident_id);
 
@@ -111,11 +108,33 @@ impl<'a> Env<'a> {
 
                                 Ok(symbol)
                             }
-                        None => Err(RuntimeError::ValueNotExposed {
+                            None => {
+                                let exposed_values = exposed_ids
+                                    .idents()
+                                    .filter(|(_, ident)| {
+                                        ident
+                                            .as_ref()
+                                            .chars()
+                                            .next()
+                                            .filter(|c| c.is_lowercase())
+                                            .is_some()
+                                    })
+                                    .map(|(_, ident)| Lowercase::from(ident.as_ref()))
+                                    .collect();
+                                Err(RuntimeError::ValueNotExposed {
                                     module_name,
                                     ident,
                                     region,
-                        }),
+                                    exposed_values,
+                                })
+                            }
+                        },
+                        None => {
+                            panic!(
+                                "Module {} exists, but is not recorded in dep_idents",
+                                module_name
+                            )
+                        }
                     }
                 }
             }

compiler/problem/src/can.rs

@@ -139,6 +139,7 @@ pub enum RuntimeError {
         module_name: ModuleName,
         ident: Ident,
         region: Region,
+        exposed_values: Vec<Lowercase>,
     },
     ModuleNotImported {
         module_name: ModuleName,

reporting/src/error/canonicalize.rs

@@ -6,6 +6,7 @@ use roc_problem::can::{BadPattern, FloatErrorKind, IntErrorKind, Problem, Runtim
 use roc_region::all::{Located, Region};
 use std::path::PathBuf;
 
+use crate::error::r#type::suggest;
 use crate::report::{Annotation, Report, RocDocAllocator, RocDocBuilder, Severity};
 use ven_pretty::DocAllocator;
 
@@ -874,16 +875,36 @@ fn pretty_runtime_error<'b>(
             module_name,
             ident,
             region,
+            exposed_values,
         } => {
+            let mut suggestions = suggest::sort(ident.as_ref(), exposed_values);
+            suggestions.truncate(4);
+
+            let did_you_mean = if suggestions.is_empty() {
+                alloc.concat(vec![
+                    alloc.reflow("In fact, it look like "),
+                    alloc.module_name(module_name.clone()),
+                    alloc.reflow(" doesn't expose any values!"),
+                ])
+            } else {
+                let qualified_suggestions = suggestions
+                    .into_iter()
+                    .map(|v| alloc.string(module_name.to_string() + "." + v.as_str()));
+                alloc.stack(vec![
+                    alloc.reflow("Did you mean one of these?"),
+                    alloc.vcat(qualified_suggestions).indent(4),
+                ])
+            };
             doc = alloc.stack(vec![
                 alloc.concat(vec![
                     alloc.reflow("The "),
                     alloc.module_name(module_name),
-                    alloc.reflow(" module does not expose a "),
+                    alloc.reflow(" module does not expose `"),
                     alloc.string(ident.to_string()),
-                    alloc.reflow(" value:"),
+                    alloc.reflow("`:"),
                 ]),
                 alloc.region(region),
+                did_you_mean,
             ]);
 
             title = VALUE_NOT_EXPOSED;
@@ -1176,8 +1197,6 @@ fn not_found<'b>(
     thing: &'b str,
     options: MutSet<Box<str>>,
 ) -> RocDocBuilder<'b> {
-    use crate::error::r#type::suggest;
-
     let mut suggestions = suggest::sort(
         name.as_inline_str().as_str(),
         options.iter().map(|v| v.as_ref()).collect(),

reporting/tests/test_reporting.rs

@@ -298,17 +298,24 @@ mod test_reporting {
         report_problem_as(
             indoc!(
                 r#"
-                List.foobar 1 2
+                List.isempty 1 2
             "#
             ),
             indoc!(
                 r#"
                 ── NOT EXPOSED ─────────────────────────────────────────────────────────────────
 
-                The List module does not expose a foobar value:
+                The List module does not expose `isempty`:
 
-                1│  List.foobar 1 2
-                    ^^^^^^^^^^^
+                1│  List.isempty 1 2
+                    ^^^^^^^^^^^^
+
+                Did you mean one of these?
+
+                    List.isEmpty
+                    List.set
+                    List.get
+                    List.keepIf
                 "#
             ),
         )
@@ -5624,10 +5631,17 @@ mod test_reporting {
                 r#"
                 ── NOT EXPOSED ─────────────────────────────────────────────────────────────────
 
-                The Num module does not expose a if value:
+                The Num module does not expose `if`:
 
                 1│  Num.if
                     ^^^^^^
+
+                Did you mean one of these?
+
+                    Num.sin
+                    Num.div
+                    Num.abs
+                    Num.neg
             "#
             ),
         )