From de2791fe827258a93a02a5125a1a76e64d14ccda Mon Sep 17 00:00:00 2001
From: rvcas <x@rvcas.dev>
Date: Fri, 28 Jul 2023 17:56:56 -0400
Subject: [PATCH] feat(tipo): add new error for redundant clauses

---
 crates/aiken-lang/src/tipo/error.rs      | 16 ++++++++++++++++
 crates/aiken-lang/src/tipo/exhaustive.rs | 13 ++++++++++---
 crates/aiken-lang/src/tipo/expr.rs       | 14 +++-----------
 3 files changed, 29 insertions(+), 14 deletions(-)

diff --git a/crates/aiken-lang/src/tipo/error.rs b/crates/aiken-lang/src/tipo/error.rs
index 7b199fc4..518a2b14 100644
--- a/crates/aiken-lang/src/tipo/error.rs
+++ b/crates/aiken-lang/src/tipo/error.rs
@@ -540,6 +540,22 @@ Maybe you meant to turn it public using the '{keyword_pub}' keyword?"#
         leaked: Type,
     },
 
+    #[error(
+        "{}\n",
+        format!(
+            "I discovered a '{keyword_when}/{keyword_is}' expression with a redundant clause.",
+            keyword_is = "is".if_supports_color(Stdout, |s| s.purple()),
+            keyword_when = "when".if_supports_color(Stdout, |s| s.purple())
+        )
+    )]
+    #[diagnostic(url("https://aiken-lang.org/language-tour/control-flow#matching"))]
+    #[diagnostic(code("redundant_pattern_match"))]
+    #[diagnostic(help("You can safely remove this clause."))]
+    RedundantMatchClause {
+        #[label]
+        location: Span,
+    },
+
     #[error("I couldn't figure out the type of a record you're trying to access.\n")]
     #[diagnostic(url(
         "https://aiken-lang.org/language-tour/variables-and-constants#type-annotations"
diff --git a/crates/aiken-lang/src/tipo/exhaustive.rs b/crates/aiken-lang/src/tipo/exhaustive.rs
index cedc1c5b..53c29e45 100644
--- a/crates/aiken-lang/src/tipo/exhaustive.rs
+++ b/crates/aiken-lang/src/tipo/exhaustive.rs
@@ -428,7 +428,15 @@ fn simplify(environment: &mut Environment, value: &ast::TypedPattern) -> Result<
 
             Ok(Pattern::Constructor(name.to_string(), alts, args))
         }
-        ast::Pattern::Tuple { .. } => todo!(),
+        ast::Pattern::Tuple { elems, .. } =>  {
+            let mut p = Pattern::Constructor(NIL_NAME.to_string(), list_constructors(), vec![]);
+
+            for hd in elems.iter().rev() {
+                p = Pattern::Constructor(CONS_NAME.to_string(), list_constructors(), vec![simplify(environment, hd)?, p]);
+            }
+
+            Ok(p)
+        },
         ast::Pattern::Var { .. } | ast::Pattern::Discard { .. } => Ok(Pattern::Wildcard),
     }
 }
@@ -452,8 +460,7 @@ pub(crate) fn compute_match_usefulness(
         if matrix.is_useful(&pattern_stack) {
             matrix.push(pattern_stack);
         } else {
-            dbg!(&pattern_stack);
-            todo!("redudant")
+            return Err(Error::RedundantMatchClause { location: unchecked_pattern.location() })
         }
     }
 
diff --git a/crates/aiken-lang/src/tipo/expr.rs b/crates/aiken-lang/src/tipo/expr.rs
index b64f1583..e2046e32 100644
--- a/crates/aiken-lang/src/tipo/expr.rs
+++ b/crates/aiken-lang/src/tipo/expr.rs
@@ -48,7 +48,7 @@ impl<'a, 'b> ExprTyper<'a, 'b> {
         subject: &Type,
         typed_clauses: &[TypedClause],
         _location: Span,
-    ) -> Result<(), Vec<String>> {
+    ) -> Result<(), Error> {
         let _value_typ = collapse_links(Arc::new(subject.clone()));
 
         // Currently guards in exhaustiveness checking are assumed that they can fail,
@@ -66,7 +66,7 @@ impl<'a, 'b> ExprTyper<'a, 'b> {
             }
         }
 
-        let _ = dbg!(compute_match_usefulness(self.environment, &patterns));
+        compute_match_usefulness(self.environment, &patterns)?;
 
         // self.environment
         // .check_exhaustiveness(patterns, value_typ, location)
@@ -1881,15 +1881,7 @@ impl<'a, 'b> ExprTyper<'a, 'b> {
             }
         }
 
-        if let Err(unmatched) =
-            self.check_when_exhaustiveness(&subject_type, &typed_clauses, location)
-        {
-            return Err(Error::NotExhaustivePatternMatch {
-                location,
-                unmatched,
-                is_let: false,
-            });
-        }
+        self.check_when_exhaustiveness(&subject_type, &typed_clauses, location)?;
 
         Ok(TypedExpr::When {
             location,