Merge pull request #362 from aiken-lang/patterns-improvements

Patterns improvements

crates/aiken-lang/src/ast.rs

@@ -717,11 +717,6 @@ pub enum Pattern<Constructor, Type> {
         value: String,
     },
 
-    String {
-        location: Span,
-        value: String,
-    },
-
     /// The creation of a variable.
     /// e.g. `assert [this_is_a_var, .._] = x`
     Var {
@@ -776,7 +771,6 @@ impl<A, B> Pattern<A, B> {
             | Pattern::Var { location, .. }
             | Pattern::List { location, .. }
             | Pattern::Discard { location, .. }
-            | Pattern::String { location, .. }
             | Pattern::Tuple { location, .. }
             // | Pattern::Concatenate { location, .. }
             | Pattern::Constructor { location, .. } => *location,

crates/aiken-lang/src/format.rs

@@ -1454,8 +1454,6 @@ impl<'comments> Formatter<'comments> {
         let doc = match pattern {
             Pattern::Int { value, .. } => value.to_doc(),
 
-            Pattern::String { value, .. } => self.string(value),
-
             Pattern::Var { name, .. } => name.to_doc(),
 
             Pattern::Assign { name, pattern, .. } => {

crates/aiken-lang/src/parser.rs

@@ -1689,12 +1689,6 @@ pub fn pattern_parser() -> impl Parser<Token, ast::UntypedPattern, Error = Parse
                     location: span,
                 }
             }),
-            select! {Token::String {value} => value}.map_with_span(|value, span| {
-                ast::UntypedPattern::String {
-                    location: span,
-                    value,
-                }
-            }),
             select! {Token::Int {value} => value}.map_with_span(|value, span| {
                 ast::UntypedPattern::Int {
                     location: span,

crates/aiken-lang/src/tests/check.rs

@@ -0,0 +1,128 @@
+use crate::{
+    ast::{ModuleKind, TypedModule, UntypedModule},
+    builtins, parser,
+    tipo::error::{Error, Warning},
+    IdGenerator,
+};
+use std::collections::HashMap;
+
+fn parse(source_code: &str) -> UntypedModule {
+    let kind = ModuleKind::Lib;
+    let (ast, _) = parser::module(source_code, kind).expect("Failed to parse module");
+    ast
+}
+
+fn check(ast: UntypedModule) -> Result<TypedModule, (Vec<Warning>, Error)> {
+    let kind = ModuleKind::Lib;
+
+    let id_gen = IdGenerator::new();
+
+    let mut warnings = vec![];
+
+    let mut module_types = HashMap::new();
+    module_types.insert("aiken".to_string(), builtins::prelude(&id_gen));
+    module_types.insert("aiken/builtin".to_string(), builtins::plutus(&id_gen));
+
+    let result = ast.infer(&id_gen, kind, "test/project", &module_types, &mut warnings);
+
+    result.map_err(|e| (warnings, e))
+}
+
+#[test]
+fn list_pattern_1() {
+    let source_code = r#"
+        test foo() {
+          let xs = [1, 2, 3]
+          let [x] = xs
+          x == 1
+        }
+    "#;
+    assert!(matches!(
+        check(parse(source_code)),
+        Err((_, Error::NotExhaustivePatternMatch { .. }))
+    ))
+}
+
+#[test]
+fn list_pattern_2() {
+    let source_code = r#"
+        test foo() {
+          let xs = [1, 2, 3]
+          let x = when xs is {
+            [x] -> x
+          }
+          x == 1
+        }
+    "#;
+    assert!(matches!(
+        check(parse(source_code)),
+        Err((_, Error::NotExhaustivePatternMatch { .. }))
+    ))
+}
+
+#[test]
+fn list_pattern_3() {
+    let source_code = r#"
+        test foo() {
+          let xs = [1, 2, 3]
+          let x = when xs is {
+            [x] -> x
+            [x, ..] -> x
+          }
+          x == 1
+        }
+    "#;
+    assert!(matches!(
+        check(parse(source_code)),
+        Err((_, Error::NotExhaustivePatternMatch { .. }))
+    ))
+}
+
+#[test]
+fn list_pattern_4() {
+    let source_code = r#"
+        test foo() {
+          let xs = [1, 2, 3]
+          let x = when xs is {
+            [] -> 1
+            [x] -> x
+            [x, ..] if x > 10 -> x
+          }
+          x == 1
+        }
+    "#;
+    assert!(matches!(
+        check(parse(source_code)),
+        Err((_, Error::NotExhaustivePatternMatch { .. }))
+    ))
+}
+
+#[test]
+fn list_pattern_5() {
+    let source_code = r#"
+        test foo() {
+          let xs = [1, 2, 3]
+          let x = when xs is {
+            [] -> 1
+            [_, ..] -> 1
+          }
+          x == 1
+        }
+    "#;
+    assert!(check(parse(source_code)).is_ok())
+}
+
+#[test]
+fn list_pattern_6() {
+    let source_code = r#"
+        test foo() {
+          let xs = [1, 2, 3]
+          let x = when xs is {
+            [x, ..] -> 1
+            _ -> 1
+          }
+          x == 1
+        }
+    "#;
+    assert!(check(parse(source_code)).is_ok())
+}

crates/aiken-lang/src/tests/mod.rs

@@ -1,3 +1,4 @@
+mod check;
 mod format;
 mod lexer;
 mod parser;

crates/aiken-lang/src/tipo/environment.rs

@@ -1386,6 +1386,10 @@ impl<'a> Environment<'a> {
                     Some(module.clone())
                 };
 
+                if type_name == "List" && module.is_empty() {
+                    return self.check_list_pattern_exhaustiveness(patterns);
+                }
+
                 if let Ok(constructors) = self.get_constructors_for_type(&m, type_name, location) {
                     let mut unmatched_constructors: HashSet<String> =
                         constructors.iter().cloned().collect();
@@ -1426,6 +1430,75 @@ impl<'a> Environment<'a> {
         }
     }
 
+    pub fn check_list_pattern_exhaustiveness(
+        &mut self,
+        patterns: Vec<Pattern<PatternConstructor, Arc<Type>>>,
+    ) -> Result<(), Vec<String>> {
+        let mut cover_empty = false;
+        let mut cover_tail = false;
+
+        let patterns = patterns.iter().map(|p| match p {
+            Pattern::Assign { pattern, .. } => pattern,
+            _ => p,
+        });
+
+        // TODO: We could also warn on redundant patterns. As soon as we've matched the entire
+        // list, any new pattern is redundant. For example:
+        //
+        // when xs is {
+        //   [] => ...
+        //   [x, ..] => ...
+        //   [y] => ...
+        // }
+        //
+        // That last pattern is actually redundant / unreachable.
+        for p in patterns {
+            match p {
+                Pattern::Var { .. } => {
+                    cover_empty = true;
+                    cover_tail = true;
+                }
+                Pattern::Discard { .. } => {
+                    cover_empty = true;
+                    cover_tail = true;
+                }
+                Pattern::List { elements, tail, .. } => {
+                    if elements.is_empty() {
+                        cover_empty = true;
+                    }
+                    match tail {
+                        None => {}
+                        Some(p) => match **p {
+                            Pattern::Discard { .. } => {
+                                cover_tail = true;
+                            }
+                            Pattern::Var { .. } => {
+                                cover_tail = true;
+                            }
+                            _ => {
+                                unreachable!()
+                            }
+                        },
+                    }
+                }
+                _ => {}
+            }
+        }
+
+        if cover_empty && cover_tail {
+            Ok(())
+        } else {
+            let mut missing = vec![];
+            if !cover_empty {
+                missing.push("[]".to_owned());
+            }
+            if !cover_tail {
+                missing.push("[_, ..]".to_owned());
+            }
+            Err(missing)
+        }
+    }
+
     /// Lookup constructors for type in the current scope.
     ///
     pub fn get_constructors_for_type(

crates/aiken-lang/src/tipo/error.rs

@@ -424,7 +424,7 @@ In this particular instance, the following cases are unmatched:
             .iter()
             .map(|s| format!("─▶ {s}"))
             .collect::<Vec<_>>()
-            .join("")
+            .join("\n")
     ))]
     NotExhaustivePatternMatch {
         #[label("{}", if *is_let { "use when/is" } else { "non-exhaustive" })]
@@ -1247,5 +1247,5 @@ fn format_suggestion(sample: &UntypedExpr) -> String {
             }
         })
         .collect::<Vec<_>>()
-        .join("")
+        .join("\n")
 }

crates/aiken-lang/src/tipo/pattern.rs

@@ -16,7 +16,7 @@ use super::{
 };
 use crate::{
     ast::{CallArg, Pattern, Span, TypedPattern, UntypedMultiPattern, UntypedPattern},
-    builtins::{int, list, string, tuple},
+    builtins::{int, list, tuple},
 };
 
 pub struct PatternTyper<'a, 'b> {
@@ -286,12 +286,6 @@ impl<'a, 'b> PatternTyper<'a, 'b> {
                 Ok(Pattern::Int { location, value })
             }
 
-            Pattern::String { location, value } => {
-                self.environment.unify(tipo, string(), location, false)?;
-
-                Ok(Pattern::String { location, value })
-            }
-
             Pattern::List {
                 location,
                 elements,

crates/aiken-lang/src/uplc.rs

@@ -871,7 +871,6 @@ impl<'a> CodeGenerator<'a> {
 
                 pattern_vec.append(values);
             }
-            Pattern::String { .. } => todo!("String matching in whens not yet implemented"),
             Pattern::Var { name, .. } => {
                 pattern_vec.push(Air::Void {
                     scope: scope.clone(),
@@ -1060,7 +1059,6 @@ impl<'a> CodeGenerator<'a> {
     ) {
         match pattern {
             Pattern::Int { .. } => unreachable!(),
-            Pattern::String { .. } => unreachable!(),
             Pattern::Var { .. } => unreachable!(),
             Pattern::Assign { .. } => todo!("Nested assign not yet implemented"),
             Pattern::Discard { .. } => {
@@ -1536,8 +1534,7 @@ impl<'a> CodeGenerator<'a> {
                 Some(item_name)
             }
             Pattern::Assign { .. } => todo!("Nested assign is not yet done"),
-            Pattern::Int { .. } => unimplemented!(),
-            Pattern::String { .. } => unimplemented!(),
+            Pattern::Int { .. } => todo!("Nested pattern-match on integers isn't implemented yet. Use when clause-guard as an alternative, or break down the pattern."),
         }
     }
 
@@ -1569,7 +1566,7 @@ impl<'a> CodeGenerator<'a> {
             )
         }
         match pattern {
-            Pattern::Int { .. } | Pattern::String { .. } => unreachable!(),
+            Pattern::Int { .. } => unreachable!(),
             Pattern::Var { name, .. } => {
                 pattern_vec.push(Air::Let {
                     name: name.clone(),
@@ -1690,7 +1687,6 @@ impl<'a> CodeGenerator<'a> {
     ) {
         match pattern {
             Pattern::Int { .. } => todo!(),
-            Pattern::String { .. } => todo!(),
             Pattern::Var { .. } => todo!(),
             Pattern::Assign { .. } => todo!(),
             Pattern::Discard { .. } => todo!(),
@@ -1736,7 +1732,6 @@ impl<'a> CodeGenerator<'a> {
                             );
                         }
                         Pattern::Int { .. } => todo!(),
-                        Pattern::String { .. } => todo!(),
                         Pattern::Assign { .. } => todo!(),
                         Pattern::Discard { .. } => {
                             names.push("_".to_string());
@@ -1904,7 +1899,6 @@ impl<'a> CodeGenerator<'a> {
     ) {
         match pattern {
             Pattern::Int { .. } => unreachable!(),
-            Pattern::String { .. } => unreachable!(),
             Pattern::Var { name, .. } => {
                 pattern_vec.append(value_vec);
 
@@ -2651,7 +2645,6 @@ impl<'a> CodeGenerator<'a> {
                     (false, tuple_name)
                 }
                 Pattern::Int { .. } => todo!(),
-                Pattern::String { .. } => todo!(),
                 Pattern::Assign { .. } => todo!(),
             };