[lang] Type checking support for if-let syntax (#1095)

crates/samlang-core/src/ast/source.rs

@@ -219,7 +219,7 @@ pub(crate) mod pattern {
   pub(crate) enum DestructuringPattern<T: Clone> {
     Tuple(Location, Vec<TuplePatternElement<DestructuringPattern<T>, T>>),
     Object(Location, Vec<ObjectPatternElement<DestructuringPattern<T>, T>>),
-    Id(Id),
+    Id(Id, T),
     Wildcard(Location),
   }
 
@@ -228,7 +228,7 @@ pub(crate) mod pattern {
       match self {
         Self::Tuple(loc, _)
         | Self::Object(loc, _)
-        | Self::Id(Id { loc, .. })
+        | Self::Id(Id { loc, .. }, _)
         | Self::Wildcard(loc) => loc,
       }
     }
@@ -239,16 +239,16 @@ pub(crate) mod pattern {
     pub(crate) loc: Location,
     pub(crate) tag_order: usize,
     pub(crate) tag: Id,
-    pub(crate) data_variables: Vec<MatchingPattern<T>>,
+    pub(crate) data_variables: Vec<(MatchingPattern<T>, T)>,
     pub(crate) type_: T,
   }
 
   #[derive(Clone, PartialEq, Eq)]
   pub(crate) enum MatchingPattern<T: Clone> {
-    Tuple(Location, Vec<TuplePatternElement<DestructuringPattern<T>, T>>),
-    Object(Location, Vec<ObjectPatternElement<DestructuringPattern<T>, T>>),
+    Tuple(Location, Vec<TuplePatternElement<MatchingPattern<T>, T>>),
+    Object(Location, Vec<ObjectPatternElement<MatchingPattern<T>, T>>),
     Variant(VariantPattern<T>),
-    Id(Id),
+    Id(Id, T),
     Wildcard(Location),
   }
 
@@ -258,7 +258,7 @@ pub(crate) mod pattern {
         Self::Tuple(loc, _)
         | Self::Object(loc, _)
         | Self::Variant(VariantPattern { loc, .. })
-        | Self::Id(Id { loc, .. })
+        | Self::Id(Id { loc, .. }, _)
         | Self::Wildcard(loc) => loc,
       }
     }
@@ -424,10 +424,16 @@ pub(crate) mod expr {
     pub(crate) e2: Box<E<T>>,
   }
 
+  #[derive(Clone, PartialEq, Eq)]
+  pub(crate) enum IfElseCondition<T: Clone> {
+    Expression(E<T>),
+    Guard(super::pattern::MatchingPattern<T>, E<T>),
+  }
+
   #[derive(Clone, PartialEq, Eq)]
   pub(crate) struct IfElse<T: Clone> {
     pub(crate) common: ExpressionCommon<T>,
-    pub(crate) condition: Box<E<T>>,
+    pub(crate) condition: Box<IfElseCondition<T>>,
     pub(crate) e1: Box<E<T>>,
     pub(crate) e2: Box<E<T>>,
   }

crates/samlang-core/src/ast/source_tests.rs

@@ -45,7 +45,7 @@ mod tests {
     assert_eq!(*destructuring_pattern.loc(), Location::dummy());
     destructuring_pattern = pattern::DestructuringPattern::Tuple(Location::dummy(), vec![]);
     assert_eq!(*destructuring_pattern.loc(), Location::dummy());
-    destructuring_pattern = pattern::DestructuringPattern::Id(Id::from(PStr::LOWER_A));
+    destructuring_pattern = pattern::DestructuringPattern::Id(Id::from(PStr::LOWER_A), ());
     assert_eq!(*destructuring_pattern.loc(), Location::dummy());
     destructuring_pattern = pattern::DestructuringPattern::Wildcard(Location::dummy());
     assert_eq!(*destructuring_pattern.loc(), Location::dummy());
@@ -63,7 +63,7 @@ mod tests {
       type_: (),
     });
     assert_eq!(*matching_pattern.clone().loc(), Location::dummy());
-    matching_pattern = pattern::MatchingPattern::Id(Id::from(PStr::LOWER_A));
+    matching_pattern = pattern::MatchingPattern::Id(Id::from(PStr::LOWER_A), ());
     assert_eq!(*matching_pattern.loc(), Location::dummy());
     matching_pattern = pattern::MatchingPattern::Wildcard(Location::dummy());
     assert_eq!(*matching_pattern.loc(), Location::dummy());
@@ -205,7 +205,16 @@ mod tests {
     }));
     coverage_hack_for_expr(E::IfElse(IfElse {
       common: common.clone(),
-      condition: Box::new(zero_expr.clone()),
+      condition: Box::new(IfElseCondition::Expression(zero_expr.clone())),
+      e1: Box::new(zero_expr.clone()),
+      e2: Box::new(zero_expr.clone()),
+    }));
+    coverage_hack_for_expr(E::IfElse(IfElse {
+      common: common.clone(),
+      condition: Box::new(IfElseCondition::Guard(
+        pattern::MatchingPattern::Wildcard(Location::dummy()),
+        zero_expr.clone(),
+      )),
       e1: Box::new(zero_expr.clone()),
       e2: Box::new(zero_expr.clone()),
     }));
@@ -242,9 +251,10 @@ mod tests {
               loc: Location::dummy(),
               field_order: 0,
               field_name: Id::from(heap.alloc_str_for_test("name")),
-              pattern: Box::new(pattern::DestructuringPattern::Id(Id::from(
-                heap.alloc_str_for_test("name"),
-              ))),
+              pattern: Box::new(pattern::DestructuringPattern::Id(
+                Id::from(heap.alloc_str_for_test("name")),
+                (),
+              )),
               shorthand: true,
               type_: (),
             }],
@@ -262,9 +272,10 @@ mod tests {
           pattern: pattern::DestructuringPattern::Tuple(
             Location::dummy(),
             vec![pattern::TuplePatternElement {
-              pattern: Box::new(pattern::DestructuringPattern::Id(Id::from(
-                heap.alloc_str_for_test("name"),
-              ))),
+              pattern: Box::new(pattern::DestructuringPattern::Id(
+                Id::from(heap.alloc_str_for_test("name")),
+                (),
+              )),
               type_: (),
             }],
           ),
@@ -289,7 +300,7 @@ mod tests {
         expr::DeclarationStatement {
           loc: Location::dummy(),
           associated_comments: NO_COMMENT_REFERENCE,
-          pattern: pattern::DestructuringPattern::Id(Id::from(heap.alloc_str_for_test("s"))),
+          pattern: pattern::DestructuringPattern::Id(Id::from(heap.alloc_str_for_test("s")), ()),
           annotation: Some(annotation::T::Fn(annotation::Function {
             location: Location::dummy(),
             associated_comments: NO_COMMENT_REFERENCE,

crates/samlang-core/src/checker/checker_tests.rs

@@ -2586,11 +2586,21 @@ Found 1 error.
       "{ let _ = (b: bool, t: int, f: int) -> if b then t else f; }",
       &builder.unit_type(),
     );
+    assert_checks(
+      heap,
+      "{ let _ = (t: Test) -> if let {foo, bar as _} = t then 1 else 2; }",
+      &builder.unit_type(),
+    );
     assert_checks(
       heap,
       "{ let _ = (t: Test2) -> match (t) { Foo(_) -> 1, Bar(s) -> 2 }; }",
       &builder.unit_type(),
     );
+    assert_checks(
+      heap,
+      "{ let _ = (t: Test2) -> if let Foo(_) = t then 1 else 2; }",
+      &builder.unit_type(),
+    );
     assert_errors_full_customization(
       heap,
       "{ let _ = (t: Test2) -> match (t) { Foo(_) -> 1, Bar(s) -> 2 }; }",
@@ -2716,6 +2726,79 @@ Error ---------------------------------- DUMMY.sam:3:22-3:23
 Found 1 error.
 "#,
     );
+    assert_errors_full_customization(
+      heap,
+      "{ let _ = (t: Test) -> if let [a, b, _] = [1, 2] then 1 else 2; }",
+      &builder.unit_type(),
+      r#"
+Error ---------------------------------- DUMMY.sam:1:38-1:39
+
+Cannot access member of `Pair<int, int>` at index 2.
+
+  1| { let _ = (t: Test) -> if let [a, b, _] = [1, 2] then 1 else 2; }
+                                          ^
+
+
+Found 1 error.
+"#,
+      "Test",
+      true,
+    );
+    assert_errors_full_customization(
+      heap,
+      r#"{ let _ = (t: Test) -> if let {bar, boo} = t then 1 else 2;
+let _ = (t: Test) -> if let [_, bar] = t then 1 else 2;
+let _ = (t: Test2) -> if let Foo(_) = t then 1 else 2;
+let _ = (t: Test2) -> if let Foo(_, _) = t then 1 else 2;
+let _ = (t: Test2) -> if let Foo111(_) = t then 1 else 2;
+}"#,
+      &builder.unit_type(),
+      r#"
+Error ---------------------------------- DUMMY.sam:1:32-1:35
+
+Cannot find member `bar` on `Test`.
+
+  1| { let _ = (t: Test) -> if let {bar, boo} = t then 1 else 2;
+                                    ^^^
+
+
+Error ---------------------------------- DUMMY.sam:1:37-1:40
+
+Cannot find member `boo` on `Test`.
+
+  1| { let _ = (t: Test) -> if let {bar, boo} = t then 1 else 2;
+                                         ^^^
+
+
+Error ---------------------------------- DUMMY.sam:2:33-2:36
+
+Cannot access member of `Test` at index 1.
+
+  2| let _ = (t: Test) -> if let [_, bar] = t then 1 else 2;
+                                     ^^^
+
+
+Error ---------------------------------- DUMMY.sam:4:37-4:38
+
+Cannot access member of `Test2` at index 1.
+
+  4| let _ = (t: Test2) -> if let Foo(_, _) = t then 1 else 2;
+                                         ^
+
+
+Error ---------------------------------- DUMMY.sam:5:30-5:36
+
+Cannot find member `Foo111` on `Test2`.
+
+  5| let _ = (t: Test2) -> if let Foo111(_) = t then 1 else 2;
+                                  ^^^^^^
+
+
+Found 5 errors.
+"#,
+      "Test2",
+      false,
+    );
     assert_errors(
       heap,
       "match (3) { Foo(_) -> 1, Bar(s) -> 2 }",