Implement type inference for boolean operators

crates/ra_hir/src/ty.rs

@@ -26,7 +26,7 @@ use ena::unify::{InPlaceUnificationTable, UnifyKey, UnifyValue, NoError};
 
 use ra_db::{LocalSyntaxPtr, Cancelable};
 use ra_syntax::{
-    ast::{self, AstNode, LoopBodyOwner, ArgListOwner, PrefixOp},
+    ast::{self, AstNode, LoopBodyOwner, ArgListOwner, PrefixOp, BinOp},
     SyntaxNodeRef
 };
 
@@ -906,7 +906,16 @@ impl<'a, D: HirDatabase> InferenceContext<'a, D> {
                 }
             }
             ast::Expr::RangeExpr(_e) => Ty::Unknown,
-            ast::Expr::BinExpr(_e) => Ty::Unknown,
+            ast::Expr::BinExpr(e) => match e.op() {
+                Some(BinOp::BooleanOr)
+                | Some(BinOp::BooleanAnd)
+                | Some(BinOp::EqualityTest)
+                | Some(BinOp::LesserEqualTest)
+                | Some(BinOp::GreaterEqualTest)
+                | Some(BinOp::LesserTest)
+                | Some(BinOp::GreaterTest) => Ty::Bool,
+                _ => Ty::Unknown,
+            },
             ast::Expr::Literal(_e) => Ty::Unknown,
         };
         // use a new type variable if we got Ty::Unknown here

crates/ra_hir/src/ty/tests.rs

@@ -153,6 +153,23 @@ impl S {
     );
 }
 
+#[test]
+fn infer_boolean_op() {
+    check_inference(
+        r#"
+fn test() {
+    let x = a && b;
+    let y = true || false;
+    let z = x == y;
+    let h = CONST_1 <= CONST_2;
+
+    10 < 3
+}
+"#,
+        "0008_boolean_op.txt",
+    );
+}
+
 fn infer(content: &str) -> String {
     let (db, _, file_id) = MockDatabase::with_single_file(content);
     let source_file = db.source_file(file_id);

crates/ra_hir/src/ty/tests/data/0008_boolean_op.txt

@@ -0,0 +1,10 @@
+[21; 22) 'x': bool
+[68; 69) 'z': bool
+[72; 78) 'x == y': bool
+[45; 58) 'true || false': bool
+[11; 125) '{     ... < 3 }': bool
+[117; 123) '10 < 3': bool
+[88; 89) 'h': bool
+[41; 42) 'y': bool
+[92; 110) 'CONST_...ONST_2': bool
+[25; 31) 'a && b': bool

crates/ra_syntax/src/ast.rs

@@ -488,6 +488,45 @@ impl<'a> PrefixExpr<'a> {
     }
 }
 
+#[derive(Copy, Clone, Debug, PartialEq, Eq, Hash)]
+pub enum BinOp {
+    /// The `||` operator for boolean OR
+    BooleanOr,
+    /// The `&&` operator for boolean AND
+    BooleanAnd,
+    /// The `==` operator for equality testing
+    EqualityTest,
+    /// The `<=` operator for lesser-equal testing
+    LesserEqualTest,
+    /// The `>=` operator for greater-equal testing
+    GreaterEqualTest,
+    /// The `<` operator for comparison
+    LesserTest,
+    /// The `>` operator for comparison
+    GreaterTest,
+    // TODO: lots of others
+}
+
+impl<'a> BinExpr<'a> {
+    pub fn op(&self) -> Option<BinOp> {
+        self.syntax()
+            .children()
+            .filter_map(|c| {
+                match c.kind() {
+                    PIPEPIPE => Some(BinOp::BooleanOr),
+                    AMPAMP => Some(BinOp::BooleanAnd),
+                    EQEQ => Some(BinOp::EqualityTest),
+                    LTEQ => Some(BinOp::LesserEqualTest),
+                    GTEQ => Some(BinOp::GreaterEqualTest),
+                    L_ANGLE => Some(BinOp::LesserTest),
+                    R_ANGLE => Some(BinOp::GreaterTest),
+                    _ => None,
+                }
+            })
+            .next()
+    }
+}
+
 #[derive(Copy, Clone, Debug, PartialEq, Eq, Hash)]
 pub enum SelfParamFlavor {
     /// self

crates/ra_syntax/src/ast/generated.rs

@@ -217,7 +217,15 @@ impl<R: TreeRoot<RaTypes>> BinExprNode<R> {
 }
 
 
-impl<'a> BinExpr<'a> {}
+impl<'a> BinExpr<'a> {
+    pub fn lhs(self) -> Option<Expr<'a>> {
+        super::child_opt(self)
+    }
+
+    pub fn rhs(self) -> Option<Expr<'a>> {
+        super::child_opt(self)
+    }
+}
 
 // BindPat
 #[derive(Debug, Clone, Copy,)]

crates/ra_syntax/src/grammar.ron

@@ -422,7 +422,12 @@ Grammar(
         "RefExpr": (options: ["Expr"]),
         "PrefixExpr": (options: ["Expr"]),
         "RangeExpr": (),
-        "BinExpr": (),
+        "BinExpr": (
+            options: [
+                ["lhs", "Expr"],
+                ["rhs", "Expr"]
+            ]
+        ),
         "String": (),
         "Byte": (),
         "ByteString": (),