Implement type inference for more binary operators

Mostly just for primitive numeric types such as u32 and f64. Not
yet a general solution using trait resolution.

3 files changed, 82 insertions, 47 deletions

diff --git a/crates/ra_hir/src/ty.rs b/crates/ra_hir/src/ty.rs
index 23ee76f4e..e09279a68 100644
--- a/crates/ra_hir/src/ty.rs
+++ b/crates/ra_hir/src/ty.rs
@@ -529,7 +529,7 @@ struct InferenceContext<'a, D: HirDatabase> {
 
 // helper function that determines whether a binary operator
 // always returns a boolean
-fn is_boolean_operator(op: BinaryOp) -> bool {
+fn boolean_op_return_ty(op: BinaryOp, rhs_ty: Ty) -> Ty {
     match op {
         BinaryOp::BooleanOr
         | BinaryOp::BooleanAnd
@@ -537,8 +537,32 @@ fn is_boolean_operator(op: BinaryOp) -> bool {
         | BinaryOp::LesserEqualTest
         | BinaryOp::GreaterEqualTest
         | BinaryOp::LesserTest
-        | BinaryOp::GreaterTest => true,
-        _ => false,
+        | BinaryOp::GreaterTest => Ty::Bool,
+        BinaryOp::Assignment
+        | BinaryOp::AddAssign
+        | BinaryOp::SubAssign
+        | BinaryOp::DivAssign
+        | BinaryOp::MulAssign
+        | BinaryOp::RemAssign
+        | BinaryOp::ShrAssign
+        | BinaryOp::ShlAssign
+        | BinaryOp::BitAndAssign
+        | BinaryOp::BitOrAssign
+        | BinaryOp::BitXorAssign => Ty::unit(),
+        BinaryOp::Addition
+        | BinaryOp::Subtraction
+        | BinaryOp::Multiplication
+        | BinaryOp::Division
+        | BinaryOp::Remainder
+        | BinaryOp::LeftShift
+        | BinaryOp::RightShift
+        | BinaryOp::BitwiseAnd
+        | BinaryOp::BitwiseOr
+        | BinaryOp::BitwiseXor => match rhs_ty {
+            Ty::Uint(..) | Ty::Int(..) | Ty::Float(..) => rhs_ty,
+            _ => Ty::Unknown,
+        },
+        BinaryOp::RangeRightOpen | BinaryOp::RangeRightClosed => Ty::Unknown,
     }
 }
 
@@ -890,20 +914,59 @@ impl<'a, D: HirDatabase> InferenceContext<'a, D> {
             }
             Expr::BinaryOp { lhs, rhs, op } => match op {
                 Some(op) => {
-                    let subtype_expectation = match op {
+                    let lhs_expectation = match op {
                         BinaryOp::BooleanAnd | BinaryOp::BooleanOr => {
                             Expectation::has_type(Ty::Bool)
                         }
                         _ => Expectation::none(),
                     };
-                    let _lhs_ty = self.infer_expr(*lhs, &subtype_expectation)?;
-                    let _rhs_ty = self.infer_expr(*rhs, &subtype_expectation)?;
+                    let lhs_ty = self.infer_expr(*lhs, &lhs_expectation)?;
+                    // TODO: find implementation of trait corresponding to operation
+                    // symbol and resolve associated `Output` type
+                    let rhs_expectation = match op {
+                        BinaryOp::BooleanAnd | BinaryOp::BooleanOr => Ty::Bool,
+                        BinaryOp::Assignment | BinaryOp::EqualityTest => match lhs_ty {
+                            Ty::Uint(..)
+                            | Ty::Int(..)
+                            | Ty::Float(..)
+                            | Ty::Str
+                            | Ty::Char
+                            | Ty::Bool => lhs_ty,
+                            _ => Ty::Unknown,
+                        },
+                        BinaryOp::LesserEqualTest
+                        | BinaryOp::GreaterEqualTest
+                        | BinaryOp::LesserTest
+                        | BinaryOp::GreaterTest
+                        | BinaryOp::AddAssign
+                        | BinaryOp::SubAssign
+                        | BinaryOp::DivAssign
+                        | BinaryOp::MulAssign
+                        | BinaryOp::RemAssign
+                        | BinaryOp::ShrAssign
+                        | BinaryOp::ShlAssign
+                        | BinaryOp::BitAndAssign
+                        | BinaryOp::BitOrAssign
+                        | BinaryOp::BitXorAssign
+                        | BinaryOp::Addition
+                        | BinaryOp::Subtraction
+                        | BinaryOp::Multiplication
+                        | BinaryOp::Division
+                        | BinaryOp::Remainder
+                        | BinaryOp::LeftShift
+                        | BinaryOp::RightShift
+                        | BinaryOp::BitwiseAnd
+                        | BinaryOp::BitwiseOr
+                        | BinaryOp::BitwiseXor => match lhs_ty {
+                            Ty::Uint(..) | Ty::Int(..) | Ty::Float(..) => lhs_ty,
+                            _ => Ty::Unknown,
+                        },
+                        _ => Ty::Unknown,
+                    };
+                    let rhs_ty = self.infer_expr(*rhs, &Expectation::has_type(rhs_expectation))?;
 
-                    if is_boolean_operator(*op) {
-                        Ty::Bool
-                    } else {
-                        Ty::Unknown
-                    }
+                    // TODO: similar as above, return ty is often associated trait type
+                    boolean_op_return_ty(*op, rhs_ty)
                 }
                 _ => Ty::Unknown,
             },
diff --git a/crates/ra_hir/src/ty/tests.rs b/crates/ra_hir/src/ty/tests.rs
index e6c7e225b..2749d740c 100644
--- a/crates/ra_hir/src/ty/tests.rs
+++ b/crates/ra_hir/src/ty/tests.rs
@@ -157,7 +157,7 @@ impl S {
 }
 
 #[test]
-fn infer_boolean_op() {
+fn infer_binary_op() {
     check_inference(
         r#"
 fn f(x: bool) -> i32 {
@@ -168,15 +168,18 @@ fn test() {
     let x = a && b;
     let y = true || false;
     let z = x == y;
-    let h = CONST_1 <= CONST_2;
+    let minus_forty: isize = -40isize;
+    let h = minus_forty <= CONST_2;
     let c = f(z || y) + 5;
     let d = b;
-    let e = 3i32 && "hello world";
+    let g = minus_forty ^= i;
+    let ten: usize = 10;
+    let ten_is_eleven = ten == some_num;
 
-    10 < 3
+    ten < 3
 }
 "#,
-        "boolean_op.txt",
+        "binary_op.txt",
     );
 }
 
diff --git a/crates/ra_hir/src/ty/tests/data/boolean_op.txt b/crates/ra_hir/src/ty/tests/data/boolean_op.txt
deleted file mode 100644
index cce8d68fb..000000000
--- a/crates/ra_hir/src/ty/tests/data/boolean_op.txt
+++ /dev/null
@@ -1,31 +0,0 @@
-[6; 7) 'x': [unknown]
-[22; 34) '{     0i32 }': i32
-[28; 32) '0i32': i32
-[46; 237) '{     ... < 3 }': bool
-[56; 57) 'x': bool
-[60; 61) 'a': bool
-[60; 66) 'a && b': bool
-[65; 66) 'b': bool
-[76; 77) 'y': bool
-[80; 84) 'true': bool
-[80; 93) 'true || false': bool
-[88; 93) 'false': bool
-[103; 104) 'z': bool
-[107; 108) 'x': bool
-[107; 113) 'x == y': bool
-[112; 113) 'y': bool
-[123; 124) 'h': bool
-[127; 134) 'CONST_1': [unknown]
-[127; 145) 'CONST_...ONST_2': bool
-[138; 145) 'CONST_2': [unknown]
-[155; 156) 'c': [unknown]
-[159; 172) 'f(z || y) + 5': [unknown]
-[182; 183) 'd': [unknown]
-[186; 187) 'b': [unknown]
-[197; 198) 'e': bool
-[201; 205) '3i32': bool
-[201; 222) '3i32 &...world"': bool
-[209; 222) '"hello world"': bool
-[229; 231) '10': [unknown]
-[229; 235) '10 < 3': bool
-[234; 235) '3': [unknown]