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-rw-r--r--crates/ra_hir_ty/src/infer.rs41
-rw-r--r--crates/ra_hir_ty/src/infer/expr.rs8
-rw-r--r--crates/ra_hir_ty/src/tests/coercion.rs31
3 files changed, 71 insertions, 9 deletions
diff --git a/crates/ra_hir_ty/src/infer.rs b/crates/ra_hir_ty/src/infer.rs
index 6e1d268de..569d46cc3 100644
--- a/crates/ra_hir_ty/src/infer.rs
+++ b/crates/ra_hir_ty/src/infer.rs
@@ -583,21 +583,52 @@ impl InferTy {
583#[derive(Clone, PartialEq, Eq, Debug)] 583#[derive(Clone, PartialEq, Eq, Debug)]
584struct Expectation { 584struct Expectation {
585 ty: Ty, 585 ty: Ty,
586 // FIXME: In some cases, we need to be aware whether the expectation is that 586 /// See the `rvalue_hint` method.
587 // the type match exactly what we passed, or whether it just needs to be 587 rvalue_hint: bool,
588 // coercible to the expected type. See Expectation::rvalue_hint in rustc.
589} 588}
590 589
591impl Expectation { 590impl Expectation {
592 /// The expectation that the type of the expression needs to equal the given 591 /// The expectation that the type of the expression needs to equal the given
593 /// type. 592 /// type.
594 fn has_type(ty: Ty) -> Self { 593 fn has_type(ty: Ty) -> Self {
595 Expectation { ty } 594 Expectation { ty, rvalue_hint: false }
595 }
596
597 /// The following explanation is copied straight from rustc:
598 /// Provides an expectation for an rvalue expression given an *optional*
599 /// hint, which is not required for type safety (the resulting type might
600 /// be checked higher up, as is the case with `&expr` and `box expr`), but
601 /// is useful in determining the concrete type.
602 ///
603 /// The primary use case is where the expected type is a fat pointer,
604 /// like `&[isize]`. For example, consider the following statement:
605 ///
606 /// let x: &[isize] = &[1, 2, 3];
607 ///
608 /// In this case, the expected type for the `&[1, 2, 3]` expression is
609 /// `&[isize]`. If however we were to say that `[1, 2, 3]` has the
610 /// expectation `ExpectHasType([isize])`, that would be too strong --
611 /// `[1, 2, 3]` does not have the type `[isize]` but rather `[isize; 3]`.
612 /// It is only the `&[1, 2, 3]` expression as a whole that can be coerced
613 /// to the type `&[isize]`. Therefore, we propagate this more limited hint,
614 /// which still is useful, because it informs integer literals and the like.
615 /// See the test case `test/ui/coerce-expect-unsized.rs` and #20169
616 /// for examples of where this comes up,.
617 fn rvalue_hint(ty: Ty) -> Self {
618 Expectation { ty, rvalue_hint: true }
596 } 619 }
597 620
598 /// This expresses no expectation on the type. 621 /// This expresses no expectation on the type.
599 fn none() -> Self { 622 fn none() -> Self {
600 Expectation { ty: Ty::Unknown } 623 Expectation { ty: Ty::Unknown, rvalue_hint: false }
624 }
625
626 fn coercion_target(&self) -> &Ty {
627 if self.rvalue_hint {
628 &Ty::Unknown
629 } else {
630 &self.ty
631 }
601 } 632 }
602} 633}
603 634
diff --git a/crates/ra_hir_ty/src/infer/expr.rs b/crates/ra_hir_ty/src/infer/expr.rs
index 9d5f75625..3db5b2b51 100644
--- a/crates/ra_hir_ty/src/infer/expr.rs
+++ b/crates/ra_hir_ty/src/infer/expr.rs
@@ -42,14 +42,14 @@ impl<'a, D: HirDatabase> InferenceContext<'a, D> {
42 /// Return the type after possible coercion. 42 /// Return the type after possible coercion.
43 pub(super) fn infer_expr_coerce(&mut self, expr: ExprId, expected: &Expectation) -> Ty { 43 pub(super) fn infer_expr_coerce(&mut self, expr: ExprId, expected: &Expectation) -> Ty {
44 let ty = self.infer_expr_inner(expr, &expected); 44 let ty = self.infer_expr_inner(expr, &expected);
45 let ty = if !self.coerce(&ty, &expected.ty) { 45 let ty = if !self.coerce(&ty, &expected.coercion_target()) {
46 self.result 46 self.result
47 .type_mismatches 47 .type_mismatches
48 .insert(expr, TypeMismatch { expected: expected.ty.clone(), actual: ty.clone() }); 48 .insert(expr, TypeMismatch { expected: expected.ty.clone(), actual: ty.clone() });
49 // Return actual type when type mismatch. 49 // Return actual type when type mismatch.
50 // This is needed for diagnostic when return type mismatch. 50 // This is needed for diagnostic when return type mismatch.
51 ty 51 ty
52 } else if expected.ty == Ty::Unknown { 52 } else if expected.coercion_target() == &Ty::Unknown {
53 ty 53 ty
54 } else { 54 } else {
55 expected.ty.clone() 55 expected.ty.clone()
@@ -297,7 +297,7 @@ impl<'a, D: HirDatabase> InferenceContext<'a, D> {
297 // FIXME: throw type error - expected mut reference but found shared ref, 297 // FIXME: throw type error - expected mut reference but found shared ref,
298 // which cannot be coerced 298 // which cannot be coerced
299 } 299 }
300 Expectation::has_type(Ty::clone(exp_inner)) 300 Expectation::rvalue_hint(Ty::clone(exp_inner))
301 } else { 301 } else {
302 Expectation::none() 302 Expectation::none()
303 }; 303 };
@@ -542,7 +542,7 @@ impl<'a, D: HirDatabase> InferenceContext<'a, D> {
542 let ty = if let Some(expr) = tail { 542 let ty = if let Some(expr) = tail {
543 self.infer_expr_coerce(expr, expected) 543 self.infer_expr_coerce(expr, expected)
544 } else { 544 } else {
545 self.coerce(&Ty::unit(), &expected.ty); 545 self.coerce(&Ty::unit(), expected.coercion_target());
546 Ty::unit() 546 Ty::unit()
547 }; 547 };
548 if diverges { 548 if diverges {
diff --git a/crates/ra_hir_ty/src/tests/coercion.rs b/crates/ra_hir_ty/src/tests/coercion.rs
index 60ad6e9be..1e303f5ce 100644
--- a/crates/ra_hir_ty/src/tests/coercion.rs
+++ b/crates/ra_hir_ty/src/tests/coercion.rs
@@ -458,6 +458,37 @@ fn test() {
458} 458}
459 459
460#[test] 460#[test]
461fn coerce_autoderef_block() {
462 assert_snapshot!(
463 infer_with_mismatches(r#"
464struct String {}
465#[lang = "deref"]
466trait Deref { type Target; }
467impl Deref for String { type Target = str; }
468fn takes_ref_str(x: &str) {}
469fn returns_string() -> String { loop {} }
470fn test() {
471 takes_ref_str(&{ returns_string() });
472}
473"#, true),
474 @r###"
475 [127; 128) 'x': &str
476 [136; 138) '{}': ()
477 [169; 180) '{ loop {} }': String
478 [171; 178) 'loop {}': !
479 [176; 178) '{}': ()
480 [191; 236) '{ ... }); }': ()
481 [197; 210) 'takes_ref_str': fn takes_ref_str(&str) -> ()
482 [197; 233) 'takes_...g() })': ()
483 [211; 232) '&{ ret...ng() }': &String
484 [212; 232) '{ retu...ng() }': String
485 [214; 228) 'returns_string': fn returns_string() -> String
486 [214; 230) 'return...ring()': String
487 "###
488 );
489}
490
491#[test]
461fn closure_return_coerce() { 492fn closure_return_coerce() {
462 assert_snapshot!( 493 assert_snapshot!(
463 infer_with_mismatches(r#" 494 infer_with_mismatches(r#"