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Auto merge of #57230 - estebank:return-mismatch, r=varkor 

Modify mismatched type error for functions with no return

Fix #50009.

```
error[E0308]: mismatched types
  --> $DIR/coercion-missing-tail-expected-type.rs:3:24
   |
LL | fn plus_one(x: i32) -> i32 { //~ ERROR mismatched types
   |    --------            ^^^ expected i32, found ()
   |    |
   |    this function's body doesn't return
LL |     x + 1;
   |          - help: consider removing this semicolon
   |
   = note: expected type `i32`
              found type `()`
```

instead of

```
error[E0308]: mismatched types
  --> $DIR/coercion-missing-tail-expected-type.rs:3:28
   |
LL |   fn plus_one(x: i32) -> i32 { //~ ERROR mismatched types
   |  ____________________________^
LL | |     x + 1;
   | |          - help: consider removing this semicolon
LL | | }
   | |_^ expected i32, found ()
   |
   = note: expected type `i32`
              found type `()`
```
This commit is contained in:
bors 2019-01-05 22:25:47 +00:00
parent 68fe5182c9 211365d68c
commit ad9068f874
14 changed files with 201 additions and 158 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

3
src/librustc/hir/map/mod.rs
View File

@ -667,6 +667,7 @@ impl<'hir> Map<'hir> {
Node::Item(_) |
Node::ForeignItem(_) |
Node::TraitItem(_) |
Node::Expr(Expr { node: ExprKind::Closure(..), ..}) |
Node::ImplItem(_) => true,
_ => false,
}
@ -675,7 +676,7 @@ impl<'hir> Map<'hir> {
match *node {
Node::Expr(ref expr) => {
match expr.node {
ExprKind::While(..) | ExprKind::Loop(..) => true,
ExprKind::While(..) | ExprKind::Loop(..) | ExprKind::Ret(..) => true,
_ => false,
}
}

132
src/librustc_typeck/check/mod.rs
View File

@ -4843,11 +4843,31 @@ impl<'a, 'gcx, 'tcx> FnCtxt<'a, 'gcx, 'tcx> {
// #41425 -- label the implicit `()` as being the
// "found type" here, rather than the "expected type".
if !self.diverges.get().always() {
coerce.coerce_forced_unit(self, &self.misc(blk.span), &mut |err| {
// #50009 -- Do not point at the entire fn block span, point at the return type
// span, as it is the cause of the requirement, and
// `consider_hint_about_removing_semicolon` will point at the last expression
// if it were a relevant part of the error. This improves usability in editors
// that highlight errors inline.
let mut sp = blk.span;
let mut fn_span = None;
if let Some((decl, ident)) = self.get_parent_fn_decl(blk.id) {
let ret_sp = decl.output.span();
if let Some(block_sp) = self.parent_item_span(blk.id) {
// HACK: on some cases (`ui/liveness/liveness-issue-2163.rs`) the
// output would otherwise be incorrect and even misleading. Make sure
// the span we're aiming at correspond to a `fn` body.
if block_sp == blk.span {
sp = ret_sp;
fn_span = Some(ident.span);
}
}
}
coerce.coerce_forced_unit(self, &self.misc(sp), &mut |err| {
if let Some(expected_ty) = expected.only_has_type(self) {
self.consider_hint_about_removing_semicolon(blk,
expected_ty,
err);
self.consider_hint_about_removing_semicolon(blk, expected_ty, err);
}
if let Some(fn_span) = fn_span {
err.span_label(fn_span, "this function's body doesn't return");
}
}, false);
}
@ -4872,45 +4892,65 @@ impl<'a, 'gcx, 'tcx> FnCtxt<'a, 'gcx, 'tcx> {
ty
}
fn parent_item_span(&self, id: ast::NodeId) -> Option<Span> {
let node = self.tcx.hir().get(self.tcx.hir().get_parent(id));
match node {
Node::Item(&hir::Item {
node: hir::ItemKind::Fn(_, _, _, body_id), ..
}) |
Node::ImplItem(&hir::ImplItem {
node: hir::ImplItemKind::Method(_, body_id), ..
}) => {
let body = self.tcx.hir().body(body_id);
if let ExprKind::Block(block, _) = &body.value.node {
return Some(block.span);
}
}
_ => {}
}
None
}
/// Given a function block's `NodeId`, return its `FnDecl` if it exists, or `None` otherwise.
fn get_parent_fn_decl(&self, blk_id: ast::NodeId) -> Option<(hir::FnDecl, ast::Ident)> {
let parent = self.tcx.hir().get(self.tcx.hir().get_parent(blk_id));
self.get_node_fn_decl(parent).map(|(fn_decl, ident, _)| (fn_decl, ident))
}
/// Given a function `Node`, return its `FnDecl` if it exists, or `None` otherwise.
fn get_node_fn_decl(&self, node: Node) -> Option<(hir::FnDecl, ast::Ident, bool)> {
match node {
Node::Item(&hir::Item {
ident, node: hir::ItemKind::Fn(ref decl, ..), ..
}) => decl.clone().and_then(|decl| {
// This is less than ideal, it will not suggest a return type span on any
// method called `main`, regardless of whether it is actually the entry point,
// but it will still present it as the reason for the expected type.
Some((decl, ident, ident.name != Symbol::intern("main")))
}),
Node::TraitItem(&hir::TraitItem {
ident, node: hir::TraitItemKind::Method(hir::MethodSig {
ref decl, ..
}, ..), ..
}) => decl.clone().and_then(|decl| Some((decl, ident, true))),
Node::ImplItem(&hir::ImplItem {
ident, node: hir::ImplItemKind::Method(hir::MethodSig {
ref decl, ..
}, ..), ..
}) => decl.clone().and_then(|decl| Some((decl, ident, false))),
_ => None,
}
}
/// Given a `NodeId`, return the `FnDecl` of the method it is enclosed by and whether a
/// suggestion can be made, `None` otherwise.
pub fn get_fn_decl(&self, blk_id: ast::NodeId) -> Option<(hir::FnDecl, bool)> {
// Get enclosing Fn, if it is a function or a trait method, unless there's a `loop` or
// `while` before reaching it, as block tail returns are not available in them.
if let Some(fn_id) = self.tcx.hir().get_return_block(blk_id) {
let parent = self.tcx.hir().get(fn_id);
if let Node::Item(&hir::Item {
ident, node: hir::ItemKind::Fn(ref decl, ..), ..
}) = parent {
decl.clone().and_then(|decl| {
// This is less than ideal, it will not suggest a return type span on any
// method called `main`, regardless of whether it is actually the entry point,
// but it will still present it as the reason for the expected type.
Some((decl, ident.name != Symbol::intern("main")))
})
} else if let Node::TraitItem(&hir::TraitItem {
node: hir::TraitItemKind::Method(hir::MethodSig {
ref decl, ..
}, ..), ..
}) = parent {
decl.clone().and_then(|decl| {
Some((decl, true))
})
} else if let Node::ImplItem(&hir::ImplItem {
node: hir::ImplItemKind::Method(hir::MethodSig {
ref decl, ..
}, ..), ..
}) = parent {
decl.clone().and_then(|decl| {
Some((decl, false))
})
} else {
None
}
} else {
None
}
self.tcx.hir().get_return_block(blk_id).and_then(|blk_id| {
let parent = self.tcx.hir().get(blk_id);
self.get_node_fn_decl(parent).map(|(fn_decl, _, is_main)| (fn_decl, is_main))
})
}
/// On implicit return expressions with mismatched types, provide the following suggestions:
@ -4918,13 +4958,15 @@ impl<'a, 'gcx, 'tcx> FnCtxt<'a, 'gcx, 'tcx> {
/// - Point out the method's return type as the reason for the expected type
/// - Possible missing semicolon
/// - Possible missing return type if the return type is the default, and not `fn main()`
pub fn suggest_mismatched_types_on_tail(&self,
err: &mut DiagnosticBuilder<'tcx>,
expression: &'gcx hir::Expr,
expected: Ty<'tcx>,
found: Ty<'tcx>,
cause_span: Span,
blk_id: ast::NodeId) {
pub fn suggest_mismatched_types_on_tail(
&self,
err: &mut DiagnosticBuilder<'tcx>,
expression: &'gcx hir::Expr,
expected: Ty<'tcx>,
found: Ty<'tcx>,
cause_span: Span,
blk_id: ast::NodeId,
) {
self.suggest_missing_semicolon(err, expression, expected, cause_span);
if let Some((fn_decl, can_suggest)) = self.get_fn_decl(blk_id) {
self.suggest_missing_return_type(err, &fn_decl, expected, found, can_suggest);

32
src/test/ui/block-result/consider-removing-last-semi.stderr
View File

@ -1,27 +1,27 @@
error[E0308]: mismatched types
--> $DIR/consider-removing-last-semi.rs:1:18
--> $DIR/consider-removing-last-semi.rs:1:11
|
LL | fn f() -> String { //~ ERROR mismatched types
| __________________^
LL | | 0u8;
LL | | "bla".to_string();
| | - help: consider removing this semicolon
LL | | }
| |_^ expected struct `std::string::String`, found ()
LL | fn f() -> String { //~ ERROR mismatched types
| - ^^^^^^ expected struct `std::string::String`, found ()
| |
| this function's body doesn't return
LL | 0u8;
LL | "bla".to_string();
| - help: consider removing this semicolon
|
= note: expected type `std::string::String`
found type `()`
error[E0308]: mismatched types
--> $DIR/consider-removing-last-semi.rs:6:18
--> $DIR/consider-removing-last-semi.rs:6:11
|
LL | fn g() -> String { //~ ERROR mismatched types
| __________________^
LL | | "this won't work".to_string();
LL | | "removeme".to_string();
| | - help: consider removing this semicolon
LL | | }
| |_^ expected struct `std::string::String`, found ()
LL | fn g() -> String { //~ ERROR mismatched types
| - ^^^^^^ expected struct `std::string::String`, found ()
| |
| this function's body doesn't return
LL | "this won't work".to_string();
LL | "removeme".to_string();
| - help: consider removing this semicolon
|
= note: expected type `std::string::String`
found type `()`

17
src/test/ui/block-result/issue-11714.stderr
View File

@ -1,14 +1,13 @@
error[E0308]: mismatched types
--> $DIR/issue-11714.rs:1:18
--> $DIR/issue-11714.rs:1:14
|
LL | fn blah() -> i32 { //~ ERROR mismatched types
| __________________^
LL | | 1
LL | |
LL | | ;
| | - help: consider removing this semicolon
LL | | }
| |_^ expected i32, found ()
LL | fn blah() -> i32 { //~ ERROR mismatched types
| ---- ^^^ expected i32, found ()
| |
| this function's body doesn't return
...
LL | ;
| - help: consider removing this semicolon
|
= note: expected type `i32`
found type `()`

35
src/test/ui/block-result/issue-13428.stderr
View File

@ -1,30 +1,27 @@
error[E0308]: mismatched types
--> $DIR/issue-13428.rs:3:20
--> $DIR/issue-13428.rs:3:13
|
LL | fn foo() -> String { //~ ERROR mismatched types
| ____________________^
LL | | format!("Hello {}",
LL | | "world")
LL | | // Put the trailing semicolon on its own line to test that the
LL | | // note message gets the offending semicolon exactly
LL | | ;
| | - help: consider removing this semicolon
LL | | }
| |_^ expected struct `std::string::String`, found ()
LL | fn foo() -> String { //~ ERROR mismatched types
| --- ^^^^^^ expected struct `std::string::String`, found ()
| |
| this function's body doesn't return
...
LL | ;
| - help: consider removing this semicolon
|
= note: expected type `std::string::String`
found type `()`
error[E0308]: mismatched types
--> $DIR/issue-13428.rs:11:20
--> $DIR/issue-13428.rs:11:13
|
LL | fn bar() -> String { //~ ERROR mismatched types
| ____________________^
LL | | "foobar".to_string()
LL | | ;
| | - help: consider removing this semicolon
LL | | }
| |_^ expected struct `std::string::String`, found ()
LL | fn bar() -> String { //~ ERROR mismatched types
| --- ^^^^^^ expected struct `std::string::String`, found ()
| |
| this function's body doesn't return
LL | "foobar".to_string()
LL | ;
| - help: consider removing this semicolon
|
= note: expected type `std::string::String`
found type `()`

28
src/test/ui/coercion/coercion-missing-tail-expected-type.stderr
View File

@ -1,25 +1,25 @@
error[E0308]: mismatched types
--> $DIR/coercion-missing-tail-expected-type.rs:3:28
--> $DIR/coercion-missing-tail-expected-type.rs:3:24
|
LL | fn plus_one(x: i32) -> i32 { //~ ERROR mismatched types
| ____________________________^
LL | | x + 1;
| | - help: consider removing this semicolon
LL | | }
| |_^ expected i32, found ()
LL | fn plus_one(x: i32) -> i32 { //~ ERROR mismatched types
| -------- ^^^ expected i32, found ()
| |
| this function's body doesn't return
LL | x + 1;
| - help: consider removing this semicolon
|
= note: expected type `i32`
found type `()`
error[E0308]: mismatched types
--> $DIR/coercion-missing-tail-expected-type.rs:7:29
--> $DIR/coercion-missing-tail-expected-type.rs:7:13
|
LL | fn foo() -> Result<u8, u64> { //~ ERROR mismatched types
| _____________________________^
LL | | Ok(1);
| | - help: consider removing this semicolon
LL | | }
| |_^ expected enum `std::result::Result`, found ()
LL | fn foo() -> Result<u8, u64> { //~ ERROR mismatched types
| --- ^^^^^^^^^^^^^^^ expected enum `std::result::Result`, found ()
| |
| this function's body doesn't return
LL | Ok(1);
| - help: consider removing this semicolon
|
= note: expected type `std::result::Result<u8, u64>`
found type `()`

6
src/test/ui/issues/issue-32323.stderr
View File

@ -1,8 +1,10 @@
error[E0308]: mismatched types
--> $DIR/issue-32323.rs:5:49
--> $DIR/issue-32323.rs:5:30
|
LL | pub fn f<'a, T: Tr<'a>>() -> <T as Tr<'a>>::Out {}
| ^^ expected associated type, found ()
| - ^^^^^^^^^^^^^^^^^^ expected associated type, found ()
| |
| this function's body doesn't return
|
= note: expected type `<T as Tr<'a>>::Out`
found type `()`

16
src/test/ui/issues/issue-43162.stderr
View File

@ -11,15 +11,15 @@ LL | break {}; //~ ERROR E0268
| ^^^^^^^^ cannot break outside of a loop
error[E0308]: mismatched types
--> $DIR/issue-43162.rs:1:18
--> $DIR/issue-43162.rs:1:13
|
LL | fn foo() -> bool {
| __________________^
LL | | //~^ ERROR E0308
LL | | break true; //~ ERROR E0268
| | - help: consider removing this semicolon
LL | | }
| |_^ expected bool, found ()
LL | fn foo() -> bool {
| --- ^^^^ expected bool, found ()
| |
| this function's body doesn't return
LL | //~^ ERROR E0308
LL | break true; //~ ERROR E0268
| - help: consider removing this semicolon
|
= note: expected type `bool`
found type `()`

10
src/test/ui/issues/issue-44023.stderr
View File

@ -1,10 +1,10 @@
error[E0308]: mismatched types
--> $DIR/issue-44023.rs:5:42
--> $DIR/issue-44023.rs:5:36
|
LL | fn საჭმელად_გემრიელი_სადილი ( ) -> isize { //~ ERROR mismatched types
| __________________________________________^
LL | | }
| |_^ expected isize, found ()
LL | fn საჭმელად_გემრიელი_სადილი ( ) -> isize { //~ ERROR mismatched types
| ------------------------ ^^^^^ expected isize, found ()
| |
| this function's body doesn't return
|
= note: expected type `isize`
found type `()`

14
src/test/ui/issues/issue-6458-4.stderr
View File

@ -1,12 +1,12 @@
error[E0308]: mismatched types
--> $DIR/issue-6458-4.rs:1:40
--> $DIR/issue-6458-4.rs:1:20
|
LL | fn foo(b: bool) -> Result<bool,String> { //~ ERROR mismatched types
| ________________________________________^
LL | | Err("bar".to_string());
| | - help: consider removing this semicolon
LL | | }
| |_^ expected enum `std::result::Result`, found ()
LL | fn foo(b: bool) -> Result<bool,String> { //~ ERROR mismatched types
| --- ^^^^^^^^^^^^^^^^^^^ expected enum `std::result::Result`, found ()
| |
| this function's body doesn't return
LL | Err("bar".to_string());
| - help: consider removing this semicolon
|
= note: expected type `std::result::Result<bool, std::string::String>`
found type `()`

6
src/test/ui/liveness/liveness-forgot-ret.stderr
View File

@ -1,8 +1,10 @@
error[E0308]: mismatched types
--> $DIR/liveness-forgot-ret.rs:3:25
--> $DIR/liveness-forgot-ret.rs:3:19
|
LL | fn f(a: isize) -> isize { if god_exists(a) { return 5; }; }
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ expected isize, found ()
| - ^^^^^ expected isize, found () - expected because of this statement
| |
| this function's body doesn't return
|
= note: expected type `isize`
found type `()`

13
src/test/ui/liveness/liveness-missing-ret2.stderr
View File

@ -1,13 +1,10 @@
error[E0308]: mismatched types
--> $DIR/liveness-missing-ret2.rs:1:17
--> $DIR/liveness-missing-ret2.rs:1:11
|
LL | fn f() -> isize { //~ ERROR mismatched types
| _________________^
LL | | // Make sure typestate doesn't interpret this match expression as
LL | | // the function result
LL | | match true { true => { } _ => {} };
LL | | }
| |_^ expected isize, found ()
LL | fn f() -> isize { //~ ERROR mismatched types
| - ^^^^^ expected isize, found ()
| |
| this function's body doesn't return
|
= note: expected type `isize`
found type `()`

41
src/test/ui/liveness/liveness-return-last-stmt-semi.stderr
View File

@ -1,11 +1,11 @@
error[E0308]: mismatched types
--> $DIR/liveness-return-last-stmt-semi.rs:4:45
--> $DIR/liveness-return-last-stmt-semi.rs:4:41
|
LL | macro_rules! test { () => { fn foo() -> i32 { 1; } } }
| ^^^-^^
| | |
| | help: consider removing this semicolon
| expected i32, found ()
| --- ^^^ - help: consider removing this semicolon
| | |
| | expected i32, found ()
| this function's body doesn't return
...
LL | test!();
| -------- in this macro invocation
@ -14,35 +14,36 @@ LL | test!();
found type `()`
error[E0308]: mismatched types
--> $DIR/liveness-return-last-stmt-semi.rs:7:23
--> $DIR/liveness-return-last-stmt-semi.rs:7:19
|
LL | fn no_return() -> i32 {} //~ ERROR mismatched types
| ^^ expected i32, found ()
| --------- ^^^ expected i32, found ()
| |
| this function's body doesn't return
|
= note: expected type `i32`
found type `()`
error[E0308]: mismatched types
--> $DIR/liveness-return-last-stmt-semi.rs:9:23
--> $DIR/liveness-return-last-stmt-semi.rs:9:19
|
LL | fn bar(x: u32) -> u32 { //~ ERROR mismatched types
| _______________________^
LL | | x * 2;
| | - help: consider removing this semicolon
LL | | }
| |_^ expected u32, found ()
LL | fn bar(x: u32) -> u32 { //~ ERROR mismatched types
| --- ^^^ expected u32, found ()
| |
| this function's body doesn't return
LL | x * 2;
| - help: consider removing this semicolon
|
= note: expected type `u32`
found type `()`
error[E0308]: mismatched types
--> $DIR/liveness-return-last-stmt-semi.rs:13:23
--> $DIR/liveness-return-last-stmt-semi.rs:13:19
|
LL | fn baz(x: u64) -> u32 { //~ ERROR mismatched types
| _______________________^
LL | | x * 2;
LL | | }
| |_^ expected u32, found ()
LL | fn baz(x: u64) -> u32 { //~ ERROR mismatched types
| --- ^^^ expected u32, found ()
| |
| this function's body doesn't return
|
= note: expected type `u32`
found type `()`

6
src/test/ui/missing/missing-return.stderr
View File

@ -1,8 +1,10 @@
error[E0308]: mismatched types
--> $DIR/missing-return.rs:3:17
--> $DIR/missing-return.rs:3:11
|
LL | fn f() -> isize { }
| ^^^ expected isize, found ()
| - ^^^^^ expected isize, found ()
| |
| this function's body doesn't return
|
= note: expected type `isize`
found type `()`