Auto merge of #5680 - ebroto:3792_let_return, r=Manishearth

let_and_return: avoid "does not live long enough" errors

EDIT: Add #3324 to the list of fixes

<details>
<summary>Description of old impl</summary>
<br>
Avoid suggesting turning the RHS expression of the last statement into the block tail expression if a temporary borrows from a local that would be destroyed before.

This is my first incursion into MIR so there's probably room for improvement!
</details>

Avoid linting if the return type of some method or function called in the last statement has a lifetime parameter.

changelog: Fix false positive in [`let_and_return`]

Fixes #3792
Fixes #3324

1 files changed, 5 insertions, 3 deletions

diff --git a/clippy_lints/src/lib.rs b/clippy_lints/src/lib.rs
index 9809f953d67..cd258c7b506 100644
--- a/clippy_lints/src/lib.rs
+++ b/clippy_lints/src/lib.rs
@@ -241,6 +241,7 @@ mod large_const_arrays;
 mod large_enum_variant;
 mod large_stack_arrays;
 mod len_zero;
+mod let_and_return;
 mod let_if_seq;
 mod let_underscore;
 mod lifetimes;
@@ -599,6 +600,7 @@ pub fn register_plugins(store: &mut rustc_lint::LintStore, sess: &Session, conf:
         &large_stack_arrays::LARGE_STACK_ARRAYS,
         &len_zero::LEN_WITHOUT_IS_EMPTY,
         &len_zero::LEN_ZERO,
+        &let_and_return::LET_AND_RETURN,
         &let_if_seq::USELESS_LET_IF_SEQ,
         &let_underscore::LET_UNDERSCORE_LOCK,
         &let_underscore::LET_UNDERSCORE_MUST_USE,
@@ -775,7 +777,6 @@ pub fn register_plugins(store: &mut rustc_lint::LintStore, sess: &Session, conf:
         &regex::INVALID_REGEX,
         &regex::REGEX_MACRO,
         &regex::TRIVIAL_REGEX,
-        &returns::LET_AND_RETURN,
         &returns::NEEDLESS_RETURN,
         &returns::UNUSED_UNIT,
         &serde_api::SERDE_API_MISUSE,
@@ -1026,6 +1027,7 @@ pub fn register_plugins(store: &mut rustc_lint::LintStore, sess: &Session, conf:
     store.register_early_pass(|| box formatting::Formatting);
     store.register_early_pass(|| box misc_early::MiscEarlyLints);
     store.register_early_pass(|| box returns::Return);
+    store.register_late_pass(|| box let_and_return::LetReturn);
     store.register_early_pass(|| box collapsible_if::CollapsibleIf);
     store.register_early_pass(|| box items_after_statements::ItemsAfterStatements);
     store.register_early_pass(|| box precedence::Precedence);
@@ -1270,6 +1272,7 @@ pub fn register_plugins(store: &mut rustc_lint::LintStore, sess: &Session, conf:
         LintId::of(&large_enum_variant::LARGE_ENUM_VARIANT),
         LintId::of(&len_zero::LEN_WITHOUT_IS_EMPTY),
         LintId::of(&len_zero::LEN_ZERO),
+        LintId::of(&let_and_return::LET_AND_RETURN),
         LintId::of(&let_underscore::LET_UNDERSCORE_LOCK),
         LintId::of(&lifetimes::EXTRA_UNUSED_LIFETIMES),
         LintId::of(&lifetimes::NEEDLESS_LIFETIMES),
@@ -1395,7 +1398,6 @@ pub fn register_plugins(store: &mut rustc_lint::LintStore, sess: &Session, conf:
         LintId::of(&regex::INVALID_REGEX),
         LintId::of(&regex::REGEX_MACRO),
         LintId::of(&regex::TRIVIAL_REGEX),
-        LintId::of(&returns::LET_AND_RETURN),
         LintId::of(&returns::NEEDLESS_RETURN),
         LintId::of(&returns::UNUSED_UNIT),
         LintId::of(&serde_api::SERDE_API_MISUSE),
@@ -1480,6 +1482,7 @@ pub fn register_plugins(store: &mut rustc_lint::LintStore, sess: &Session, conf:
         LintId::of(&inherent_to_string::INHERENT_TO_STRING),
         LintId::of(&len_zero::LEN_WITHOUT_IS_EMPTY),
         LintId::of(&len_zero::LEN_ZERO),
+        LintId::of(&let_and_return::LET_AND_RETURN),
         LintId::of(&literal_representation::INCONSISTENT_DIGIT_GROUPING),
         LintId::of(&loops::EMPTY_LOOP),
         LintId::of(&loops::FOR_KV_MAP),
@@ -1532,7 +1535,6 @@ pub fn register_plugins(store: &mut rustc_lint::LintStore, sess: &Session, conf:
         LintId::of(&redundant_static_lifetimes::REDUNDANT_STATIC_LIFETIMES),
         LintId::of(&regex::REGEX_MACRO),
         LintId::of(&regex::TRIVIAL_REGEX),
-        LintId::of(&returns::LET_AND_RETURN),
         LintId::of(&returns::NEEDLESS_RETURN),
         LintId::of(&returns::UNUSED_UNIT),
         LintId::of(&single_component_path_imports::SINGLE_COMPONENT_PATH_IMPORTS),