don't create variable bindings just to return the bound value immedia…

…tely (clippy::let_and_return)

src/liballoc/slice.rs

@@ -145,8 +145,7 @@ mod hack {
         unsafe {
             let len = b.len();
             let b = Box::into_raw(b);
-            let xs = Vec::from_raw_parts(b as *mut T, len, len);
-            xs
+            Vec::from_raw_parts(b as *mut T, len, len)
         }
     }
 

src/librustc/hir/map/mod.rs

@@ -1038,9 +1038,7 @@ pub(super) fn index_hir<'tcx>(tcx: TyCtxt<'tcx>, cnum: CrateNum) -> &'tcx Indexe
         collector.finalize_and_compute_crate_hash(crate_disambiguator, &*tcx.cstore, cmdline_args)
     };
 
-    let map = tcx.arena.alloc(IndexedHir { crate_hash, map });
-
-    map
+    tcx.arena.alloc(IndexedHir { crate_hash, map })
 }
 
 /// Identical to the `PpAnn` implementation for `hir::Crate`,

src/librustc_codegen_ssa/back/rpath.rs

@@ -81,9 +81,7 @@ fn get_rpaths(config: &mut RPathConfig<'_>, libs: &[PathBuf]) -> Vec<String> {
     rpaths.extend_from_slice(&fallback_rpaths);
 
     // Remove duplicates
-    let rpaths = minimize_rpaths(&rpaths);
-
-    rpaths
+    minimize_rpaths(&rpaths)
 }
 
 fn get_rpaths_relative_to_output(config: &mut RPathConfig<'_>, libs: &[PathBuf]) -> Vec<String> {

src/librustc_codegen_ssa/back/write.rs

@@ -288,7 +288,7 @@ fn generate_lto_work<B: ExtraBackendMethods>(
         B::run_thin_lto(cgcx, needs_thin_lto, import_only_modules).unwrap_or_else(|e| e.raise())
     };
 
-    let result = lto_modules
+    lto_modules
         .into_iter()
         .map(|module| {
             let cost = module.cost();
@@ -303,9 +303,7 @@ fn generate_lto_work<B: ExtraBackendMethods>(
                 0,
             )
         }))
-        .collect();
-
-    result
+        .collect()
 }
 
 pub struct CompiledModules {

src/librustc_infer/infer/canonical/canonicalizer.rs

@@ -555,7 +555,7 @@ impl<'cx, 'tcx> Canonicalizer<'cx, 'tcx> {
         // avoid allocations in those cases. We also don't use `indices` to
         // determine if a kind has been seen before until the limit of 8 has
         // been exceeded, to also avoid allocations for `indices`.
-        let var = if !var_values.spilled() {
+        if !var_values.spilled() {
             // `var_values` is stack-allocated. `indices` isn't used yet. Do a
             // direct linear search of `var_values`.
             if let Some(idx) = var_values.iter().position(|&k| k == kind) {
@@ -589,9 +589,7 @@ impl<'cx, 'tcx> Canonicalizer<'cx, 'tcx> {
                 assert_eq!(variables.len(), var_values.len());
                 BoundVar::new(variables.len() - 1)
             })
-        };
-
-        var
+        }
     }
 
     /// Shorthand helper that creates a canonical region variable for

src/librustc_metadata/dynamic_lib.rs

@@ -94,14 +94,12 @@ mod dl {
             let result = f();
 
             let last_error = libc::dlerror() as *const _;
-            let ret = if ptr::null() == last_error {
+            if ptr::null() == last_error {
                 Ok(result)
             } else {
                 let s = CStr::from_ptr(last_error).to_bytes();
                 Err(str::from_utf8(s).unwrap().to_owned())
-            };
-
-            ret
+            }
         }
     }
 

src/librustc_mir/dataflow/move_paths/builder.rs

@@ -184,14 +184,13 @@ impl<'b, 'a, 'tcx> Gatherer<'b, 'a, 'tcx> {
             ..
         } = self.builder;
         *rev_lookup.projections.entry((base, elem.lift())).or_insert_with(move || {
-            let path = MoveDataBuilder::new_move_path(
+            MoveDataBuilder::new_move_path(
                 move_paths,
                 path_map,
                 init_path_map,
                 Some(base),
                 mk_place(*tcx),
-            );
-            path
+            )
         })
     }
 

src/librustc_mir/transform/const_prop.rs

@@ -400,7 +400,7 @@ impl<'mir, 'tcx> ConstPropagator<'mir, 'tcx> {
     where
         F: FnOnce(&mut Self) -> InterpResult<'tcx, T>,
     {
-        let r = match f(self) {
+        match f(self) {
             Ok(val) => Some(val),
             Err(error) => {
                 // Some errors shouldn't come up because creating them causes
@@ -414,8 +414,7 @@ impl<'mir, 'tcx> ConstPropagator<'mir, 'tcx> {
                 );
                 None
             }
-        };
-        r
+        }
     }
 
     fn eval_constant(&mut self, c: &Constant<'tcx>, source_info: SourceInfo) -> Option<OpTy<'tcx>> {

src/librustc_parse/lexer/mod.rs

@@ -179,14 +179,12 @@ impl<'a> StringReader<'a> {
             rustc_lexer::TokenKind::LineComment => {
                 let string = self.str_from(start);
                 // comments with only more "/"s are not doc comments
-                let tok = if comments::is_line_doc_comment(string) {
+                if comments::is_line_doc_comment(string) {
                     self.forbid_bare_cr(start, string, "bare CR not allowed in doc-comment");
                     token::DocComment(Symbol::intern(string))
                 } else {
                     token::Comment
-                };
-
-                tok
+                }
             }
             rustc_lexer::TokenKind::BlockComment { terminated } => {
                 let string = self.str_from(start);
@@ -204,14 +202,12 @@ impl<'a> StringReader<'a> {
                     self.fatal_span_(start, last_bpos, msg).raise();
                 }
 
-                let tok = if is_doc_comment {
+                if is_doc_comment {
                     self.forbid_bare_cr(start, string, "bare CR not allowed in block doc-comment");
                     token::DocComment(Symbol::intern(string))
                 } else {
                     token::Comment
-                };
-
-                tok
+                }
             }
             rustc_lexer::TokenKind::Whitespace => token::Whitespace,
             rustc_lexer::TokenKind::Ident | rustc_lexer::TokenKind::RawIdent => {

src/librustc_resolve/diagnostics.rs

@@ -59,8 +59,7 @@ crate struct ImportSuggestion {
 /// `source_map` functions and this function to something more robust.
 fn reduce_impl_span_to_impl_keyword(sm: &SourceMap, impl_span: Span) -> Span {
     let impl_span = sm.span_until_char(impl_span, '<');
-    let impl_span = sm.span_until_whitespace(impl_span);
-    impl_span
+    sm.span_until_whitespace(impl_span)
 }
 
 impl<'a> Resolver<'a> {

src/librustc_resolve/lib.rs

@@ -1871,16 +1871,15 @@ impl<'a> Resolver<'a> {
                 // No adjustments
             }
         }
-        let result = self.resolve_ident_in_module_unadjusted_ext(
+        self.resolve_ident_in_module_unadjusted_ext(
             module,
             ident,
             ns,
             adjusted_parent_scope,
             false,
             record_used,
             path_span,
-        );
-        result
+        )
     }
 
     fn resolve_crate_root(&mut self, ident: Ident) -> Module<'a> {

src/librustc_typeck/check/expr.rs

@@ -1069,16 +1069,13 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
             }
         });
 
-        let elt_ts_iter = elts.iter().enumerate().map(|(i, e)| {
-            let t = match flds {
-                Some(ref fs) if i < fs.len() => {
-                    let ety = fs[i].expect_ty();
-                    self.check_expr_coercable_to_type(&e, ety);
-                    ety
-                }
-                _ => self.check_expr_with_expectation(&e, NoExpectation),
-            };
-            t
+        let elt_ts_iter = elts.iter().enumerate().map(|(i, e)| match flds {
+            Some(ref fs) if i < fs.len() => {
+                let ety = fs[i].expect_ty();
+                self.check_expr_coercable_to_type(&e, ety);
+                ety
+            }
+            _ => self.check_expr_with_expectation(&e, NoExpectation),
         });
         let tuple = self.tcx.mk_tup(elt_ts_iter);
         if tuple.references_error() {

src/librustc_typeck/check/mod.rs

@@ -3654,14 +3654,12 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
 
         // Otherwise, fall back to the immutable version.
         let (imm_tr, imm_op) = self.resolve_place_op(op, false);
-        let method = match (method, imm_tr) {
+        match (method, imm_tr) {
             (None, Some(trait_did)) => {
                 self.lookup_method_in_trait(span, imm_op, trait_did, base_ty, Some(arg_tys))
             }
             (method, _) => method,
-        };
-
-        method
+        }
     }
 
     fn check_method_argument_types(

src/librustdoc/clean/utils.rs

@@ -507,7 +507,7 @@ pub fn print_const(cx: &DocContext<'_>, n: &'tcx ty::Const<'_>) -> String {
 }
 
 pub fn print_evaluated_const(cx: &DocContext<'_>, def_id: DefId) -> Option<String> {
-    let value = cx.tcx.const_eval_poly(def_id).ok().and_then(|val| {
+    cx.tcx.const_eval_poly(def_id).ok().and_then(|val| {
         let ty = cx.tcx.type_of(def_id);
         match (val, &ty.kind) {
             (_, &ty::Ref(..)) => None,
@@ -518,9 +518,7 @@ pub fn print_evaluated_const(cx: &DocContext<'_>, def_id: DefId) -> Option<Strin
             }
             _ => None,
         }
-    });
-
-    value
+    })
 }
 
 fn format_integer_with_underscore_sep(num: &str) -> String {

src/librustdoc/html/render/cache.rs

@@ -666,13 +666,12 @@ fn get_index_search_type(item: &clean::Item) -> Option<IndexItemFunctionType> {
 }
 
 fn get_index_type(clean_type: &clean::Type) -> RenderType {
-    let t = RenderType {
+    RenderType {
         ty: clean_type.def_id(),
         idx: None,
         name: get_index_type_name(clean_type, true).map(|s| s.to_ascii_lowercase()),
         generics: get_generics(clean_type),
-    };
-    t
+    }
 }
 
 fn get_index_type_name(clean_type: &clean::Type, accept_generic: bool) -> Option<String> {