Set turbofish for every sugg and add more test cases

Author: ThibsG

clippy_lints/src/methods/mod.rs

@@ -4095,11 +4095,7 @@ fn lint_from_iter(cx: &LateContext<'_>, expr: &hir::Expr<'_>, args: &[hir::Expr<
         then {
             // `expr` implements `FromIterator` trait
             let iter_expr = sugg::Sugg::hir(cx, &args[0], "..").maybe_par();
-            let sugg = if higher::range(&args[0]).is_some() {
-                format!("{}.collect::<{}>()", iter_expr, ty)
-            } else {
-                format!("{}.collect()", iter_expr)
-            };
+            let sugg = format!("{}.collect::<{}>()", iter_expr, ty);
             span_lint_and_sugg(
                 cx,
                 FROM_ITER_INSTEAD_OF_COLLECT,

tests/ui/from_iter_instead_of_collect.fixed

@@ -0,0 +1,34 @@
+// run-rustfix
+
+#![warn(clippy::from_iter_instead_of_collect)]
+#![allow(unused_imports)]
+
+use std::collections::{BTreeMap, BTreeSet, HashMap, VecDeque};
+use std::iter::FromIterator;
+
+fn main() {
+    let iter_expr = std::iter::repeat(5).take(5);
+    let _ = iter_expr.collect::<std::vec::Vec<i32>>();
+
+    let _ = vec![5, 5, 5, 5].iter().enumerate().collect::<std::collections::HashMap<usize, &i8>>();
+
+    Vec::from_iter(vec![42u32]);
+
+    let a = vec![0, 1, 2];
+    assert_eq!(a, (0..3).collect::<std::vec::Vec<i32>>());
+
+    let mut b = (0..3).collect::<std::collections::VecDeque<i32>>();
+    b.push_back(4);
+
+    let values = [(0, 'a'), (1, 'b'), (2, 'c'), (3, 'd')];
+    let bm = values.iter().cloned().collect::<std::collections::BTreeMap<i32, char>>();
+    let mut bar = bm.range(0..2).collect::<std::collections::BTreeMap<&i32, &char>>();
+    bar.insert(&4, &'e');
+
+    let mut bts = (0..3).collect::<std::collections::BTreeSet<i32>>();
+    bts.insert(2);
+    {
+        use std::collections;
+        let _ = (0..3).collect::<std::collections::BTreeSet<i32>>();
+    }
+}

tests/ui/from_iter_instead_of_collect.rs

@@ -1,13 +1,16 @@
+// run-rustfix
+
 #![warn(clippy::from_iter_instead_of_collect)]
+#![allow(unused_imports)]
 
-use std::collections::{HashMap, VecDeque};
+use std::collections::{BTreeMap, BTreeSet, HashMap, VecDeque};
 use std::iter::FromIterator;
 
 fn main() {
     let iter_expr = std::iter::repeat(5).take(5);
-    Vec::from_iter(iter_expr);
+    let _ = Vec::from_iter(iter_expr);
 
-    HashMap::<usize, &i8>::from_iter(vec![5, 5, 5, 5].iter().enumerate());
+    let _ = HashMap::<usize, &i8>::from_iter(vec![5, 5, 5, 5].iter().enumerate());
 
     Vec::from_iter(vec![42u32]);
 
@@ -16,4 +19,16 @@ fn main() {
 
     let mut b = VecDeque::from_iter(0..3);
     b.push_back(4);
+
+    let values = [(0, 'a'), (1, 'b'), (2, 'c'), (3, 'd')];
+    let bm = BTreeMap::from_iter(values.iter().cloned());
+    let mut bar = BTreeMap::from_iter(bm.range(0..2));
+    bar.insert(&4, &'e');
+
+    let mut bts = BTreeSet::from_iter(0..3);
+    bts.insert(2);
+    {
+        use std::collections;
+        let _ = collections::BTreeSet::from_iter(0..3);
+    }
 }

tests/ui/from_iter_instead_of_collect.stderr

@@ -1,28 +1,52 @@
 error: usage of `FromIterator::from_iter`
-  --> $DIR/from_iter_instead_of_collect.rs:8:5
+  --> $DIR/from_iter_instead_of_collect.rs:11:13
    |
-LL |     Vec::from_iter(iter_expr);
-   |     ^^^^^^^^^^^^^^^^^^^^^^^^^ help: use `.collect()` instead of `::from_iter()`: `iter_expr.collect()`
+LL |     let _ = Vec::from_iter(iter_expr);
+   |             ^^^^^^^^^^^^^^^^^^^^^^^^^ help: use `.collect()` instead of `::from_iter()`: `iter_expr.collect::<std::vec::Vec<i32>>()`
    |
    = note: `-D clippy::from-iter-instead-of-collect` implied by `-D warnings`
 
 error: usage of `FromIterator::from_iter`
-  --> $DIR/from_iter_instead_of_collect.rs:10:5
+  --> $DIR/from_iter_instead_of_collect.rs:13:13
    |
-LL |     HashMap::<usize, &i8>::from_iter(vec![5, 5, 5, 5].iter().enumerate());
-   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: use `.collect()` instead of `::from_iter()`: `vec![5, 5, 5, 5].iter().enumerate().collect()`
+LL |     let _ = HashMap::<usize, &i8>::from_iter(vec![5, 5, 5, 5].iter().enumerate());
+   |             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: use `.collect()` instead of `::from_iter()`: `vec![5, 5, 5, 5].iter().enumerate().collect::<std::collections::HashMap<usize, &i8>>()`
 
 error: usage of `FromIterator::from_iter`
-  --> $DIR/from_iter_instead_of_collect.rs:15:19
+  --> $DIR/from_iter_instead_of_collect.rs:18:19
    |
 LL |     assert_eq!(a, Vec::from_iter(0..3));
    |                   ^^^^^^^^^^^^^^^^^^^^ help: use `.collect()` instead of `::from_iter()`: `(0..3).collect::<std::vec::Vec<i32>>()`
 
 error: usage of `FromIterator::from_iter`
-  --> $DIR/from_iter_instead_of_collect.rs:17:17
+  --> $DIR/from_iter_instead_of_collect.rs:20:17
    |
 LL |     let mut b = VecDeque::from_iter(0..3);
    |                 ^^^^^^^^^^^^^^^^^^^^^^^^^ help: use `.collect()` instead of `::from_iter()`: `(0..3).collect::<std::collections::VecDeque<i32>>()`
 
-error: aborting due to 4 previous errors
+error: usage of `FromIterator::from_iter`
+  --> $DIR/from_iter_instead_of_collect.rs:24:14
+   |
+LL |     let bm = BTreeMap::from_iter(values.iter().cloned());
+   |              ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: use `.collect()` instead of `::from_iter()`: `values.iter().cloned().collect::<std::collections::BTreeMap<i32, char>>()`
+
+error: usage of `FromIterator::from_iter`
+  --> $DIR/from_iter_instead_of_collect.rs:25:19
+   |
+LL |     let mut bar = BTreeMap::from_iter(bm.range(0..2));
+   |                   ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: use `.collect()` instead of `::from_iter()`: `bm.range(0..2).collect::<std::collections::BTreeMap<&i32, &char>>()`
+
+error: usage of `FromIterator::from_iter`
+  --> $DIR/from_iter_instead_of_collect.rs:28:19
+   |
+LL |     let mut bts = BTreeSet::from_iter(0..3);
+   |                   ^^^^^^^^^^^^^^^^^^^^^^^^^ help: use `.collect()` instead of `::from_iter()`: `(0..3).collect::<std::collections::BTreeSet<i32>>()`
+
+error: usage of `FromIterator::from_iter`
+  --> $DIR/from_iter_instead_of_collect.rs:32:17
+   |
+LL |         let _ = collections::BTreeSet::from_iter(0..3);
+   |                 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: use `.collect()` instead of `::from_iter()`: `(0..3).collect::<std::collections::BTreeSet<i32>>()`
+
+error: aborting due to 8 previous errors