Add check from_expansion

clippy_lints/src/redundant_type_annotations.rs

@@ -102,7 +102,8 @@ fn is_redundant_in_func_call<'tcx>(
 impl LateLintPass<'_> for RedundantTypeAnnotations {
     fn check_local<'tcx>(&mut self, cx: &LateContext<'tcx>, local: &'tcx rustc_hir::Local<'tcx>) {
         // type annotation part
-        if let Some(ty) = &local.ty
+        if !local.span.from_expansion()
+            && let Some(ty) = &local.ty
             && let hir::TyKind::Path(ty_path) = &ty.kind
             && let hir::QPath::Resolved(_, resolved_path_ty) = ty_path
 

tests/ui/redundant_type_annotations.rs

@@ -1,73 +1,130 @@
 #![allow(unused)]
 #![warn(clippy::redundant_type_annotations)]
 
-struct A;
-enum E {
+#[derive(Debug, Default)]
+struct Cake<T> {
+    _data: T,
+}
+
+fn make_something<T: Default>() -> T {
+    T::default()
+}
+
+fn make_cake<T: Default>() -> Cake<T> {
+    Cake::<T>::default()
+}
+
+struct Pie {
+    inner: u32,
+}
+
+enum Pizza {
     One,
     Two,
 }
 
-fn f() -> String {
+fn return_a_string() -> String {
     String::new()
 }
 
-fn f_struct() -> A {
-    A
+fn return_a_struct() -> Pie {
+    Pie { inner: 5 }
 }
 
-fn f_enum() -> E {
-    E::One
+fn return_an_enum() -> Pizza {
+    Pizza::One
 }
 
-struct ATest2 {
-    inner: u32,
+fn return_an_int() -> u32 {
+    5
 }
 
-impl ATest2 {
-    fn func(&self) -> u32 {
+impl Pie {
+    fn return_an_int(&self) -> u32 {
         self.inner
     }
 
-    fn a(&self) {
-        let v: u32 = self.func(); // This should lint but doesn't (MethodCall)
-    }
-
-    fn get_num() -> u32 {
+    fn associated_return_an_int() -> u32 {
         5
     }
 
     fn new() -> Self {
         Self { inner: 5 }
     }
 
-    fn get_string() -> String {
+    fn associated_return_a_string() -> String {
         String::from("")
     }
+
+    fn test_method_call(&self) {
+        let v: u32 = self.return_an_int(); // This should lint but doesn't (MethodCall)
+    }
 }
 
-fn f_prim() -> u32 {
-    5
+fn test_generics() {
+    // The type annotation is needed to determine T
+    let _c: Cake<i32> = make_something();
+
+    // The type annotation is needed to determine the topic
+    let _c: Cake<u8> = make_cake();
+}
+
+fn test_non_locals() {
+    // This shouldn't lint
+    fn _arg(x: u32) -> u32 {
+        x
+    }
+
+    // This could lint, but probably shouldn't
+    let _closure_arg = |x: u32| x;
+}
+
+fn test_complex_types() {
+    // Shouldn't lint, since the literal will be i32 otherwise
+    let _u8: u8 = 128;
+
+    // Should lint
+    let _tuple_i32: (i32, i32) = (12, 13);
+
+    // Shouldn't lint, since the tuple will be i32 otherwise
+    let _tuple_u32: (u32, u32) = (1, 2);
+
+    // Should lint, since the type is determined by the init value
+    let _tuple_u32: (u32, u32) = (3_u32, 4_u32);
+
+    // Should lint
+    let _array: [i32; 3] = [5, 6, 7];
+
+    // Shouldn't lint
+    let _array: [u32; 2] = [8, 9];
 }
 
-fn main() {
-    let a: String = f();
+fn test_functions() {
+    // Everything here should lint
 
-    let a: A = f_struct();
+    let _return: String = return_a_string();
 
-    let a: E = f_enum();
+    let _return: Pie = return_a_struct();
 
-    let a: u32 = f_prim();
+    let _return: Pizza = return_an_enum();
 
-    let a: String = String::new();
+    let _return: u32 = return_an_int();
 
-    let st: ATest2 = ATest2::new();
-    let a: u32 = st.func(); // this should lint but doesn't (MethodCall)
+    let _return: String = String::new();
 
-    let a: String = String::from("test");
+    let new_pie: Pie = Pie::new();
 
-    let a: u32 = u32::MAX;
+    let _return: u32 = new_pie.return_an_int(); // this should lint but doesn't (MethodCall)
 
-    let a: u32 = ATest2::get_num();
+    let _return: String = String::from("test");
 
-    let a: String = ATest2::get_string();
+    let _return: u32 = Pie::associated_return_an_int();
+
+    let _return: String = Pie::associated_return_a_string();
+}
+
+fn test_simple_types() {
+    let _var: u32 = u32::MAX;
 }
+
+fn main() {}

tests/ui/redundant_type_annotations.stderr

@@ -1,58 +1,58 @@
 error: redundant type annotation
-  --> $DIR/redundant_type_annotations.rs:53:5
+  --> $DIR/redundant_type_annotations.rs:107:5
    |
-LL |     let a: String = f();
-   |     ^^^^^^^^^^^^^^^^^^^^
+LL |     let _return: String = return_a_string();
+   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
    |
    = note: `-D clippy::redundant-type-annotations` implied by `-D warnings`
 
 error: redundant type annotation
-  --> $DIR/redundant_type_annotations.rs:55:5
+  --> $DIR/redundant_type_annotations.rs:109:5
    |
-LL |     let a: A = f_struct();
-   |     ^^^^^^^^^^^^^^^^^^^^^^
+LL |     let _return: Pie = return_a_struct();
+   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
 error: redundant type annotation
-  --> $DIR/redundant_type_annotations.rs:57:5
+  --> $DIR/redundant_type_annotations.rs:111:5
    |
-LL |     let a: E = f_enum();
-   |     ^^^^^^^^^^^^^^^^^^^^
+LL |     let _return: Pizza = return_an_enum();
+   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
 error: redundant type annotation
-  --> $DIR/redundant_type_annotations.rs:59:5
+  --> $DIR/redundant_type_annotations.rs:113:5
    |
-LL |     let a: u32 = f_prim();
-   |     ^^^^^^^^^^^^^^^^^^^^^^
+LL |     let _return: u32 = return_an_int();
+   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
 error: redundant type annotation
-  --> $DIR/redundant_type_annotations.rs:61:5
+  --> $DIR/redundant_type_annotations.rs:115:5
    |
-LL |     let a: String = String::new();
-   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+LL |     let _return: String = String::new();
+   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
 error: redundant type annotation
-  --> $DIR/redundant_type_annotations.rs:63:5
+  --> $DIR/redundant_type_annotations.rs:117:5
    |
-LL |     let st: ATest2 = ATest2::new();
-   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+LL |     let new_pie: Pie = Pie::new();
+   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
 error: redundant type annotation
-  --> $DIR/redundant_type_annotations.rs:68:5
+  --> $DIR/redundant_type_annotations.rs:123:5
    |
-LL |     let a: u32 = u32::MAX;
-   |     ^^^^^^^^^^^^^^^^^^^^^^
+LL |     let _return: u32 = Pie::associated_return_an_int();
+   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
 error: redundant type annotation
-  --> $DIR/redundant_type_annotations.rs:70:5
+  --> $DIR/redundant_type_annotations.rs:125:5
    |
-LL |     let a: u32 = ATest2::get_num();
-   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+LL |     let _return: String = Pie::associated_return_a_string();
+   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
 error: redundant type annotation
-  --> $DIR/redundant_type_annotations.rs:72:5
+  --> $DIR/redundant_type_annotations.rs:129:5
    |
-LL |     let a: String = ATest2::get_string();
-   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+LL |     let _var: u32 = u32::MAX;
+   |     ^^^^^^^^^^^^^^^^^^^^^^^^^
 
 error: aborting due to 9 previous errors