emit errors when using RangeFrom and RangeTo

Author: TaKO8Ki

compiler/rustc_hir_typeck/src/fn_ctxt/suggestions.rs

@@ -1211,18 +1211,39 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
         expr: &hir::Expr<'_>,
         expected_ty: Ty<'tcx>,
     ) -> bool {
-        if let ExprKind::Struct(QPath::LangItem(LangItem::Range, ..), [start, _], _) = expr.kind
-            && expected_ty.is_floating_point()
-        {
-            err.span_suggestion_verbose(
-                self.tcx.sess.source_map().next_point(start.span),
-                "remove the unnecessary `.` operator to to use a floating point literal",
-                "",
-                Applicability::MachineApplicable,
-            );
-            return true;
+        if !expected_ty.is_floating_point() {
+            return false;
+        }
+        match expr.kind {
+            ExprKind::Struct(QPath::LangItem(LangItem::Range, ..), [start, end], _) => {
+                err.span_suggestion_verbose(
+                    start.span.shrink_to_hi().with_hi(end.span.lo()),
+                    "remove the unnecessary `.` operator for a floating point literal",
+                    '.',
+                    Applicability::MaybeIncorrect,
+                );
+                true
+            }
+            ExprKind::Struct(QPath::LangItem(LangItem::RangeFrom, ..), [start], _) => {
+                err.span_suggestion_verbose(
+                    expr.span.with_lo(start.span.hi()),
+                    "remove the unnecessary `.` operator for a floating point literal",
+                    '.',
+                    Applicability::MaybeIncorrect,
+                );
+                true
+            }
+            ExprKind::Struct(QPath::LangItem(LangItem::RangeTo, ..), [end], _) => {
+                err.span_suggestion_verbose(
+                    expr.span.until(end.span),
+                    "remove the unnecessary `.` operator and add an integer part for a floating point literal",
+                    "0.",
+                    Applicability::MaybeIncorrect,
+                );
+                true
+            }
+            _ => false,
         }
-        false
     }
 
     fn is_loop(&self, id: hir::HirId) -> bool {

src/test/ui/suggestions/unnecessary_dot_for_floating_point_literal.rs

@@ -1,6 +1,6 @@
 fn main() {
     let _: f64 = 0..10; //~ ERROR mismatched types
-    let _: f64 = 0..; //~ ERROR mismatched types
+    let _: f64 = 1..; //~ ERROR mismatched types
     let _: f64 = ..10; //~ ERROR mismatched types
     let _: f64 = std::ops::Range { start: 0, end: 1 }; //~ ERROR mismatched types
 }

src/test/ui/suggestions/unnecessary_dot_for_floating_point_literal.stderr

@@ -8,22 +8,25 @@ LL |     let _: f64 = 0..10;
    |
    = note: expected type `f64`
             found struct `std::ops::Range<{integer}>`
-help: remove the unnecessary `.` operator to to use a floating point literal
-   |
-LL -     let _: f64 = 0..10;
-LL +     let _: f64 = 0.10;
+help: remove the unnecessary `.` operator for a floating point literal
    |
+LL |     let _: f64 = 0.10;
+   |                   ~
 
 error[E0308]: mismatched types
   --> $DIR/unnecessary_dot_for_floating_point_literal.rs:3:18
    |
-LL |     let _: f64 = 0..;
+LL |     let _: f64 = 1..;
    |            ---   ^^^ expected `f64`, found struct `RangeFrom`
    |            |
    |            expected due to this
    |
    = note: expected type `f64`
             found struct `RangeFrom<{integer}>`
+help: remove the unnecessary `.` operator for a floating point literal
+   |
+LL |     let _: f64 = 1.;
+   |                   ~
 
 error[E0308]: mismatched types
   --> $DIR/unnecessary_dot_for_floating_point_literal.rs:4:18
@@ -35,6 +38,10 @@ LL |     let _: f64 = ..10;
    |
    = note: expected type `f64`
             found struct `RangeTo<{integer}>`
+help: remove the unnecessary `.` operator and add an integer part for a floating point literal
+   |
+LL |     let _: f64 = 0.10;
+   |                  ~~
 
 error[E0308]: mismatched types
   --> $DIR/unnecessary_dot_for_floating_point_literal.rs:5:18