Auto merge of rust-lang#10001 - Jarcho:issue_9866, r=llogiq

Fix ICE in `unused_rounding`

fixes rust-lang#9866
changelog: `unused_rounding`: Fix ICE when using the `_` separator

Author: bors

clippy_lints/src/unused_rounding.rs

@@ -1,4 +1,5 @@
 use clippy_utils::diagnostics::span_lint_and_sugg;
+use clippy_utils::source::snippet;
 use rustc_ast::ast::{Expr, ExprKind, MethodCall};
 use rustc_errors::Applicability;
 use rustc_lint::{EarlyContext, EarlyLintPass};
@@ -29,30 +30,24 @@ declare_clippy_lint! {
 }
 declare_lint_pass!(UnusedRounding => [UNUSED_ROUNDING]);
 
-fn is_useless_rounding(expr: &Expr) -> Option<(&str, String)> {
+fn is_useless_rounding<'a>(cx: &EarlyContext<'_>, expr: &'a Expr) -> Option<(&'a str, String)> {
     if let ExprKind::MethodCall(box MethodCall { seg:name_ident, receiver, .. }) = &expr.kind
         && let method_name = name_ident.ident.name.as_str()
         && (method_name == "ceil" || method_name == "round" || method_name == "floor")
         && let ExprKind::Lit(token_lit) = &receiver.kind
-        && token_lit.is_semantic_float() {
-            let mut f_str = token_lit.symbol.to_string();
-            let f = f_str.trim_end_matches('_').parse::<f64>().unwrap();
-            if let Some(suffix) = token_lit.suffix {
-                f_str.push_str(suffix.as_str());
-            }
-            if f.fract() == 0.0 {
-                Some((method_name, f_str))
-            } else {
-                None
-            }
+        && token_lit.is_semantic_float()
+        && let Ok(f) = token_lit.symbol.as_str().replace('_', "").parse::<f64>() {
+            (f.fract() == 0.0).then(||
+                (method_name, snippet(cx, receiver.span, "..").to_string())
+            )
         } else {
             None
         }
 }
 
 impl EarlyLintPass for UnusedRounding {
     fn check_expr(&mut self, cx: &EarlyContext<'_>, expr: &Expr) {
-        if let Some((method_name, float)) = is_useless_rounding(expr) {
+        if let Some((method_name, float)) = is_useless_rounding(cx, expr) {
             span_lint_and_sugg(
                 cx,
                 UNUSED_ROUNDING,

tests/ui/unused_rounding.fixed

@@ -11,4 +11,7 @@ fn main() {
     let _ = 3.3_f32.round();
     let _ = 3.3_f64.round();
     let _ = 3.0_f32;
+
+    let _ = 3_3.0_0_f32;
+    let _ = 3_3.0_1_f64.round();
 }

tests/ui/unused_rounding.rs

@@ -11,4 +11,7 @@ fn main() {
     let _ = 3.3_f32.round();
     let _ = 3.3_f64.round();
     let _ = 3.0_f32.round();
+
+    let _ = 3_3.0_0_f32.round();
+    let _ = 3_3.0_1_f64.round();
 }

tests/ui/unused_rounding.stderr

@@ -24,5 +24,11 @@ error: used the `round` method with a whole number float
 LL |     let _ = 3.0_f32.round();
    |             ^^^^^^^^^^^^^^^ help: remove the `round` method call: `3.0_f32`
 
-error: aborting due to 4 previous errors
+error: used the `round` method with a whole number float
+  --> $DIR/unused_rounding.rs:15:13
+   |
+LL |     let _ = 3_3.0_0_f32.round();
+   |             ^^^^^^^^^^^^^^^^^^^ help: remove the `round` method call: `3_3.0_0_f32`
+
+error: aborting due to 5 previous errors