Rewrite check to account for floating point literals

Author: DennisOSRM

clippy_lints/src/lib.rs

@@ -747,7 +747,7 @@ pub fn register_plugins(store: &mut rustc_lint::LintStore, sess: &Session, conf:
     store.register_early_pass(|| Box::new(collapsible_if::CollapsibleIf));
     store.register_early_pass(|| Box::new(items_after_statements::ItemsAfterStatements));
     store.register_early_pass(|| Box::new(precedence::Precedence));
-    store.register_early_pass(|| Box::new(needless_parens_on_range_literal::NeedlessParensOnRangeLiteral));
+    store.register_late_pass(|| Box::new(needless_parens_on_range_literal::NeedlessParensOnRangeLiteral));
     store.register_early_pass(|| Box::new(needless_continue::NeedlessContinue));
     store.register_early_pass(|| Box::new(redundant_else::RedundantElse));
     store.register_late_pass(|| Box::new(create_dir::CreateDir));

clippy_lints/src/needless_parens_on_range_literal.rs

@@ -17,10 +17,17 @@
 //! ```
 //!
 
-use clippy_utils::{diagnostics::span_lint_and_then, source::snippet_opt};
-use rustc_ast::ast::{Expr, ExprKind};
+use clippy_utils::{
+    diagnostics::span_lint_and_then,
+    higher,
+    source::{snippet, snippet_opt},
+};
+
+use rustc_ast::ast;
 use rustc_errors::Applicability;
-use rustc_lint::{EarlyContext, EarlyLintPass};
+use rustc_hir::{Expr, ExprKind};
+
+use rustc_lint::{LateContext, LateLintPass};
 use rustc_session::{declare_lint_pass, declare_tool_lint};
 
 declare_clippy_lint! {
@@ -40,27 +47,47 @@ declare_clippy_lint! {
 
 declare_lint_pass!(NeedlessParensOnRangeLiteral => [NEEDLESS_PARENS_ON_RANGE_LITERAL]);
 
-fn check_for_parens(cx: &EarlyContext<'_>, e: &Expr) {
-    if_chain! {
-      if let ExprKind::Paren(ref start_statement) = &e.kind;
-    if let ExprKind::Lit(ref literal) = start_statement.kind;
-    then {
-      span_lint_and_then(cx, NEEDLESS_PARENS_ON_RANGE_LITERAL, e.span,
-        "needless parenthesis on range literal can be removed",
-        |diag| {
-                if let Some(suggestion) = snippet_opt(cx, literal.span) {
-                  diag.span_suggestion(e.span, "try", suggestion, Applicability::MachineApplicable);
-              }
-        });
+fn snippet_enclosed_in_parenthesis(snippet: &str) -> bool {
+    snippet.starts_with('(') && snippet.ends_with(')')
+}
+
+fn check_for_parens(cx: &LateContext<'_>, e: &Expr<'_>, is_start: bool) {
+    if is_start &&
+    let ExprKind::Lit(ref literal) = e.kind &&
+    let ast::LitKind::Float(_sym, ast::LitFloatType::Unsuffixed) = literal.node
+    {
+        // don't check floating point literals on the start expression of a range
+        return;
     }
+    if_chain! {
+        if let ExprKind::Lit(ref literal) = e.kind;
+        // the indicator that paranthese surround the literal is that span of the expression and the literal differ
+        if (literal.span.data().hi - literal.span.data().lo) != (e.span.data().hi - e.span.data().lo);
+        // inspect the source code of the expression for parenthesis
+        if snippet_enclosed_in_parenthesis(&snippet(cx, e.span, ""));
+        then {
+            span_lint_and_then(cx, NEEDLESS_PARENS_ON_RANGE_LITERAL, e.span,
+                "needless parenthesis on range literal can be removed",
+                |diag| {
+                        if let Some(suggestion) = snippet_opt(cx, literal.span) {
+                        diag.span_suggestion(e.span, "try", suggestion, Applicability::MachineApplicable);
+                    }
+                });
+        }
     }
 }
 
-impl EarlyLintPass for NeedlessParensOnRangeLiteral {
-    fn check_expr(&mut self, cx: &EarlyContext<'_>, e: &Expr) {
-        if let ExprKind::Range(Some(start), Some(end), _) = &e.kind {
-            check_for_parens(cx, start);
-            check_for_parens(cx, end);
+impl<'tcx> LateLintPass<'tcx> for NeedlessParensOnRangeLiteral {
+    fn check_expr(&mut self, cx: &LateContext<'tcx>, expr: &'tcx Expr<'_>) {
+        // if let higher::Range { start, end, limits } = &e.kind {
+        if let Some(higher::Range {
+            start: Some(start),
+            end: Some(end),
+            ..
+        }) = higher::Range::hir(expr)
+        {
+            check_for_parens(cx, start, true);
+            check_for_parens(cx, end, false);
         }
     }
 }

tests/ui/needless_parens_on_range_literal.fixed

@@ -6,4 +6,7 @@
 
 fn main() {
     let _ = 'a'..='z';
+    let _ = 'a'..='z';
+    let _ = (1.)..2.;
+    let _ = (1.)..2.;
 }

tests/ui/needless_parens_on_range_literal.rs

@@ -6,4 +6,7 @@
 
 fn main() {
     let _ = ('a')..=('z');
+    let _ = 'a'..='z';
+    let _ = (1.)..2.;
+    let _ = (1.)..(2.);
 }

tests/ui/needless_parens_on_range_literal.stderr

@@ -12,5 +12,11 @@ error: needless parenthesis on range literal can be removed
 LL |     let _ = ('a')..=('z');
    |                     ^^^^^ help: try: `'z'`
 
-error: aborting due to 2 previous errors
+error: needless parenthesis on range literal can be removed
+  --> $DIR/needless_parens_on_range_literal.rs:11:19
+   |
+LL |     let _ = (1.)..(2.);
+   |                   ^^^^ help: try: `2.`
+
+error: aborting due to 3 previous errors