Auto merge of rust-lang#8729 - Serial-ATA:issue-7318, r=Manishearth

Fix missing whitespace in `collapsible_else_if` suggestion

changelog: Fix missing whitespace in [`collapsible_else_if`] suggestion
closes rust-lang#7318

Author: bors

clippy_lints/src/collapsible_if.rs

@@ -13,13 +13,14 @@
 //! This lint is **warn** by default
 
 use clippy_utils::diagnostics::{span_lint_and_sugg, span_lint_and_then};
-use clippy_utils::source::{snippet_block, snippet_block_with_applicability};
+use clippy_utils::source::{snippet, snippet_block, snippet_block_with_applicability};
 use clippy_utils::sugg::Sugg;
 use if_chain::if_chain;
 use rustc_ast::ast;
 use rustc_errors::Applicability;
 use rustc_lint::{EarlyContext, EarlyLintPass};
 use rustc_session::{declare_lint_pass, declare_tool_lint};
+use rustc_span::Span;
 
 declare_clippy_lint! {
     /// ### What it does
@@ -102,7 +103,7 @@ impl EarlyLintPass for CollapsibleIf {
 fn check_if(cx: &EarlyContext<'_>, expr: &ast::Expr) {
     if let ast::ExprKind::If(check, then, else_) = &expr.kind {
         if let Some(else_) = else_ {
-            check_collapsible_maybe_if_let(cx, else_);
+            check_collapsible_maybe_if_let(cx, then.span, else_);
         } else if let ast::ExprKind::Let(..) = check.kind {
             // Prevent triggering on `if let a = b { if c { .. } }`.
         } else {
@@ -119,7 +120,7 @@ fn block_starts_with_comment(cx: &EarlyContext<'_>, expr: &ast::Block) -> bool {
     trimmed_block_text.starts_with("//") || trimmed_block_text.starts_with("/*")
 }
 
-fn check_collapsible_maybe_if_let(cx: &EarlyContext<'_>, else_: &ast::Expr) {
+fn check_collapsible_maybe_if_let(cx: &EarlyContext<'_>, then_span: Span, else_: &ast::Expr) {
     if_chain! {
         if let ast::ExprKind::Block(ref block, _) = else_.kind;
         if !block_starts_with_comment(cx, block);
@@ -128,14 +129,23 @@ fn check_collapsible_maybe_if_let(cx: &EarlyContext<'_>, else_: &ast::Expr) {
         if !else_.span.from_expansion();
         if let ast::ExprKind::If(..) = else_.kind;
         then {
+            // Prevent "elseif"
+            // Check that the "else" is followed by whitespace
+            let up_to_else = then_span.between(block.span);
+            let requires_space = if let Some(c) = snippet(cx, up_to_else, "..").chars().last() { !c.is_whitespace() } else { false };
+
             let mut applicability = Applicability::MachineApplicable;
             span_lint_and_sugg(
                 cx,
                 COLLAPSIBLE_ELSE_IF,
                 block.span,
                 "this `else { if .. }` block can be collapsed",
                 "collapse nested if block",
-                snippet_block_with_applicability(cx, else_.span, "..", Some(block.span), &mut applicability).into_owned(),
+                format!(
+                    "{}{}",
+                    if requires_space { " " } else { "" },
+                    snippet_block_with_applicability(cx, else_.span, "..", Some(block.span), &mut applicability)
+                ),
                 applicability,
             );
         }

tests/ui/collapsible_else_if.fixed

@@ -75,3 +75,10 @@ fn main() {
         }
     }
 }
+
+#[rustfmt::skip]
+#[allow(dead_code)]
+fn issue_7318() {
+    if true { println!("I've been resolved!")
+    }else if false {}
+}

tests/ui/collapsible_else_if.rs

@@ -89,3 +89,12 @@ fn main() {
         }
     }
 }
+
+#[rustfmt::skip]
+#[allow(dead_code)]
+fn issue_7318() {
+    if true { println!("I've been resolved!")
+    }else{
+        if false {}
+    }
+}

tests/ui/collapsible_else_if.stderr

@@ -150,5 +150,14 @@ LL +         println!("!")
 LL +     }
    |
 
-error: aborting due to 7 previous errors
+error: this `else { if .. }` block can be collapsed
+  --> $DIR/collapsible_else_if.rs:97:10
+   |
+LL |       }else{
+   |  __________^
+LL | |         if false {}
+LL | |     }
+   | |_____^ help: collapse nested if block: `if false {}`
+
+error: aborting due to 8 previous errors