Implement lint logic.

Author: xiongmao86

clippy_lints/src/utils/internal_lints.rs

@@ -1,6 +1,6 @@
 use crate::utils::{
     is_expn_of, match_def_path, match_type, method_calls, paths, span_lint, span_lint_and_help, span_lint_and_sugg,
-    walk_ptrs_ty,
+    walk_ptrs_ty, snippet_opt
 };
 use if_chain::if_chain;
 use rustc::hir::map::Map;
@@ -404,8 +404,108 @@ fn is_trigger_fn(fn_kind: FnKind<'_>) -> bool {
 
 declare_lint_pass!(CollapsibleCalls => [COLLAPSIBLE_SPAN_LINT_CALLS]);
 
-impl EarlyLintPass for CollapsibleCalls {
+impl  EarlyLintPass for CollapsibleCalls {
     fn check_expr(&mut self, cx: &EarlyContext<'_>, expr: &ast::Expr) {
-        span_lint_and_help(cx, COLLAPSIBLE_SPAN_LINT_CALLS, expr.span, "lint_message", "help_message");
+        use ast::ExprKind;
+
+        if_chain! {
+            if let ExprKind::Call(ref func, ref and_then_args) = expr.kind;
+            if let ExprKind::Path(None, ref path) = func.kind;
+            if let match_path_ast(path, &["span_lint_and_then"]);
+            if and_then_args.len() == 5;
+            if let ExprKind::Closure(_, _, _, _, block) = and_then_args[4].kind;
+            if let ExprKind::Block(block, _) = block.kind;
+            let stmts = block.stmts;
+            if stmts.len() == 1;
+            if let StmtKind::Expr(only_expr) = stmts[0].kind;
+            if let ExprKind::MethodCall(ps, span_call_args) = only_expr.kind;
+            then {
+                let cx_snippet = snippet(cx, and_then_args[0].span);
+                let lint_snippet= snippet(cx, and_then_args[1].span);
+                let span_snippet = snippet(cx, and_then_args[2].span);
+                let msg_snippet= snippet(cx, and_then_args[3].span);
+
+                match ps.ident.name.as_str() {
+                    "span_suggestion" => {
+                        let span_snippet_of_span_call = snippet(cx, span_call_args[0].span);
+                        let help_snippet = snippet(cx, span_call_args[1].span);
+                        let sugg_snippet = snippet(cx, span_call_args[2].span);
+                        let applicability_snippet = snippet(cx, span_call_args[3].span);
+
+                        if span_snippet == span_snippet_of_span_call {
+                            span_lint_and_sugg (
+                                cx,
+                                COLLAPSIBLE_SPAN_LINT_CALLS,
+                                expr.span,
+                                "this call is collapsible",
+                                "collapse into",
+                                format!(
+                                    "span_lint_and_sugg({}, {}, {}, {}, {}, {},{})",
+                                    cx_snippet,
+                                    lint_snippet,
+                                    span_snippet,
+                                    msg_snippet,
+                                    help_snippet,
+                                    sugg_snippet,
+                                    applicability_snippet
+                                ),
+                                Applicability::MachineApplicable
+                            );
+                        }
+                    },
+                    "span_help" => {
+                        let span_snippet_of_span_call = snippet(cx, span_call_args[0].span);
+                        let help_snippet = snippet(cx, span_call_args[1].span);
+
+                        if span_snippet == span_snippet_of_span_call {
+                            span_lint_and_sugg(
+                                cx,
+                                COLLAPSIBLE_SPAN_LINT_CALLS,
+                                expr.span,
+                                "this call is collapsible",
+                                "collapse into",
+                                format!(
+                                    "span_lint_and_help({}, {}, {}, {},{})",
+                                    cx_snippet,
+                                    lint_snippet,
+                                    span_snippet,
+                                    msg_snippet,
+                                    help_snippet
+                                ),
+                                Applicability::MachineApplicable
+                            );
+                        }
+                    },
+                    "span_note" => {
+                        let span_snippet_of_span_call = snippet(cx, span_call_args[0].span);
+                        let note_snippet = snippet(cx, span_call_args[1].span);
+
+                        if span_snippet == span_snippet_of_span_call {
+                            span_lint_and_sugg(
+                                cx,
+                                COLLAPSIBLE_SPAN_LINT_CALLS,
+                                expr.span,
+                                "this call is collspible",
+                                "collapse into",
+                                format!(
+                                    "span_lint_and_note({},{}, {}, {}, {})",
+                                    cx_snippet,
+                                    lint_snippet,
+                                    span_snippet,
+                                    msg_snippet,
+                                    note_snippet
+                                ),
+                                Applicability::MachineApplicable
+                            );
+                        }
+                    },
+                    _  => (),
+                }
+            }
+        }
     }
-}
+}
+
+fn snippet(cx: &EarlyContext<'_>, span: Span) -> String {
+    snippet_opt(cx, span).expect("should be able to retrive span.")
+}