Auto merge of #4406 - lzutao:fix-assert-const, r=phansch

Fix assertions on const lint

Replaces #4402
changelog: none

clippy_lints/src/assertions_on_constants.rs

@@ -1,11 +1,9 @@
-use if_chain::if_chain;
 use rustc::hir::{Expr, ExprKind};
 use rustc::lint::{LateContext, LateLintPass, LintArray, LintPass};
 use rustc::{declare_lint_pass, declare_tool_lint};
-use syntax_pos::Span;
 
 use crate::consts::{constant, Constant};
-use crate::utils::{in_macro_or_desugar, is_direct_expn_of, span_help_and_lint};
+use crate::utils::{in_macro_or_desugar, is_direct_expn_of, is_expn_of, span_help_and_lint};
 
 declare_clippy_lint! {
     /// **What it does:** Checks for `assert!(true)` and `assert!(false)` calls.
@@ -33,42 +31,39 @@ declare_lint_pass!(AssertionsOnConstants => [ASSERTIONS_ON_CONSTANTS]);
 
 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for AssertionsOnConstants {
     fn check_expr(&mut self, cx: &LateContext<'a, 'tcx>, e: &'tcx Expr) {
-        let mut is_debug_assert = false;
-        let debug_assert_not_in_macro_or_desugar = |span: Span| {
-            is_debug_assert = true;
-            // Check that `debug_assert!` itself is not inside a macro
-            !in_macro_or_desugar(span)
-        };
-        if_chain! {
-            if let Some(assert_span) = is_direct_expn_of(e.span, "assert");
-            if !in_macro_or_desugar(assert_span)
-                || is_direct_expn_of(assert_span, "debug_assert")
-                    .map_or(false, debug_assert_not_in_macro_or_desugar);
-            if let ExprKind::Unary(_, ref lit) = e.node;
-            if let Some(bool_const) = constant(cx, cx.tables, lit);
-            then {
-                match bool_const.0 {
-                    Constant::Bool(true) => {
+        let lint_assert_cb = |is_debug_assert: bool| {
+            if let ExprKind::Unary(_, ref lit) = e.node {
+                if let Some((Constant::Bool(is_true), _)) = constant(cx, cx.tables, lit) {
+                    if is_true {
                         span_help_and_lint(
                             cx,
                             ASSERTIONS_ON_CONSTANTS,
                             e.span,
                             "`assert!(true)` will be optimized out by the compiler",
-                            "remove it"
+                            "remove it",
                         );
-                    },
-                    Constant::Bool(false) if !is_debug_assert => {
+                    } else if !is_debug_assert {
                         span_help_and_lint(
                             cx,
                             ASSERTIONS_ON_CONSTANTS,
                             e.span,
                             "`assert!(false)` should probably be replaced",
-                            "use `panic!()` or `unreachable!()`"
+                            "use `panic!()` or `unreachable!()`",
                         );
-                    },
-                    _ => (),
+                    }
                 }
             }
+        };
+        if let Some(debug_assert_span) = is_expn_of(e.span, "debug_assert") {
+            if in_macro_or_desugar(debug_assert_span) {
+                return;
+            }
+            lint_assert_cb(true);
+        } else if let Some(assert_span) = is_direct_expn_of(e.span, "assert") {
+            if in_macro_or_desugar(assert_span) {
+                return;
+            }
+            lint_assert_cb(false);
         }
     }
 }