Auto merge of rust-lang#12168 - y21:issue12159, r=blyxyas

[`default_numeric_fallback`]: improve const context detection

Fixes rust-lang#12159

The lint didn't actually recognize any of the associated consts (in the linked issue), because in those cases the parent is an `ImplItem` and not an `Item`, but it only actually emitted a lint for i32 and f64 because the other cases failed the very last check here
https://github.com/rust-lang/rust-clippy/blob/bb2d4973648b1af18d7ba6a3028ed7c92fde07fb/clippy_lints/src/default_numeric_fallback.rs#L91-L96

A better check for detecting constness would be using `body_const_context`, which is what this PR does.

changelog: [`default_numeric_fallback`]: recognize associated consts

clippy_lints/src/default_numeric_fallback.rs

@@ -1,10 +1,10 @@
 use clippy_utils::diagnostics::span_lint_hir_and_then;
+use clippy_utils::numeric_literal;
 use clippy_utils::source::snippet_opt;
-use clippy_utils::{get_parent_node, numeric_literal};
 use rustc_ast::ast::{LitFloatType, LitIntType, LitKind};
 use rustc_errors::Applicability;
 use rustc_hir::intravisit::{walk_expr, walk_stmt, Visitor};
-use rustc_hir::{Block, Body, Expr, ExprKind, FnRetTy, HirId, ItemKind, Lit, Node, Stmt, StmtKind};
+use rustc_hir::{Block, Body, ConstContext, Expr, ExprKind, FnRetTy, HirId, Lit, Stmt, StmtKind};
 use rustc_lint::{LateContext, LateLintPass, LintContext};
 use rustc_middle::lint::in_external_macro;
 use rustc_middle::ty::{self, FloatTy, IntTy, PolyFnSig, Ty};
@@ -50,11 +50,11 @@ declare_lint_pass!(DefaultNumericFallback => [DEFAULT_NUMERIC_FALLBACK]);
 
 impl<'tcx> LateLintPass<'tcx> for DefaultNumericFallback {
     fn check_body(&mut self, cx: &LateContext<'tcx>, body: &'tcx Body<'_>) {
-        let is_parent_const = if let Some(Node::Item(item)) = get_parent_node(cx.tcx, body.id().hir_id) {
-            matches!(item.kind, ItemKind::Const(..))
-        } else {
-            false
-        };
+        let hir = cx.tcx.hir();
+        let is_parent_const = matches!(
+            hir.body_const_context(hir.body_owner_def_id(body.id())),
+            Some(ConstContext::Const { inline: false } | ConstContext::Static(_))
+        );
         let mut visitor = NumericFallbackVisitor::new(cx, is_parent_const);
         visitor.visit_body(body);
     }

tests/ui/default_numeric_fallback_i32.fixed

@@ -216,4 +216,44 @@ mod type_already_inferred {
     }
 }
 
+mod issue12159 {
+    #![allow(non_upper_case_globals, clippy::exhaustive_structs)]
+    pub struct Foo;
+
+    static F: i32 = 1;
+    impl Foo {
+        const LIFE_u8: u8 = 42;
+        const LIFE_i8: i8 = 42;
+        const LIFE_u16: u16 = 42;
+        const LIFE_i16: i16 = 42;
+        const LIFE_u32: u32 = 42;
+        const LIFE_i32: i32 = 42;
+        const LIFE_u64: u64 = 42;
+        const LIFE_i64: i64 = 42;
+        const LIFE_u128: u128 = 42;
+        const LIFE_i128: i128 = 42;
+        const LIFE_usize: usize = 42;
+        const LIFE_isize: isize = 42;
+        const LIFE_f32: f32 = 42.;
+        const LIFE_f64: f64 = 42.;
+
+        const fn consts() {
+            const LIFE_u8: u8 = 42;
+            const LIFE_i8: i8 = 42;
+            const LIFE_u16: u16 = 42;
+            const LIFE_i16: i16 = 42;
+            const LIFE_u32: u32 = 42;
+            const LIFE_i32: i32 = 42;
+            const LIFE_u64: u64 = 42;
+            const LIFE_i64: i64 = 42;
+            const LIFE_u128: u128 = 42;
+            const LIFE_i128: i128 = 42;
+            const LIFE_usize: usize = 42;
+            const LIFE_isize: isize = 42;
+            const LIFE_f32: f32 = 42.;
+            const LIFE_f64: f64 = 42.;
+        }
+    }
+}
+
 fn main() {}

tests/ui/default_numeric_fallback_i32.rs

@@ -216,4 +216,44 @@ mod type_already_inferred {
     }
 }
 
+mod issue12159 {
+    #![allow(non_upper_case_globals, clippy::exhaustive_structs)]
+    pub struct Foo;
+
+    static F: i32 = 1;
+    impl Foo {
+        const LIFE_u8: u8 = 42;
+        const LIFE_i8: i8 = 42;
+        const LIFE_u16: u16 = 42;
+        const LIFE_i16: i16 = 42;
+        const LIFE_u32: u32 = 42;
+        const LIFE_i32: i32 = 42;
+        const LIFE_u64: u64 = 42;
+        const LIFE_i64: i64 = 42;
+        const LIFE_u128: u128 = 42;
+        const LIFE_i128: i128 = 42;
+        const LIFE_usize: usize = 42;
+        const LIFE_isize: isize = 42;
+        const LIFE_f32: f32 = 42.;
+        const LIFE_f64: f64 = 42.;
+
+        const fn consts() {
+            const LIFE_u8: u8 = 42;
+            const LIFE_i8: i8 = 42;
+            const LIFE_u16: u16 = 42;
+            const LIFE_i16: i16 = 42;
+            const LIFE_u32: u32 = 42;
+            const LIFE_i32: i32 = 42;
+            const LIFE_u64: u64 = 42;
+            const LIFE_i64: i64 = 42;
+            const LIFE_u128: u128 = 42;
+            const LIFE_i128: i128 = 42;
+            const LIFE_usize: usize = 42;
+            const LIFE_isize: isize = 42;
+            const LIFE_f32: f32 = 42.;
+            const LIFE_f64: f64 = 42.;
+        }
+    }
+}
+
 fn main() {}