float_cmp: Change allow_named_constants to an allow list.

Author: Jarcho

clippy_config/src/conf.rs

@@ -657,7 +657,7 @@ define_Conf! {
     ///     x == VALUE
     /// }
     /// ```
-    (float_cmp_ignore_named_constants: bool = true),
+    (float_cmp_allowed_constants: Vec<String> = true),
     /// Lint: FLOAT_CMP
     ///
     /// Whether to ignore comparisons which have a constant result.

clippy_lints/src/operators/mod.rs

@@ -24,6 +24,8 @@ mod verbose_bit_mask;
 pub(crate) mod arithmetic_side_effects;
 
 use clippy_config::Conf;
+use clippy_utils::def_path_def_ids;
+use rustc_hir::def_id::DefIdSet;
 use rustc_hir::{Body, Expr, ExprKind, UnOp};
 use rustc_lint::{LateContext, LateLintPass};
 use rustc_session::impl_lint_pass;
@@ -774,9 +776,8 @@ declare_clippy_lint! {
     "explicit self-assignment"
 }
 
-#[derive(Clone, Copy)]
 struct FloatCmpConfig {
-    ignore_named_constants: bool,
+    allowed_constants: DefIdSet,
     ignore_constant_comparisons: bool,
     ignore_change_detection: bool,
 }
@@ -794,7 +795,11 @@ impl Operators {
             verbose_bit_mask_threshold: conf.verbose_bit_mask_threshold,
             modulo_arithmetic_allow_comparison_to_zero: conf.allow_comparison_to_zero,
             float_cmp_config: FloatCmpConfig {
-                ignore_named_constants: conf.float_cmp_ignore_named_constants,
+                allowed_constants: conf
+                    .float_cmp_allowed_constants
+                    .iter()
+                    .flat_map(|x| def_path_def_ids(tcx, &x.split("::").collect::<Vec<_>>()))
+                    .collect(),
                 ignore_constant_comparisons: conf.float_cmp_ignore_constant_comparisons,
                 ignore_change_detection: conf.float_cmp_ignore_change_detection,
             },