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-rw-r--r--crates/cfg/src/lib.rs17
1 files changed, 16 insertions, 1 deletions
diff --git a/crates/cfg/src/lib.rs b/crates/cfg/src/lib.rs
index 03b8dd767..916d39a0b 100644
--- a/crates/cfg/src/lib.rs
+++ b/crates/cfg/src/lib.rs
@@ -1,4 +1,4 @@
1//! cfg defines conditional compiling options, `cfg` attibute parser and evaluator 1//! cfg defines conditional compiling options, `cfg` attribute parser and evaluator
2 2
3mod cfg_expr; 3mod cfg_expr;
4mod dnf; 4mod dnf;
@@ -52,6 +52,7 @@ impl CfgOptions {
52 } 52 }
53} 53}
54 54
55#[derive(Clone, Debug, PartialEq, Eq)]
55pub struct CfgDiff { 56pub struct CfgDiff {
56 // Invariants: No duplicates, no atom that's both in `enable` and `disable`. 57 // Invariants: No duplicates, no atom that's both in `enable` and `disable`.
57 enable: Vec<CfgAtom>, 58 enable: Vec<CfgAtom>,
@@ -59,6 +60,20 @@ pub struct CfgDiff {
59} 60}
60 61
61impl CfgDiff { 62impl CfgDiff {
63 /// Create a new CfgDiff. Will return None if the same item appears more than once in the set
64 /// of both.
65 pub fn new(enable: Vec<CfgAtom>, disable: Vec<CfgAtom>) -> Option<CfgDiff> {
66 let mut occupied = FxHashSet::default();
67 for item in enable.iter().chain(disable.iter()) {
68 if !occupied.insert(item) {
69 // was present
70 return None;
71 }
72 }
73
74 Some(CfgDiff { enable, disable })
75 }
76
62 /// Returns the total number of atoms changed by this diff. 77 /// Returns the total number of atoms changed by this diff.
63 pub fn len(&self) -> usize { 78 pub fn len(&self) -> usize {
64 self.enable.len() + self.disable.len() 79 self.enable.len() + self.disable.len()