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fix ordering bug in pattern exhaustiveness

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Folkert 2020-04-23 20:12:40 +02:00 • committed by Richard Feldman
parent f8b540b6f4
commit dc320e9fd9
3 changed files with 109 additions and 6 deletions
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19
compiler/mono/src/pattern.rs
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@ -346,6 +346,7 @@ fn is_useful(matrix: &PatternMatrix, vector: &Row) -> bool {
// rows that match the same things. This is not a useful vector!
false
} else {
// NOTE: if there are bugs in this code, look at the ordering of the row/matrix
let mut vector = vector.clone();
let first_pattern = vector.remove(0);
let patterns = vector;
@ -359,8 +360,8 @@ fn is_useful(matrix: &PatternMatrix, vector: &Row) -> bool {
.collect();
let mut new_row = Vec::new();
new_row.extend(args);
new_row.extend(patterns);
new_row.extend(args);
is_useful(&new_matrix, &new_row)
}
@ -450,13 +451,21 @@ fn specialize_row_by_literal(literal: &Literal, row: &Row) -> Option<Row> {
let patterns = row;
match head {
Some(Literal(lit)) => if &lit == literal { Some(patterns) } else{ None } ,
Some(Literal(lit)) => {
if &lit == literal {
Some(patterns)
} else {
None
}
}
Some(Anything) => Some(patterns),
Some(Ctor(_,_,_)) => panic!( "Compiler bug! After type checking, constructors and literals should never align in pattern match exhaustiveness checks."),
Some(Ctor(_, _, _)) => panic!(
r#"Compiler bug! After type checking, constructors and literals should never align in pattern match exhaustiveness checks."#
),
None => panic!("Compiler error! Empty matrices should not get specialized."),
}
None => panic!("Compiler error! Empty matrices should not get specialized."),
}
}
/// INVARIANT: (length row == N) ==> (length result == N-1)