Add an overlap checker to ISLE

cranelift/isle/isle/Cargo.toml

@@ -11,12 +11,14 @@ version = "0.89.0"
 [dependencies]
 log = { version = "0.4", optional = true }
 miette = { version = "5.1.0", optional = true }
+rayon = "^1.5"
 
 [dev-dependencies]
 tempfile = "3"
 
 [features]
 default = []
 
+overlap-errors = []
 logging = ["log"]
 miette-errors = ["miette"]

cranelift/isle/isle/src/compile.rs

@@ -7,6 +7,7 @@ use crate::{ast, codegen, sema, trie};
 pub fn compile(defs: &ast::Defs, options: &codegen::CodegenOptions) -> Result<String> {
     let mut typeenv = sema::TypeEnv::from_ast(defs)?;
     let termenv = sema::TermEnv::from_ast(&mut typeenv, defs)?;
+    crate::overlap::check(&mut typeenv, &termenv)?;
     let tries = trie::build_tries(&typeenv, &termenv);
     Ok(codegen::codegen(&typeenv, &termenv, &tries, options))
 }

cranelift/isle/isle/src/error.rs

@@ -42,6 +42,17 @@ pub enum Error {
         span: Span,
     },
 
+    /// The rules mentioned overlap in the input they accept.
+    OverlapError {
+        /// The error message.
+        msg: String,
+
+        /// The locations of all the rules that overlap. When there are more than two rules
+        /// present, the first rule is the one with the most overlaps (likely a fall-through
+        /// wildcard case).
+        rules: Vec<(Source, Span)>,
+    },
+
     /// Multiple errors.
     Errors(Vec<Error>),
 }
@@ -108,6 +119,10 @@ impl std::fmt::Display for Error {
             #[cfg(feature = "miette-errors")]
             Error::TypeError { msg, .. } => write!(f, "type error: {}", msg),
 
+            Error::OverlapError { msg, rules, .. } => {
+                writeln!(f, "overlap error: {}\n{}", msg, OverlappingRules(&rules))
+            }
+
             Error::Errors(_) => write!(
                 f,
                 "found {} errors:\n\n{}",
@@ -128,6 +143,16 @@ impl std::fmt::Display for DisplayErrors<'_> {
     }
 }
 
+struct OverlappingRules<'a>(&'a [(Source, Span)]);
+impl std::fmt::Display for OverlappingRules<'_> {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        for (src, span) in self.0 {
+            writeln!(f, "  {}", span.from.pretty_print_with_filename(&*src.name))?;
+        }
+        Ok(())
+    }
+}
+
 /// A source file and its contents.
 #[derive(Clone)]
 pub struct Source {

cranelift/isle/isle/src/lib.rs

@@ -98,6 +98,7 @@ pub mod error;
 pub mod ir;
 pub mod lexer;
 mod log;
+pub mod overlap;
 pub mod parser;
 pub mod sema;
 pub mod trie;