(and ...) combinator in patterns

cranelift/isle/TODO

@@ -1,4 +1,3 @@
-- `and` combinator in input.
 - inputs to external extractors? "polarity" of args?
 - "extractor macros" rather than full rule reversal? (rule ...) and (pattern ...)?
 - Document semantics carefully, especially wrt extractors.

cranelift/isle/isle_examples/test4.isle

@@ -0,0 +1,17 @@
+(type u32 (primitive u32))
+(type A (enum (A1 (x u32))))
+
+(decl Ext1 (u32) A)
+(decl Ext2 (u32) A)
+(extractor Ext1 ext1)
+(extractor Ext2 ext2)
+
+(decl Lower (A) A)
+
+(rule
+  (Lower
+    (and
+      a
+      (Ext1 x)
+      (Ext2 =x)))
+  a)

cranelift/isle/src/ast.rs

@@ -83,6 +83,8 @@ pub enum Pattern {
     Term { sym: Ident, args: Vec<Pattern> },
     /// An operator that matches anything.
     Wildcard,
+    /// N sub-patterns that must all match.
+    And { subpats: Vec<Pattern> },
 }
 
 /// An expression: the right-hand side of a rule.

cranelift/isle/src/ir.rs

@@ -253,6 +253,13 @@ impl PatternSequence {
                     }
                 }
             }
+            &Pattern::And(_ty, ref children) => {
+                let input = input.unwrap();
+                for child in children {
+                    self.gen_pattern(Some(input), typeenv, termenv, child, vars);
+                }
+                None
+            }
             &Pattern::Wildcard(_ty) => {
                 // Nothing!
                 None

cranelift/isle/src/parser.rs

@@ -305,13 +305,23 @@ impl<'a> Parser<'a> {
             }
         } else if self.is_lparen() {
             self.lparen()?;
-            let sym = self.parse_ident()?;
-            let mut args = vec![];
-            while !self.is_rparen() {
-                args.push(self.parse_pattern()?);
+            if self.is_sym_str("and") {
+                self.symbol()?;
+                let mut subpats = vec![];
+                while !self.is_rparen() {
+                    subpats.push(self.parse_pattern()?);
+                }
+                self.rparen()?;
+                Ok(Pattern::And { subpats })
+            } else {
+                let sym = self.parse_ident()?;
+                let mut args = vec![];
+                while !self.is_rparen() {
+                    args.push(self.parse_pattern()?);
+                }
+                self.rparen()?;
+                Ok(Pattern::Term { sym, args })
             }
-            self.rparen()?;
-            Ok(Pattern::Term { sym, args })
         } else {
             Err(self.error(pos.unwrap(), "Unexpected pattern".into()))
         }

cranelift/isle/src/sema.rs

@@ -123,6 +123,7 @@ pub enum Pattern {
     ConstInt(TypeId, i64),
     Term(TypeId, TermId, Vec<Pattern>),
     Wildcard(TypeId),
+    And(TypeId, Vec<Pattern>),
 }
 
 #[derive(Clone, Debug, PartialEq, Eq)]
@@ -141,6 +142,7 @@ impl Pattern {
             &Self::ConstInt(t, ..) => t,
             &Self::Term(t, ..) => t,
             &Self::Wildcard(t, ..) => t,
+            &Self::And(t, ..) => t,
         }
     }
 }
@@ -293,11 +295,13 @@ impl TypeEnv {
     }
 }
 
+#[derive(Clone)]
 struct Bindings {
     next_var: usize,
     vars: Vec<BoundVar>,
 }
 
+#[derive(Clone)]
 struct BoundVar {
     name: Sym,
     id: VarId,
@@ -548,6 +552,21 @@ impl TermEnv {
                 })?;
                 Ok((Pattern::Wildcard(ty), ty))
             }
+            &ast::Pattern::And { ref subpats } => {
+                let mut expected_ty = expected_ty;
+                let mut children = vec![];
+                for subpat in subpats {
+                    let (subpat, ty) =
+                        self.translate_pattern(tyenv, pos, &*subpat, expected_ty, bindings)?;
+                    expected_ty = expected_ty.or(Some(ty));
+                    children.push(subpat);
+                }
+                if expected_ty.is_none() {
+                    return Err(tyenv.error(pos, "No type for (and ...) form.".to_string()));
+                }
+                let ty = expected_ty.unwrap();
+                Ok((Pattern::And(ty, children), ty))
+            }
             &ast::Pattern::BindPattern {
                 ref var,
                 ref subpat,