[mlir][shape] Extend shape.cstr_require with a message.

[silvas]

Summary

I realized when using this that one can't get very good error messages
without an additional message attribute.

[silvas]

fix typo

[frgossen]

Thanks

mlir/include/mlir/Dialect/Shape/IR/ShapeOps.td

def Shape_ConstWitnessOp : Shape_Op<"const_witness", [ConstantLike, NoSideEffect]> {
   let assemblyFormat = "$passing attr-dict";
 
   let hasFolder = 1;
 }
 
 def Shape_CstrRequireOp : Shape_Op<"cstr_require", []> {
   let summary = "Represents a runtime assertion that an i1 is `true`";
   let description = [{
-    Represents a runtime assretion that an i1 is true. It returns a
+    Represents a runtime assertion that an i1 is true. It returns a
     !shape.witness to order this assertion.
 
     For simplicity, prefer using other cstr_* ops if they are available for a
     given constraint.
 
     Example:
     ```mlir
     %bool = ...
-    %w0 = shape.cstr_require %bool // Passing if `%bool` is true.
+    %w0 = shape.cstr_require %bool, "msg" // Passing if `%bool` is true.
     ```
+
+    Since this op can be used to express many different possible assertions
+    (depending on whatever computation calculated `pred`), the `msg`
+    should clarify the nature of the assertion for users.
   }];
-  let arguments = (ins I1:$pred);
+  let arguments = (ins I1:$pred, StrAttr:$msg);
   let results = (outs Shape_WitnessType:$result);
 
-  let assemblyFormat = "$pred attr-dict";
+  let assemblyFormat = "$pred `,` $msg attr-dict";
 
   let hasFolder = 1;
 }
 
 #endif // SHAPE_OPS

mlir/test/Dialect/Shape/canonicalize.mlir

 // -----
 // cstr_require with constant can be folded
 // CHECK-LABEL: func @cstr_require_fold
 func @cstr_require_fold() {
   // CHECK-NEXT: shape.const_witness true
   // CHECK-NEXT: consume.witness
   // CHECK-NEXT: return
   %true = constant true
-  %0 = shape.cstr_require %true
+  %0 = shape.cstr_require %true, "msg"
   "consume.witness"(%0) : (!shape.witness) -> ()
   return
 }
 
 // -----
 // cstr_require without constant cannot be folded
 // CHECK-LABEL: func @cstr_require_no_fold
 func @cstr_require_no_fold(%arg0: i1) {
   // CHECK-NEXT: shape.cstr_require
   // CHECK-NEXT: consume.witness
   // CHECK-NEXT: return
-  %0 = shape.cstr_require %arg0
+  %0 = shape.cstr_require %arg0, "msg"
   "consume.witness"(%0) : (!shape.witness) -> ()
   return
 }
 
 // -----
 // assuming_all with known passing witnesses can be folded
 // CHECK-LABEL: func @f
 func @f() {

mlir/test/Dialect/Shape/ops.mlir

 func @test_constraints() {
   %0 = shape.const_shape [] : !shape.shape
   %1 = shape.const_shape [1, 2, 3] : !shape.shape
   %true = constant true
   %w0 = shape.cstr_broadcastable %0, %1 : !shape.shape, !shape.shape
   %w1 = shape.cstr_eq %0, %1
   %w2 = shape.const_witness true
   %w3 = shape.const_witness false
-  %w4 = shape.cstr_require %true
+  %w4 = shape.cstr_require %true, "msg"
   %w_all = shape.assuming_all %w0, %w1, %w2, %w3, %w4
   shape.assuming %w_all -> !shape.shape {
     %2 = "shape.any"(%0, %1) : (!shape.shape, !shape.shape) -> !shape.shape
     shape.assuming_yield %2 : !shape.shape
   }
   return
 }