Implement expressions #290

felix-oq · 2023-04-25T13:23:33Z

Preparation for #213, implementation of RFC 0009

Introduces new operators, type inference and evaluation semantics for expressions. Also includes options for lazy and exhaustive evaluation (affects binary boolean operators so they don't necessarily evaluate both sub-expressions).

In many cases, the code for type inference is pretty much the same per operator, except for some special cases (e.g. different treatment of decimal and integer and that operands of ==/!= need to have the same type). I'm not sure how to properly refactor the code, so both usual and special cases can be covered conveniently. Introducing a sub-type relationship between integer and decimal or an implicit conversion mechanism could already help to generally cope with the first special case. Let me know if you have further ideas, maybe we can discuss that in a call.

The prior redundancy in the evaluation was mostly eliminated in 02f05bd by introducing evaluator classes that implement shared evaluation logic. A similar refactoring for type inference also address the problem described above.

Known issue:

Sometimes, when using symbolic operators without surrounding spaces, a lexer error occurs:

Not sure why that is the case (probably due to the grammar?). I fiddled around with it a bit but didn't find an immediate solution for the problem.

Includes the comparison of numeric and text values.

libs/language-server/src/lib/ast/expressions/operators/binary-arithmetic-expression.ts

libs/language-server/src/lib/validation/checks/property-assignment.ts

libs/language-server/src/lib/ast/expressions/operator-evaluator.ts

georg-schwarz

Good job on the refactoring!

From a code review perspective it looks good to me, but can't guarantee that I was able to catch all bugs (esp. because the feature is quite large). I feel like we should start introducing tests soon with the increasing logic.

rhazn

Sick 👍

libs/execution/src/lib/constraints/executors/allowlist-constraint-executor.ts

rhazn · 2023-04-27T16:07:02Z

libs/extensions/std/lang/src/text-file-interpreter-meta-inf.ts

@@ -25,18 +26,16 @@ export class TextFileInterpreterMetaInformation extends BlockMetaInformation {
          },
          validation: (property, context) => {
            const propertyValue = property.value;
-            assert(isTextLiteral(propertyValue));
+            assert(isExpression(propertyValue));


This seems to be repeated quite a bit, might be good to have a util method to get property values of a specific type. I.e. evaluatedPropertyExpression<T> (in this case evaluatedPropertyExpression<string> that reads the property, evaluates the expression, asserts the type and returns the correctly typed result.

libs/language-server/src/lib/ast/model-util.ts

felix-oq added 8 commits April 20, 2023 13:22

Allow more operators in boolean expressions

e700727

Includes the comparison of numeric and text values.

Implement arithmetic operators

54df1c3

Add options for lazy and exhaustive expression evaluation

ddb042e

Add workaround for unescaped division operator in monarch

93261cb

Update Langium CLI to the latest version

96064d9

Introduce registry for operators

93c19b0

Extract method for common error message generation

dde9493

Improve condition for simplification

63632bf

felix-oq marked this pull request as ready for review April 26, 2023 08:30

felix-oq requested review from rhazn and georg-schwarz April 26, 2023 08:30