forked from glen/fostr
feat: Initial statix assignment of types to expressions
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@ -27,9 +27,9 @@ for path in TEST_LIST:
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if pfm: continue # skip examples that don't parse
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ntfm = re.search(r'\n\s*\]\].*?don.t.test', details)
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if ntfm: continue # explicit skip
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em = re.search(r'\n\s*\]\]', details)
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em = re.search(r'\n\]\]', details)
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if not em: continue
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example = details[:em.start()+1]
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example = details[:em.start()+1].replace('[[','').replace(']]','')
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expath = destdir / f"{name}.{EXT}"
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expath.write_text(example)
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echo Wrote @(expath)
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@ -22,3 +22,4 @@ menus
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action: "Show pre-analyzed AST" = debug-show-pre-analyzed (source)
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action: "Show analyzed AST" = debug-show-analyzed
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action: "Show analyzed type" = debug-show-type
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@ -1,6 +1,16 @@
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module basic
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language fostr
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test hw1_type [[
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[[stream]] << [['Hello, world!']]
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]]
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run get-type on #1 to STREAM()
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run get-type on #2 to STRING()
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run get-type to STREAM()
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/** writes
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Hello, world!**/
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/** md
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Title: A whirlwind tour of fostr
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@ -1,5 +1,14 @@
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module analysis
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signature
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sorts
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TYPE
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constructors
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INT : TYPE
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STRING : TYPE
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STREAM : TYPE
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imports
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statixruntime
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@ -51,3 +60,18 @@ rules // Debugging
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debug-show-analyzed: (sel, _, _, path, projp) -> (filename, result)
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with filename := <guarantee-extension(|"analyzed.aterm")> path
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; result := sel
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// Extract the type assigned to a node by Statix
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get-type: node -> type
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where
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// Assigns variable a to be the result of the Statix analysis of the entire program (or throws an error)
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a := <stx-get-ast-analysis <+ fail-msg(|$[no analysis on node [<strip-annos;write-to-string> node]])>;
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// Gets the type of the given node (or throws an error)
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type := <stx-get-ast-type(|a) <+ fail-msg(|$[no type on node [<strip-annos;write-to-string> node]])> node
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fail-msg(|msg) = err-msg(|$[get-type: [msg]]); fail
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// Prints the analyzed type of a selection.
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debug-show-type: (sel, _, _, path, projp) -> (filename, result)
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with filename := <guarantee-extension(|"type.aterm")> path
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; result := <get-type> sel
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@ -25,17 +25,18 @@ to be "OK" from the point of view of Statix:
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Then I reached the point at which the grammar was basically just
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```SDF3
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// Start.TopLevel = <Ex>
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// Ex.Sequence = sq:Ex+ {layout: align-list sq}
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// Start.TopLevel = <Seq>
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// Seq = <Ex>
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// Seq.Sequence = sq:Ex+ {layout(align-list sq)}
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// Ex.Terminated = <<Ex>;>
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{! "\git docs/statix_start:syntax/fostr.sdf3" extract:
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start: TermEx.Terminate
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stop: (.*bracket.*)
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!}
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```
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(The first three clauses are in comments because they approximate fostr's
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(The first four clauses are in comments because they approximate fostr's
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grammar; it actually uses a few more sorts for sequences of
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expressions, to acheive fostr's exact layout rules.)
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expressions, to achieve fostr's exact layout rules.)
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This was the first point at which there were two different types that might
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need to be written to standard output (Int and String), and although of course
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@ -46,15 +47,158 @@ that point since I knew it would be hopeless without statically typing fostr
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programs).
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So it was time to bite the bullet and add type checking via Statix to fostr.
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The first step is to replace the simple assertion that any TopLevel
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is OK with a constraint that its Seq must type properly, and an assignment of
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that type to the top level node:
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```statix
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programOk(tl@TopLevel(seq)) :- {T}
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type_Seq(seq) == T,
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@tl.type := T.
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```
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Of course, for this to even parse, we must have a definition of `type_Seq`:
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```statix
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**/
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/** md */
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signature
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sorts TYPE // semantic type
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constructors
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INT : TYPE
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STRING : TYPE
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STREAM : TYPE
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/* **/
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// see docs/implementation.md for detail on how to switch to multi-file analysis
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rules // single-file entry point
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programOk : Start
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programOk(TopLevel(_)).
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/** md
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rules
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type_Seq : Seq -> TYPE
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```
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**/
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type_LineSeq : LineSeq -> TYPE
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programOk(tl@TopLevel(seq)) :- {T}
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type_LineSeq(seq) == T,
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@tl.type := T.
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/** md
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Now to type a Seq, we look to the syntax, and see that there are two
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possibilities for what it might be: just an Ex, or a Sequence(_) of a
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list of 'Ex's. For the first, Statix does not allow one sort to simply
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"become" another, but the Spoofax infrastructure automatically inserts
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"injection" constructors for us, in this case one named Ex2Seq. So the
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first rule for `type_Seq` is straightforward:
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```statix
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type_Seq(s@Ex2Seq(e)) = T : -
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type_Ex(e) == T,
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@s.type := T.
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```
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where of course type_Ex needs its own declaration analogous to the above.
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**/
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type_Line : Line -> TYPE
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type_LineSeq(ls@Line2LineSeq(l)) = T :-
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type_Line(l) == T,
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@ls.type := T.
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type_OptTermEx : OptTermEx -> TYPE
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type_Line(l@OptTermEx2Line(ote)) = T :-
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type_OptTermEx(ote) == T,
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@l.type := T.
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type_Ex : Ex -> TYPE
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type_OptTermEx(ote@Ex2OptTermEx(e)) = T :-
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type_Ex(e) == T,
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@ote.type :=T.
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/** md
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This brings us to the syntax rules for the basic expressions themselves,
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which comprise almost all of the remaining fostr language constructs.
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But first a mechanism suggested by Ivo Wilms to avoid repeating the node
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type annotation in every rule:
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```statix
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**/
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/** md */
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ty_Ex : Ex -> TYPE
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type_Ex(e) = ty@ty_Ex(e) :-
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@e.type := ty.
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/* **/
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/** md
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```
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At this stage in fostr's development, there was no difference between a
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terminated and unterminated expression, so the typing rule for that
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constructor was trivial:
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```statix
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ty_Ex(Terminated(e)) = ty_Ex(e).
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```
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**/
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type_TermEx: TermEx -> TYPE
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type_TermEx(te@Terminate(e)) = T :-
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type_Ex(e) == T,
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@te.type := T.
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/** md
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Now typing literals is straightforward:
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```statix
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**/
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/** md */
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ty_Ex(Int(_)) = INT().
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ty_Ex(LitString(_)) = STRING().
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ty_Ex(e@Stream()) = STREAM().
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/* **/
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/** md
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```
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Finally we get to the binary operators, and here we use the pattern found in
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recent versions of the
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"[chicago](https://github.com/MetaBorgCube/statix-sandbox/tree/master/chicago)"
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example language and in the Fall 2020 TU-Delft class lecture on
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[Name Binding and Name Resolution](https://tudelft-cs4200-2020.github.io/lectures/2020/09/24/lecture5/).
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This pattern lets us specify error messages.
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```statix
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**/
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/** md */
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ty_Ex(Sum(e1, e2)) = INT() :-
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type_Ex(e1) == INT() | error $[Expression [e1] not an Int in sum.]@e1,
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type_Ex(e2) == INT() | error $[Expression [e2] not an Int in sum.]@e2.
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ty_Ex(Gets(e1, e2)) = STREAM() :- {T}
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type_Ex(e1) == STREAM() | error $[Only Streams may receive items.]@e1,
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type_Ex(e2) == T.
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ty_Ex(To(e1, e2)) = T :-
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type_Ex(e1) == T,
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type_Ex(e2) == STREAM() | error $[Items may only be sent to Streams.]@e2.
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/* **/
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/** md
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```
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### Using type annotations in transformation
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_Probably want to include stuff from analysis.str/ haskell.str here_
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**/
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rules // multi-file entry point
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