feat: Allow indented continuation lines

Resolves #2.

bin/extract_tests.xsh

@@ -23,6 +23,8 @@ for path in TEST_LIST:
   tests = re.split(r'test\s*(.+?)\s*\[\[.*?\n', contents)[1:]
   testit = iter(tests)
   for name, details in zip(testit, testit):
+    pfm = re.search(r'\n\s*\]\].*?parse\s*fails', details)
+    if pfm: continue # skip examples that don't parse
     em = re.search(r'\n\s*\]\]', details)
     if not em: continue
     example = details[:em.start()+1]

editor/Syntax.esv

@@ -8,7 +8,7 @@ imports
 language
 
   table         : target/metaborg/sdf.tbl
-  start symbols : Ex
+  start symbols : Start
 
   line comment  : "//"
   block comment : "/*" * "*/"

syntax/fostr.sdf3

@@ -6,14 +6,16 @@ imports
 
 context-free start-symbols
   
-  Ex
+  Start
 
 context-free sorts
 
-  Ex
+  Start Ex
 
 context-free syntax
   
+  Start.TopLevel = prog:Ex {layout(offside prog)}
+
   Ex.Int      = INT
   Ex.Stdio    = <stdio>
   Ex.Sum      = {Ex "+"}+

tests/basic.spt

@@ -14,7 +14,8 @@ that writes the sum of the ASCII codes for 'H', 'W', and '!' to standard output:
 
 /** md */ test emit_sum [[
 stdio << 72 + 87 + 33
-]]/* **/ parse to Receives(Stdio(), Sum([Int("72"), Int("87"), Int("33")]))
+]]/* **/ parse to TopLevel(Receives(Stdio(),
+                                    Sum([Int("72"), Int("87"), Int("33")])))
 /** writes
 192**/
 
@@ -62,9 +63,9 @@ left-associative, so that way we can chain insertions into a stream:
 
 /** md */ test emit_twice [[
 stdio << 72 + 87 + 33 << 291
-]]/* **/ parse to Receives(
-  Receives(Stdio(), Sum([Int("72"), Int("87"), Int("33")])),
-  Int("291"))
+]]/* **/ parse to TopLevel(
+  Receives(Receives(Stdio(), Sum([Int("72"), Int("87"), Int("33")])),
+           Int("291")))
 /** writes
 192291**/
 
@@ -80,25 +81,48 @@ with `>>`; both forms return the first argument:
 
 /** md */ test enters_twice [[
 (7 + 8 >> stdio + 9) >> stdio
-]]/* **/ parse to
-  Enters(Sum([Int("7"), Enters(Int("8"), Stdio()), Int("9")]), Stdio())
+]]/* **/ parse to TopLevel(
+  Enters(Sum([Int("7"), Enters(Int("8"), Stdio()), Int("9")]), Stdio()))
 /** writes
 824**/
 
+/** md
+```
+
+### Layout in fostr
+
+Expressions may be laid out onto multiple lines, as long as all continuation
+lines are indented from the start of the initial line:
+```fostr
+**/
+
+/** md */ test receive_enter_break [[
+stdio <<
+  7
+  + 8 >> stdio
+  + 9
+]]/* **/ parse to TopLevel(
+  Receives(Stdio(), Sum([Int("7"), Enters(Int("8"), Stdio()), Int("9")])))
+/** writes
+824**/
+
+/** md
+```
+(So for example you will get a parse error with something like this:)
+```fostr
+**/
+
+/** md */ test enter_receive_bad_break [[
+(7 + 8 >> stdio + 9)
+>> (stdio << 9 + 2)
+]] /* **/ parse fails
+
 /* Extra tests not in the tour */
-
-test receive_enter [[
-stdio << (7 + 8 >> stdio + 9)
-]]/* **/ parse to
-  Receives(Stdio(), Sum([Int("7"), Enters(Int("8"), Stdio()), Int("9")]))
-/** writes
-824**/
-
 test enter_receive [[
 (7 + 8 >> stdio + 9) >> (stdio << 9 + 2)
-]]/* **/ parse to
+]]/* **/ parse to TopLevel(
   Enters(Sum([Int("7"),Enters(Int("8"),Stdio()),Int("9")]),
-         Receives(Stdio(),Sum([Int("9"),Int("2")])))
+         Receives(Stdio(),Sum([Int("9"),Int("2")]))))
 /** writes
 81124**/
 

trans/analysis.str

@@ -19,8 +19,8 @@ rules // Analysis
   // multi-file analysis
 //  editor-analyze = stx-editor-analyze(pre-analyze, post-analyze|"statics", "projectOk", "fileOk")
 
-  pre-analyze  = origin-track-forced(explicate-injections-fostr-Ex)
-  post-analyze = origin-track-forced(implicate-injections-fostr-Ex)
+  pre-analyze  = origin-track-forced(explicate-injections-fostr-Start)
+  post-analyze = origin-track-forced(implicate-injections-fostr-Start)
 
 rules // Editor Services
 

trans/haskell.str

@@ -42,8 +42,8 @@ rules
   brack: x -> $<[<x>]>
 
 strategies
-  // wrap expression in a toplevel and then apply code generation
-  haskell = !TopLevel(<id>); bottomup(try(hs <+ hslist))
+
+  haskell = bottomup(try(hs <+ hslist))
 
   // Interface haskell code generation with editor services and file system
   to-haskell: (selected, _, _, path, project-path) -> (filename, result)

trans/javascript.str

@@ -24,8 +24,8 @@ rules
   jslist: x -> $<[<<join(|", ")>x>]>
 
 strategies
-  // wrap expression in a toplevel, then generate code from bottom up
-  javascript = !TopLevel(<id>); bottomup(try(js <+ jslist))
+
+  javascript = bottomup(try(js <+ jslist))
 
   // Interface javascript code generation with editor services and file system
   to-javascript: (selected, _, _, path, project-path) -> (filename, result)

trans/python.str

@@ -28,8 +28,7 @@ rules
 
 strategies
 
-  // wrap with a toplevel, then generate code from the bottom up
-  python = !TopLevel(<id>); bottomup(try(py <+ pylist))
+  python = bottomup(try(py <+ pylist))
 
   // Interface python code generation with editor services and file system
   to-python: (selected, _, _, path, project-path) -> (filename, result)

trans/statics.stx

@@ -6,11 +6,9 @@ imports signatures/fostr-sig
 
 rules // single-file entry point
 
-  programOk : Ex
+  programOk : Start
 
-  programOk(Sum(_)).
-  programOk(Receives(_,_)).
-  programOk(Enters(_,_)).
+  programOk(TopLevel(_)).
 
 rules // multi-file entry point
 
@@ -18,6 +16,6 @@ rules // multi-file entry point
 
   projectOk(s).
 
-  fileOk : scope * Ex
+  fileOk : scope * Start
 
-  fileOk(s, Receives(_,_)).
+  fileOk(s, TopLevel(_)).