Make extern routines survive analysis.

src/sixtypical/analyzer.py

@@ -115,6 +115,9 @@ def analyze_program(program):
 
 def analyze_routine(routine, routines):
     assert isinstance(routine, Routine)
+    if routine.block is None:
+        # it's an extern, that's fine
+        return
     context = Context(routine.inputs, routine.outputs, routine.trashes)
     analyze_block(routine.block, context, routines)
     for ref in routine.outputs:

src/sixtypical/compiler.py

@@ -26,8 +26,9 @@ def compile_program(program, emitter):
 def compile_routine(routine, emitter, routines):
     assert isinstance(routine, Routine)
     label = emitter.make_label(routine.name)
-    compile_block(routine.block, emitter, routines)
-    emitter.emit(RTS())
+    if routine.block:
+        compile_block(routine.block, emitter, routines)
+        emitter.emit(RTS())
     return label
 
 
@@ -97,7 +98,7 @@ def compile_instr(instr, emitter, routines):
     elif opcode == 'shr':
         raise NotImplementedError
     elif opcode == 'call':
-        raise NotImplementedError
+        raise NotImplementedError(instr.name)
     elif opcode == 'if':
         raise NotImplementedError
     else:

src/sixtypical/parser.py

@@ -194,7 +194,7 @@ class Parser(object):
             self.scanner.scan()
             dest = self.locexpr()
             return Instr(opcode=opcode, dest=dest, src=None)
-        elif self.scanner.token in ("call"):
+        elif self.scanner.token in ("call",):
             opcode = self.scanner.token
             self.scanner.scan()
             name = self.scanner.token

tests/SixtyPical Analysis.md

@@ -663,6 +663,48 @@ calling it.
     | }
     ? UninitializedAccessError: x
 
+Calling an extern is just the same as calling a defined routine with the
+same constraints.
+
+    | routine chrout
+    |   inputs a
+    |   trashes a
+    |   @ 65490
+    | 
+    | routine main
+    |   trashes a, z, n
+    | {
+    |     ld a, 65
+    |     call chrout
+    | }
+    = ok
+
+    | routine chrout
+    |   inputs a
+    |   trashes a
+    |   @ 65490
+    | 
+    | routine main
+    |   trashes a, z, n
+    | {
+    |     call chrout
+    | }
+    ? UninitializedAccessError: a
+
+    | routine chrout
+    |   inputs a
+    |   trashes a
+    |   @ 65490
+    | 
+    | routine main
+    |   trashes a, x, z, n
+    | {
+    |     ld a, 65
+    |     call chrout
+    |     ld x, a
+    | }
+    ? UninitializedAccessError: a
+
 ### if ###
 
 Both blocks of an `if` are analyzed.

tests/SixtyPical Compilation.md

@@ -39,8 +39,7 @@ Call extern.
     | 
     | routine main
     |   inputs a
-    |   outputs a
-    |   trashes c, z, n, v
+    |   trashes a, z, n
     | {
     |     ld a, 65
     |     call chrout