Add some failing tests for analyzing "for".

src/sixtypical/analyzer.py

@@ -1,6 +1,6 @@
 # encoding: UTF-8
 
-from sixtypical.ast import Program, Routine, Block, Instr, SingleOp, If, Repeat, WithInterruptsOff
+from sixtypical.ast import Program, Routine, Block, Instr, SingleOp, If, Repeat, For, WithInterruptsOff
 from sixtypical.model import (
     TYPE_BYTE, TYPE_WORD,
     TableType, BufferType, PointerType, VectorType, RoutineType,
@@ -329,6 +329,8 @@ class Analyzer(object):
             self.analyze_if(instr, context)
         elif isinstance(instr, Repeat):
             self.analyze_repeat(instr, context)
+        elif isinstance(instr, For):
+            self.analyze_for(instr, context)
         elif isinstance(instr, WithInterruptsOff):
             self.analyze_block(instr.block, context)
         else:
@@ -611,3 +613,12 @@ class Analyzer(object):
         self.analyze_block(instr.block, context)
         if instr.src is not None:
             context.assert_meaningful(instr.src)
+
+    def analyze_for(self, instr, context):
+        # TODO: find the range of the loop variable in context, make sure it fits
+
+        # TODO: set the loop variable as 'not writeable' in the context
+
+        self.analyze_block(instr.block, context)
+
+        # TODO: at the end of the loop, we know the new range of the loop variable

tests/SixtyPical Analysis.md

@@ -1659,6 +1659,56 @@ The body of `repeat forever` can be empty.
     | }
     = ok
 
+### for ###
+
+Basic "open-faced for" loop.  We'll start with the "upto" variant.
+
+In a "for" loop, we know the exact range the loop variable takes on.
+
+    | byte table[16] tab
+    | 
+    | define foo routine inputs tab trashes a, x, c, z, v, n {
+    |     ld x, 0
+    |     for x upto 15 {
+    |         ld a, tab + x
+    |     }
+    | }
+    = ok
+
+    | byte table[15] tab
+    | 
+    | define foo routine inputs tab trashes a, x, c, z, v, n {
+    |     ld x, 0
+    |     for x upto 15 {
+    |         ld a, tab + x
+    |     }
+    | }
+    ? RangeExceededError
+
+You cannot modify the loop variable in a "for" loop.
+
+    | byte table[16] tab
+    | 
+    | define foo routine inputs tab trashes a, x, c, z, v, n {
+    |     ld x, 0
+    |     for x upto 15 {
+    |         ld x, 0
+    |     }
+    | }
+    ? ForbiddenWriteError
+
+If the range isn't known to be smaller than the final value, you can't go up to it.
+
+    | byte table[32] tab
+    | 
+    | define foo routine inputs tab trashes a, x, c, z, v, n {
+    |     ld x, 16
+    |     for x upto 15 {
+    |         ld a, tab + x
+    |     }
+    | }
+    ? RangeExceededError
+
 ### copy ###
 
 Can't `copy` from a memory location that isn't initialized.