Course examples: unimplemented features preventing transpilation

[associate-1]

Summary

Transpiling the 16 example programs in kroc/modules/course/examples/ reveals that 11 out of 16 fail to parse due to unimplemented language features. Only hello_world.occ, hello_seq_world.occ, hello_raw_world.occ, echoing.occ, and double_echo.occ transpile successfully.

This is a tracking issue for the full set of missing features discovered. Some have their own dedicated issues.

Unimplemented Features

Standard occam features

Feature	Description	Affected files	Issue	Status
INLINE FUNCTION	Function qualifier INT INLINE FUNCTION f(...)	bar.occ	#44	Done
ALT replicators	ALT i = 0 FOR n (like SEQ/PAR/IF replicators)	sort_pump.occ, sort_pump_2.occ, sort_inside.occ, sort_inside_2.occ, bar.occ	#45	Done
INT16/INT32/INT64	Extended integer width types	cast.occ, casting.occ, commstime.occ	#46	Done
tim ? AFTER expr	Timer AFTER input (wait until time)	bar.occ, demo.occ, sort_inside_2.occ	#60	Done
PRI ALT	Prioritised alternation	bar.occ	#84	Parsed (no true priority semantics)
Guarded ALT (&)	(condition) & chan ? x boolean pre-conditions	bar.occ	#67	Done
Multi-value CASE labels	'*n', '*c' comma-separated case values	test_bell.occ	#61	Done
[][]TYPE / [][n]TYPE	Multi-dimensional array declarations	bar.occ, test_utils.occ	#64	[n][m] and [][] done; [][n] remaining
Expression-sized arrays	[expr]TYPE with non-literal sizes	various	#62	Done
Dotted protocol tags	bar.blank, bar.terminate in PROTOCOL CASE	bar.occ		Done
*" string escape	Escaped quote character inside string literals	test_utils.occ	#65	Open

occam-pi extensions

Feature	Description	Affected files	Issue	Status
SHARED CHAN / CLAIM	Shared channels and exclusive access blocks	bar.occ	#40	Deferred
MOBILE types	Dynamically allocated mobile data	demo.occ	#40	Deferred

Error distribution by file

File	Root causes
bar.occ	INLINE, PRI ALT, ALT replicator, AFTER, SHARED/CLAIM, guarded ALT, [][n] arrays, dotted protocol tags
cast.occ	INT16/INT32/INT64
casting.occ	INT16/INT32/INT64
commstime.occ	INT64
demo.occ	AFTER, MOBILE
sort_inside.occ	ALT replicator, multi-dim arrays
sort_inside_2.occ	ALT replicator, AFTER
sort_pump.occ	ALT replicator
sort_pump_2.occ	ALT replicator
test_bell.occ	Multi-value CASE labels
test_utils.occ	[][n] arrays, string escape

[associate-1]

Status Update (2026-02-22)

Since this issue was opened, three features have been implemented:

• INLINE FUNCTION (Support INLINE function modifier #44, closed)
• ALT replicators (Support ALT replicators #45, closed)
• INT16/INT32/INT64 (Support INT16, INT32, INT64 integer types #46, closed)

Current results: 10/16 transpile, 6/16 pass go vet

File	Transpile	go vet	Remaining blockers
hello_world.occ	OK	OK	—
hello_seq_world.occ	OK	OK	—
hello_raw_world.occ	OK	OK	—
echoing.occ	OK	OK	—
double_echo.occ	OK	OK	—
commstime.occ	OK	OK	— (was blocked by INT64)
cast.occ	OK	FAIL	BOOL↔BYTE type conversion (byte(bool) invalid in Go); ROUND/TRUNC qualifiers on type casts
casting.occ	OK	FAIL	Same as cast.occ
sort_pump.occ	OK	FAIL	VAL BYTE x IS 1: abbreviation inferred as int instead of byte, causing INT→BYTE assignment error
sort_pump_2.occ	OK	FAIL	Same as sort_pump.occ
bar.occ	FAIL	—	PRI ALT, SHARED/CLAIM, dotted protocol tags, tim ? AFTER, multi-dim arrays, guarded ALT with boolean expressions
demo.occ	FAIL	—	tim ? AFTER, MOBILE types
sort_inside.occ	FAIL	—	Expression-sized arrays ([max.delay]BYTE, [total - 1]BYTE) — not multi-dim arrays as originally reported
sort_inside_2.occ	FAIL	—	SIZE of direction-annotated channel name (SIZE monitor?), tim ? AFTER
test_bell.occ	FAIL	—	Multi-value CASE labels ('*n', '*c')
test_utils.occ	FAIL	—	Multi-dim arrays ([][2]BYTE), *" string escape

Summary of changes since original report

• Files now fully working: commstime.occ (1 new, 6 total)
• Files now transpiling but with codegen bugs: cast.occ, casting.occ, sort_pump.occ, sort_pump_2.occ (4 new)
• Files still failing to parse: 6 (down from 11)

Corrections to original error distribution

• sort_inside.occ: Root cause is expression-sized arrays ([expr]TYPE), not multi-dim arrays or ALT replicators. ALT replicators are now implemented and are not used in this file.
• sort_inside_2.occ: ALT replicator itself works, but SIZE monitor? (SIZE of a direction-annotated channel param) fails to parse. Also blocked by tim ? AFTER.

New codegen bugs discovered

1. BOOL↔BYTE conversion: Go does not allow byte(boolVal). Needs a conditional expression or helper. Also BOOL(expr) type conversion is unhandled.
2. ROUND/TRUNC qualifiers: REAL32 ROUND expr and INT64 TRUNC expr are not implemented — the qualifier is currently parsed as a separate function call.
3. Typed abbreviation inference: VAL BYTE first.col IS 1: generates first_col := 1 (inferred as int), should generate var first_col byte = 1 to preserve the declared type.

Remaining unimplemented features (updated)

Feature	Affected files
tim ? AFTER expr	bar.occ, demo.occ, sort_inside_2.occ
PRI ALT	bar.occ
Guarded ALT with boolean expr (cond) & chan ? x	bar.occ
SHARED CHAN / CLAIM	bar.occ
MOBILE types	demo.occ
Multi-value CASE labels	test_bell.occ
Multi-dim arrays ([][n]TYPE)	bar.occ, test_utils.occ
Expression-sized arrays ([expr]TYPE)	sort_inside.occ
Dotted protocol tags	bar.occ
*" string escape	test_utils.occ
SIZE of direction-annotated name	sort_inside_2.occ
ROUND/TRUNC cast qualifiers	cast.occ, casting.occ
BOOL↔BYTE type conversions	cast.occ, casting.occ
Typed abbreviation type preservation	sort_pump.occ, sort_pump_2.occ

[associate-1]

Status Update (2026-02-22) — After PRs #53, #54, and typed abbreviation fix

Three codegen bugs from the previous update have been fixed:

• ROUND/TRUNC qualifiers (Support ROUND/TRUNC qualifiers on type conversions #54, merged) — REAL32 ROUND i16, INT64 TRUNC r32, etc. now generate correctly
• BOOL↔numeric type conversions (Fix BOOL↔BYTE/numeric type conversions #53, merged) — BOOL expr → ((expr) != 0), INT boolExpr → _boolToInt(expr)
• Typed abbreviation type loss (Fix typed abbreviations losing declared type #55) — VAL BYTE first.col IS 1: now emits var first_col byte = 1 instead of first_col := 1

Current results: 10/16 transpile, 7/16 pass go vet

File	Transpile	go vet	Remaining blockers
hello_world.occ	OK	OK	—
hello_seq_world.occ	OK	OK	—
hello_raw_world.occ	OK	OK	—
echoing.occ	OK	OK	—
double_echo.occ	OK	OK	—
commstime.occ	OK	OK	—
cast.occ	OK	FAIL	boolVars scoping bug — #56
casting.occ	OK	FAIL	Same as cast.occ — #56
sort_pump.occ	OK	FAIL	Channel array direction covariance — #57
sort_pump_2.occ	OK	FAIL	Same as sort_pump.occ — #57
bar.occ	FAIL	—	PRI ALT, SHARED/CLAIM, dotted protocol tags, tim ? AFTER, guarded ALT, multi-dim arrays
demo.occ	FAIL	—	tim ? AFTER, MOBILE
sort_inside.occ	FAIL	—	Expression-sized arrays ([expr]TYPE)
sort_inside_2.occ	FAIL	—	SIZE monitor?, tim ? AFTER
test_bell.occ	FAIL	—	Multi-value CASE labels
test_utils.occ	FAIL	—	Multi-dim arrays ([][n]TYPE), *" string escape

Changes from previous update

• Newly passing go vet: commstime.occ was already passing; no new files pass vet this round, but previous failures were replaced by different, previously-hidden failures
• ROUND/TRUNC: fixed — no longer a blocker for cast.occ/casting.occ
• Typed abbreviation type loss: fixed — no longer a blocker for sort_pump.occ/sort_pump_2.occ
• New bugs uncovered: 2 (filed as boolVars map is global: name collisions cause invalid Go code #56 and Channel array slices incompatible with direction-restricted params #57)

Remaining codegen bugs

Bug	Affected files	Issue
boolVars map is global/flat — name collisions across scopes	cast.occ, casting.occ	#56
[]chan T cannot be passed as []<-chan T in Go (slice covariance)	sort_pump.occ, sort_pump_2.occ	#57

Remaining unimplemented features (unchanged)

Feature	Affected files
tim ? AFTER expr	bar.occ, demo.occ, sort_inside_2.occ
PRI ALT	bar.occ
Guarded ALT ((cond) & chan ? x)	bar.occ
SHARED CHAN / CLAIM	bar.occ
MOBILE types	demo.occ
Multi-value CASE labels	test_bell.occ
Multi-dim arrays ([][n]TYPE)	bar.occ, test_utils.occ
Expression-sized arrays ([expr]TYPE)	sort_inside.occ
Dotted protocol tags	bar.occ
*" string escape	test_utils.occ
SIZE of direction-annotated name	sort_inside_2.occ

[associate-1]

Status Update — After PRs #55, #56, #57, #58

Four codegen bugs have been fixed since the last update:

• boolVars scoping (boolVars map is global: name collisions cause invalid Go code #56, closed) — scoped per proc/function body to prevent cross-proc leakage
• Channel array direction covariance (Channel array slices incompatible with direction-restricted params #57, closed via fix/chan-array-dir-params) — direction dropped from []CHAN OF TYPE params since Go slices are invariant
• Typed abbreviation type loss (Fix typed abbreviations losing declared type #55, closed) — already noted in previous update
• boolVars per-proc scoping (Fix: scope boolVars per proc/function body #58, merged) — related follow-up to boolVars map is global: name collisions cause invalid Go code #56

Current results: 10/16 transpile, 10/16 pass go vet

File	Transpile	go vet	Remaining blockers
hello_world.occ	OK	OK	—
hello_seq_world.occ	OK	OK	—
hello_raw_world.occ	OK	OK	—
echoing.occ	OK	OK	—
double_echo.occ	OK	OK	—
commstime.occ	OK	OK	—
cast.occ	OK	OK	— (was blocked by boolVars scoping)
casting.occ	OK	OK	— (was blocked by boolVars scoping)
sort_pump.occ	OK	OK	— (was blocked by chan array direction)
sort_pump_2.occ	OK	OK	— (was blocked by chan array direction)
bar.occ	FAIL	—	PRI ALT, SHARED/CLAIM, dotted protocol tags, tim ? AFTER, guarded ALT, multi-dim arrays
demo.occ	FAIL	—	tim ? AFTER, MOBILE
sort_inside.occ	FAIL	—	Expression-sized arrays ([expr]TYPE)
sort_inside_2.occ	FAIL	—	SIZE monitor?, tim ? AFTER
test_bell.occ	FAIL	—	Multi-value CASE labels
test_utils.occ	FAIL	—	Multi-dim arrays ([][n]TYPE), *" string escape

Changes from previous update

• Newly passing go vet: cast.occ, casting.occ, sort_pump.occ, sort_pump_2.occ (4 new, 10 total)
• All codegen bugs from the previous update are resolved — no files transpile but fail vet
• Still failing to parse: 6 files (unchanged from previous update)

Progress since issue was opened

Milestone	Transpile	go vet
Original report	5/16	5/16
After #44, #45, #46	10/16	6/16
After #53, #54, #55	10/16	7/16
Current (after #56, #57, #58)	10/16	10/16

Remaining work — new issues filed

The remaining 6 files are all blocked at parse time by unimplemented language features. Individual issues have been filed, with estimated difficulty:

Feature	Affected files	Difficulty	Issue
tim ? AFTER expr	bar.occ, demo.occ, sort_inside_2.occ	Medium — parser, AST, and codegen changes across timer input handling	#60
Multi-value CASE labels	test_bell.occ	Easy — extend case label parsing to accept comma-separated values	#61
Expression-sized arrays ([expr]TYPE)	sort_inside.occ	Medium — parser must accept expressions as array sizes; codegen must emit make() for non-literal sizes	#62
SIZE of direction-annotated name	sort_inside_2.occ	Easy — strip trailing ?/! direction suffix when parsing SIZE operand	#63
Multi-dimensional arrays ([][n]TYPE)	bar.occ, test_utils.occ	Medium — parser, AST, and codegen must all support nested array dimensions	#64
*" string escape	test_utils.occ	Easy — small addition to existing escape sequence handling in the lexer	#65
PRI ALT	bar.occ	Medium — new keyword, AST flag, and codegen strategy (Go select has no native priority)	#66
Guarded ALT with boolean conditions	bar.occ	Medium — parser must handle expr & prefix on ALT cases; codegen must conditionally enable/disable select cases	#67
Dotted protocol tags	bar.occ	Easy — allow dotted identifiers in protocol tag positions; goIdent() already converts dots to underscores	#68

SHARED/CLAIM and MOBILE are tracked in #40 (hard — significant language extension).

Suggested implementation order

Easiest wins first, maximizing files unblocked per effort:

1. Support multi-value CASE labels #61 (multi-value CASE) — easy, unblocks test_bell.occ
2. Support *" string escape sequence #65 (*" escape) + Support multi-dimensional arrays ([][n]TYPE) #64 (multi-dim arrays) — unblocks test_utils.occ
3. Support SIZE of direction-annotated channel name #63 (SIZE direction) + Support timer AFTER input (tim ? AFTER expr) #60 (timer AFTER) — unblocks sort_inside_2.occ and demo.occ
4. Support expression-sized array declarations #62 (expression-sized arrays) — unblocks sort_inside.occ
5. Support dotted protocol tags (e.g., bar.data) #68 (dotted tags) + Support guarded ALT with boolean pre-conditions #67 (guarded ALT) + Support PRI ALT (prioritised alternation) #66 (PRI ALT) + Support KRoC mobile/shared channel extensions #40 (SHARED/CLAIM/MOBILE) — chipping away at bar.occ