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better parse errors

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This commit is contained in:
John Alanbrook
2026-02-10 06:51:26 -06:00
parent 3f7e34cd7a
commit 747227de40
3 changed files with 255 additions and 1 deletions
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2
docs/language.md
View File

@@ -11,7 +11,7 @@ type: "docs"
### Variables and Constants
Variables are declared with `var`, constants with `def`. All declarations must be initialized and must appear at the function body level — not inside `if`, `while`, `for`, or bare `{}` blocks.
Variables are declared with `var`, constants with `def`. All declarations must be initialized and must appear at the function body level — not inside `if`, `while`, `for`, or `do` blocks.
```javascript
var x = 10

89
parse.cm
View File

@@ -9,6 +9,9 @@ var parse = function(tokens, src, filename, tokenizer) {
var tok = null
var got_lf = false
var prev_tok = null
var _control_depth = 0
var _control_type = null
var _expecting_body = false
var advance = function() {
var t = null
@@ -176,6 +179,9 @@ var parse = function(tokens, src, filename, tokenizer) {
var sub_ast = null
var sub_stmt = null
var sub_expr = null
var meth_old_cd = 0
var meth_old_ct = null
var meth_old_eb = false
if (k == "number") {
node = ast_node("number", start)
@@ -399,6 +405,12 @@ var parse = function(tokens, src, filename, tokenizer) {
else if (tok.kind == "eof") parse_error(tok, "unterminated method parameter list")
if (length(params) > 4) parse_error(tok, "functions cannot have more than 4 parameters")
fn.arity = length(params)
meth_old_cd = _control_depth
meth_old_ct = _control_type
meth_old_eb = _expecting_body
_control_depth = 0
_control_type = null
_expecting_body = false
if (tok.kind == "{") {
advance()
fn.statements = parse_block_statements()
@@ -407,6 +419,9 @@ var parse = function(tokens, src, filename, tokenizer) {
} else {
parse_error(tok, "expected '{' for method body")
}
_control_depth = meth_old_cd
_control_type = meth_old_ct
_expecting_body = meth_old_eb
fn.function_nr = function_nr
function_nr = function_nr + 1
ast_node_end(fn)
@@ -788,6 +803,9 @@ var parse = function(tokens, src, filename, tokenizer) {
var prev_names = null
var pname = null
var old_dis = 0
var old_cd = _control_depth
var old_ct = _control_type
var old_eb = _expecting_body
if (in_disruption) {
parse_error(tok, "cannot define function inside disruption clause")
@@ -834,6 +852,9 @@ var parse = function(tokens, src, filename, tokenizer) {
if (length(params) > 4) parse_error(tok, "functions cannot have more than 4 parameters")
node.arity = length(params)
_control_depth = 0
_control_type = null
_expecting_body = false
if (tok.kind == "{") {
advance()
stmts = parse_block_statements()
@@ -859,6 +880,9 @@ var parse = function(tokens, src, filename, tokenizer) {
}
}
_control_depth = old_cd
_control_type = old_ct
_expecting_body = old_eb
node.function_nr = function_nr
function_nr = function_nr + 1
ast_node_end(node)
@@ -875,6 +899,9 @@ var parse = function(tokens, src, filename, tokenizer) {
var expr = null
var prev_names = null
var pname = null
var old_cd = _control_depth
var old_ct = _control_type
var old_eb = _expecting_body
node.arrow = true
if (in_disruption) {
@@ -925,6 +952,9 @@ var parse = function(tokens, src, filename, tokenizer) {
advance()
}
_control_depth = 0
_control_type = null
_expecting_body = false
if (tok.kind == "{") {
advance()
stmts = parse_block_statements()
@@ -940,6 +970,9 @@ var parse = function(tokens, src, filename, tokenizer) {
node.statements = stmts
}
_control_depth = old_cd
_control_type = old_ct
_expecting_body = old_eb
node.function_nr = function_nr
function_nr = function_nr + 1
ast_node_end(node)
@@ -971,8 +1004,25 @@ var parse = function(tokens, src, filename, tokenizer) {
var elif = null
var p1_tok = null
var labeled_stmt = null
var depth = 0
var saved_ct = null
var saved_cd = 0
var saved_eb = false
if (k == "{") {
if (!_expecting_body) {
parse_error(start, "bare block '{ ... }' is not a valid statement; use a function, if, while, or for instead")
advance()
depth = 1
while (tok.kind != "eof" && depth > 0) {
if (tok.kind == "{") depth = depth + 1
else if (tok.kind == "}") depth = depth - 1
if (depth > 0) advance()
}
if (tok.kind == "}") advance()
return null
}
_expecting_body = false
node = ast_node("block", start)
advance()
stmts = parse_block_statements()
@@ -983,6 +1033,9 @@ var parse = function(tokens, src, filename, tokenizer) {
}
if (k == "var" || k == "def") {
if (_control_depth > 0) {
parse_error(start, "'" + k + "' declarations must appear at function body level, not inside '" + _control_type + "'; move this declaration before the '" + _control_type + "' statement")
}
kind_name = k
is_def = (k == "def")
advance()
@@ -1009,6 +1062,8 @@ var parse = function(tokens, src, filename, tokenizer) {
}
} else if (is_def) {
parse_error(start, "missing initializer for constant '" + var_name + "'")
} else {
parse_error(start, "'var' declarations must be initialized; use 'var " + var_name + " = null' if no value is needed")
}
ast_node_end(node)
push(decls, node)
@@ -1037,6 +1092,11 @@ var parse = function(tokens, src, filename, tokenizer) {
else parse_error(tok, "expected ')' after if condition")
then_stmts = []
node.then = then_stmts
saved_ct = _control_type
saved_cd = _control_depth
_control_type = "if"
_control_depth = _control_depth + 1
_expecting_body = true
body = parse_statement()
if (body != null) push(then_stmts, body)
else_ifs = []
@@ -1044,15 +1104,22 @@ var parse = function(tokens, src, filename, tokenizer) {
if (tok.kind == "else") {
advance()
if (tok.kind == "if") {
_control_depth = saved_cd
_control_type = saved_ct
elif = parse_statement()
if (elif != null) push(else_ifs, elif)
ast_node_end(node)
return node
} else {
else_stmts = []
node.else = else_stmts
_expecting_body = true
body = parse_statement()
if (body != null) push(else_stmts, body)
}
}
_control_depth = saved_cd
_control_type = saved_ct
ast_node_end(node)
return node
}
@@ -1068,8 +1135,15 @@ var parse = function(tokens, src, filename, tokenizer) {
else parse_error(tok, "expected ')' after while condition")
stmts = []
node.statements = stmts
saved_ct = _control_type
saved_cd = _control_depth
_control_type = "while"
_control_depth = _control_depth + 1
_expecting_body = true
body = parse_statement()
if (body != null) push(stmts, body)
_control_depth = saved_cd
_control_type = saved_ct
ast_node_end(node)
return node
}
@@ -1079,8 +1153,15 @@ var parse = function(tokens, src, filename, tokenizer) {
advance()
stmts = []
node.statements = stmts
saved_ct = _control_type
saved_cd = _control_depth
_control_type = "do"
_control_depth = _control_depth + 1
_expecting_body = true
body = parse_statement()
if (body != null) push(stmts, body)
_control_depth = saved_cd
_control_type = saved_ct
if (tok.kind == "while") advance()
else parse_error(tok, "expected 'while' after do body")
if (tok.kind == "(") advance()
@@ -1101,6 +1182,7 @@ var parse = function(tokens, src, filename, tokenizer) {
else parse_error(tok, "expected '(' after for")
if (tok.kind != ";") {
if (tok.kind == "var" || tok.kind == "def") {
parse_error(tok, "'" + tok.kind + "' declarations cannot appear in the for initializer; declare variables before the for loop")
init = parse_statement()
node.init = init
} else {
@@ -1124,8 +1206,15 @@ var parse = function(tokens, src, filename, tokenizer) {
else parse_error(tok, "expected ')' after for clauses")
stmts = []
node.statements = stmts
saved_ct = _control_type
saved_cd = _control_depth
_control_type = "for"
_control_depth = _control_depth + 1
_expecting_body = true
body = parse_statement()
if (body != null) push(stmts, body)
_control_depth = saved_cd
_control_type = saved_ct
ast_node_end(node)
return node
}

165
tests/decl_restrictions.ce Normal file
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@@ -0,0 +1,165 @@
// Declaration restriction tests
// Run: ./cell tests/decl_restrictions.ce
var tokenize = use("tokenize")
var parse = use("parse")
var passed = 0
var failed = 0
var error_names = []
var error_reasons = []
var fail_msg = ""
var _i = 0
for (_i = 0; _i < 20; _i++) {
error_names[] = null
error_reasons[] = null
}
var fail = function(msg) {
fail_msg = msg
disrupt
}
var run = function(name, fn) {
fail_msg = ""
fn()
passed = passed + 1
} disruption {
error_names[failed] = name
error_reasons[failed] = fail_msg == "" ? "disruption" : fail_msg
failed = failed + 1
}
var parse_snippet = function(src) {
var result = tokenize(src, "<test>")
var ast = parse(result.tokens, src, "<test>", tokenize)
return ast
}
var has_error = function(ast, substring) {
if (ast.errors == null) return false
var i = 0
while (i < length(ast.errors)) {
if (search(ast.errors[i].message, substring) != null) return true
i = i + 1
}
return false
}
var has_no_errors = function(ast) {
return ast.errors == null || length(ast.errors) == 0
}
// === BARE BLOCK ===
run("bare block rejected", function() {
var ast = parse_snippet("{ var x = 1 }")
if (!has_error(ast, "bare block")) fail("expected 'bare block' error, got: " + text(ast.errors))
})
// === VAR IN IF (braces) ===
run("var in if braces", function() {
var ast = parse_snippet("if (true) { var x = 1 }")
if (!has_error(ast, "not inside 'if'")) fail("expected 'not inside if' error, got: " + text(ast.errors))
})
// === VAR IN IF (no braces) ===
run("var in if no braces", function() {
var ast = parse_snippet("if (true) var x = 1")
if (!has_error(ast, "not inside 'if'")) fail("expected 'not inside if' error, got: " + text(ast.errors))
})
// === VAR IN WHILE ===
run("var in while", function() {
var ast = parse_snippet("while (true) { var x = 1; break }")
if (!has_error(ast, "not inside 'while'")) fail("expected 'not inside while' error, got: " + text(ast.errors))
})
// === VAR IN FOR INIT ===
run("var in for init", function() {
var ast = parse_snippet("for (var i = 0; i < 1; i++) {}")
if (!has_error(ast, "for initializer")) fail("expected 'for initializer' error, got: " + text(ast.errors))
})
// === VAR IN FOR BODY ===
run("var in for body", function() {
var ast = parse_snippet("var i = 0; for (i = 0; i < 1; i++) { var x = 1 }")
if (!has_error(ast, "not inside 'for'")) fail("expected 'not inside for' error, got: " + text(ast.errors))
})
// === VAR IN DO ===
run("var in do", function() {
var ast = parse_snippet("do { var x = 1; break } while (true)")
if (!has_error(ast, "not inside 'do'")) fail("expected 'not inside do' error, got: " + text(ast.errors))
})
// === DEF IN IF ===
run("def in if", function() {
var ast = parse_snippet("if (true) { def x = 1 }")
if (!has_error(ast, "not inside 'if'")) fail("expected 'not inside if' error, got: " + text(ast.errors))
})
// === UNINITIALIZED VAR ===
run("uninitialized var", function() {
var ast = parse_snippet("var x")
if (!has_error(ast, "must be initialized")) fail("expected 'must be initialized' error, got: " + text(ast.errors))
})
// === NESTED: VAR IN IF INSIDE WHILE ===
run("nested var in if inside while", function() {
var ast = parse_snippet("while (true) { if (true) { var x = 1 }; break }")
if (!has_error(ast, "not inside 'if'")) fail("expected 'not inside if' error, got: " + text(ast.errors))
})
// === VALID: NESTED FUNCTION ===
run("valid nested fn in control flow", function() {
var ast = parse_snippet("if (true) { var fn = function() { var x = 1; return x } }")
// The var inside the function is fine; only the var fn = ... inside if should error
if (!has_error(ast, "not inside 'if'")) fail("expected error for var fn inside if")
// But there should NOT be an error about var x inside the function body
var i = 0
var bad = false
if (ast.errors != null) {
while (i < length(ast.errors)) {
if (search(ast.errors[i].message, "var x") != null) bad = true
i = i + 1
}
}
if (bad) fail("should not error on var inside nested function")
})
// === VALID: NORMAL VAR ===
run("valid normal var", function() {
var ast = parse_snippet("var x = 1")
if (!has_no_errors(ast)) fail("expected no errors, got: " + text(ast.errors))
})
// === VALID: VAR IN FUNCTION BODY ===
run("valid var in function body", function() {
var ast = parse_snippet("var fn = function() { var x = 1; return x }")
if (!has_no_errors(ast)) fail("expected no errors, got: " + text(ast.errors))
})
// === SUMMARY ===
print(text(passed) + " passed, " + text(failed) + " failed out of " + text(passed + failed))
var _j = 0
if (failed > 0) {
print("")
for (_j = 0; _j < failed; _j++) {
print(" FAIL " + error_names[_j] + ": " + error_reasons[_j])
}
}