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fix(library/definitional/equations): add more equation validation to avoid obscure error message

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Leonardo de Moura 2015-01-09 18:52:21 -08:00
parent 2e4a2451e6
commit a3bc1b0cd5
3 changed files with 23 additions and 5 deletions
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19
src/library/definitional/equations.cpp
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@ -315,6 +315,7 @@ class equation_compiler_fn {
[[ noreturn ]] static void throw_error(char const * msg, expr const & src) { throw_generic_exception(msg, src); }
[[ noreturn ]] static void throw_error(expr const & src, pp_fn const & fn) { throw_generic_exception(src, fn); }
[[ noreturn ]] void throw_error(sstream const & ss) const { throw_generic_exception(ss, m_meta); }
[[ noreturn ]] void throw_error(expr const & src, sstream const & ss) const { throw_generic_exception(ss, src); }
void check_limitations(expr const & eqns) const {
if (is_wf_equations(eqns) && equations_num_fns(eqns) != 1)
@ -478,19 +479,27 @@ class equation_compiler_fn {
validate_exception(expr const & e):m_expr(e) {}
};
void check_in_local_ctx(expr const & e, buffer<expr> const & local_ctx) {
if (!contains_local(e, local_ctx))
throw_error(e, sstream() << "invalid recursive equation, variable '" << e
<< "' has the same name of a variable in an outer-scope (solution: rename this variable)");
}
// Validate/normalize the given pattern.
// It stores in reachable_vars any variable that does not occur
// in inaccessible terms.
expr validate_pattern(expr pat, name_set & reachable_vars) {
expr validate_pattern(expr pat, buffer<expr> const & local_ctx, name_set & reachable_vars) {
if (is_inaccessible(pat))
return pat;
if (is_local(pat)) {
reachable_vars.insert(mlocal_name(pat));
check_in_local_ctx(pat, local_ctx);
return pat;
}
expr new_pat = whnf(pat);
if (is_local(new_pat)) {
reachable_vars.insert(mlocal_name(new_pat));
check_in_local_ctx(new_pat, local_ctx);
return new_pat;
}
buffer<expr> pat_args;
@ -498,7 +507,7 @@ class equation_compiler_fn {
if (auto in = is_constructor(fn)) {
unsigned num_params = *inductive::get_num_params(env(), *in);
for (unsigned i = num_params; i < pat_args.size(); i++)
pat_args[i] = validate_pattern(pat_args[i], reachable_vars);
pat_args[i] = validate_pattern(pat_args[i], local_ctx, reachable_vars);
return mk_app(fn, pat_args, pat.get_tag());
} else {
throw validate_exception(pat);
@ -509,10 +518,10 @@ class equation_compiler_fn {
// The lhs is only used to report errors.
// It stores in reachable_vars any variable that does not occur
// in inaccessible terms.
void validate_patterns(expr const & lhs, buffer<expr> & patterns, name_set & reachable_vars) {
void validate_patterns(expr const & lhs, buffer<expr> const & local_ctx, buffer<expr> & patterns, name_set & reachable_vars) {
for (expr & pat : patterns) {
try {
pat = validate_pattern(pat, reachable_vars);
pat = validate_pattern(pat, local_ctx, reachable_vars);
} catch (validate_exception & ex) {
expr problem_expr = ex.m_expr;
throw_error(lhs, [=](formatter const & fmt) {
@ -546,7 +555,7 @@ class equation_compiler_fn {
buffer<expr> patterns;
expr const & fn = get_app_args(lhs, patterns);
name_set reachable_vars;
validate_patterns(lhs, patterns, reachable_vars);
validate_patterns(lhs, local_ctx, patterns, reachable_vars);
for (expr const & v : local_ctx) {
// every variable in the local_ctx must be "reachable".
if (!reachable_vars.contains(mlocal_name(v))) {

8
tests/lean/shadow.lean Normal file
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@ -0,0 +1,8 @@
open nat
variable a : nat
-- The variable 'a' in the following definition is not the variable 'a' above
definition tadd : nat → nat → nat,
tadd zero b := b,
tadd (succ a) b := succ (tadd a b)

1
tests/lean/shadow.lean.expected.out Normal file
View file

@ -0,0 +1 @@
shadow.lean:8:11: error: invalid recursive equation, variable 'a' has the same name of a variable in an outer-scope (solution: rename this variable)