analyzer: check borrow returns of forward-called functions at the unit's end; borrows clause for prototypes, definitions, externs and function types, checked against the body

8 files changed, 90 insertions, 0 deletions

diff --git a/tests/errors/borrows_body.zc b/tests/errors/borrows_body.zc
new file mode 100644
index 0000000..e6c92c6
--- /dev/null
+++ b/tests/errors/borrows_body.zc
@@ -0,0 +1,13 @@
+namespace;
+include rt;
+
+// expect: first: returns a borrow of b, but its borrows clause doesn't name it
+// the body is checked against the prototype's borrows clause.
+char* first(char* a, char* b) borrows a;
+fn main() {
+	char* t = rt.new(4); t[0] = 'x'; t[1] = 0;
+	char* u = rt.new(4); u[0] = 'y'; u[1] = 0;
+	let r = first(t, u); rt.put_c(r[0]); rt.free(u); rt.free(t);
+	return 0;
+}
+char* first(char* a, char* b) { return b; }
diff --git a/tests/errors/borrows_decl.zc b/tests/errors/borrows_decl.zc
new file mode 100644
index 0000000..5229979
--- /dev/null
+++ b/tests/errors/borrows_decl.zc
@@ -0,0 +1,14 @@
+namespace;
+include rt;
+
+// expect: r: used after it was given away; r borrows t, and t was freed on line 11 (t declared on line 8)
+// a prototype's borrows clause ties the result to the first argument's owner only.
+char* first(char* a, char* b) borrows a;
+fn main() {
+	char* t = rt.new(4); t[0] = 'x'; t[1] = 0;
+	char* u = rt.new(4); u[0] = 'y'; u[1] = 0;
+	let r = first(t, u); rt.free(u); rt.put_c(r[0]);
+	rt.free(t); rt.put_c(r[0]);
+	return 0;
+}
+char* first(char* a, char* b) { return a; }
diff --git a/tests/errors/borrows_extern.zc b/tests/errors/borrows_extern.zc
new file mode 100644
index 0000000..e9285d4
--- /dev/null
+++ b/tests/errors/borrows_extern.zc
@@ -0,0 +1,11 @@
+namespace;
+include rt;
+
+// expect: r: used after it was given away; r borrows t, and t was freed on line 9 (t declared on line 8)
+// an extern declares its borrow return by parameter position.
+extern char* strchr(char*, int) borrows 0;
+fn main() {
+	char* t = rt.new(4); t[0] = 'x'; t[1] = 0;
+	let r = strchr(t, 'x'); rt.free(t); rt.put_c(r[0]);
+	return 0;
+}
diff --git a/tests/errors/borrows_fntype.zc b/tests/errors/borrows_fntype.zc
new file mode 100644
index 0000000..a73b0d8
--- /dev/null
+++ b/tests/errors/borrows_fntype.zc
@@ -0,0 +1,12 @@
+namespace;
+include rt;
+
+// expect: r: used after it was given away; r borrows t, and t was freed on line 10 (t declared on line 9)
+// a function type carries a borrows clause, by parameter position.
+char* skip(char* s) { return s + 1; }
+fn main() {
+	char*(char*) borrows 0 f = skip;
+	char* t = rt.new(4); t[0] = 'x'; t[1] = 'y'; t[2] = 0;
+	let r = f(t); rt.free(t); rt.put_c(r[0]);
+	return 0;
+}
diff --git a/tests/errors/forward_borrow_return.zc b/tests/errors/forward_borrow_return.zc
new file mode 100644
index 0000000..6c3ae93
--- /dev/null
+++ b/tests/errors/forward_borrow_return.zc
@@ -0,0 +1,11 @@
+namespace;
+include rt;
+
+// expect: r: used after it was given away; r borrows t, and t was freed on line 8 (t declared on line 7); skip, defined after this call, returns a borrow of its argument
+// skip is called before its body: its borrow return is checked when the body is read.
+fn main() {
+	char* t = rt.new(8); t[0] = ' '; t[1] = 'a'; t[2] = 0;
+	let r = skip(t); rt.free(t); rt.put_c(r[0]);
+	return 0;
+}
+char* skip(char* s) { int i = 0; while (s[i] == ' ') i++; return s + i; }
diff --git a/tests/programs/borrows_clause.zc b/tests/programs/borrows_clause.zc
new file mode 100644
index 0000000..6f43581
--- /dev/null
+++ b/tests/programs/borrows_clause.zc
@@ -0,0 +1,11 @@
+namespace;
+include rt;
+// a borrows clause on a prototype and its definition: freeing the other argument keeps the result.
+char* first(char* a, char* b) borrows a;
+fn main() {
+	char* t = rt.new(4); t[0] = 'x'; t[1] = 0;
+	char* u = rt.new(4); u[0] = 'y'; u[1] = 0;
+	let r = first(t, u); rt.free(u); rt.put_c(r[0]); rt.free(t);
+	return 0;
+}
+char* first(char* a, char* b) borrows a { return a; }
diff --git a/tests/programs/forward_borrow.zc b/tests/programs/forward_borrow.zc
new file mode 100644
index 0000000..7cc44b1
--- /dev/null
+++ b/tests/programs/forward_borrow.zc
@@ -0,0 +1,16 @@
+namespace;
+include rt;
+// forward calls whose results do not outlive the owner, or do not borrow it, are accepted.
+fn main() {
+	char* t = rt.new(8); t[0] = ' '; t[1] = 'a'; t[2] = 0;
+	let n = count(t); rt.free(t); rt.put_n(n);
+	let u = rt.new(8); u[0] = 'b'; u[1] = 0;
+	let r = skip(u); rt.put_c(r[0]); rt.free(u);
+	let v = rt.new(8); v[0] = 0;
+	let q = skip(v); rt.free(v); q = 0; rt.put_n(q);
+	let w = rt.new(8); w[0] = 0;
+	let k = skip(w)[0]; rt.free(w); rt.put_n(k);
+	return 0;
+}
+int count(char* s) { int i = 0; while (s[i]) i++; return i; }
+char* skip(char* s) { int i = 0; while (s[i] == ' ') i++; return s + i; }
diff --git a/tests/test.sh b/tests/test.sh
index 7745a66..d8ad0fb 100755
--- a/tests/test.sh
+++ b/tests/test.sh
@@ -216,6 +216,8 @@ ABC" "$l o3 lifts byte loads and stores"
 	chk "$($vm < tests/programs/o3.zc)" "3142 42 43 9 57 98781 520625 10192 -18782 1152" "$l o3 regions: loops, calls, recursion, switch, arrays, more vars than registers"
 	chk "$($vm < tests/programs/o3scopes.zc)" "116" "$l o3 registers shared by scopes, cached fixed arrays"
 	chk "$($vm < tests/programs/borrow_rules.zc)" "$(cat tests/programs/borrow_rules.expected)" "$l inferred transfers, projections and shared closure cells"
+	chk "$($vm < tests/programs/forward_borrow.zc)" "2b00" "$l forward calls: results that do not borrow, or are not used after the owner ends, are accepted"
+	chk "$($vm < tests/programs/borrows_clause.zc)" "x" "$l a borrows clause ties the result to the named argument only"
 	chk "$($vm < tests/programs/replace_owner.zc)" "$(cat tests/programs/replace_owner.expected)" "$l replacing a released owner moves ownership and cleans up once"
 	chk "$($vm < tests/programs/temporary_borrows.zc)" "$(cat tests/programs/temporary_borrows.expected)" "$l temporary borrows preserve aliases and release allocations"
 	chk "$($vm < tests/programs/array_values.zc)" "$(cat tests/programs/array_values.expected)" "$l array initializers, designators, zero filling, nested and compound literals"