Add tests

source/compiler/tests/warning_250_251.meta

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+{
+  'test_type': 'output_check',
+  'errors': """
+warning_250_251.pwn(12) : warning 250: variable "n" used in loop condition not modified in loop body
+warning_250_251.pwn(13) : warning 250: variable "i" used in loop condition not modified in loop body
+warning_250_251.pwn(31) : warning 250: variable "n" used in loop condition not modified in loop body
+warning_250_251.pwn(32) : warning 250: variable "i" used in loop condition not modified in loop body
+warning_250_251.pwn(46) : warning 251: none of the variables used in loop condition are modified in loop body
+warning_250_251.pwn(47) : warning 251: none of the variables used in loop condition are modified in loop body
+"""
+}

source/compiler/tests/warning_250_251.pwn

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+#include <core>
+#include <file>
+
+new glbvar = 0;
+
+main()
+{
+	new n = 0, m = 10;
+	static st = 0;
+
+	// Case 1: Variable is used inside a loop condition without being modified.
+	while (n < 10) {}                      // warning 250: variable used in loop condition not modified in loop body (symbol "n")
+	for (new i = 0, j = 0; i < 10; ++j) {} // warning 250: variable used in loop condition not modified in loop body (symbol "i")
+
+	// Case 2: Variable is used inside a loop condition and modified in the loop body.
+	while (n != 0) { n++; }
+	for (new i = 0; i < 10; ) { i++; }
+
+	// Case 3: Variable is used inside a loop condition and modified in the
+	// loop counter increment/decrement section.
+	for (new i = 0; i < 10; i++) {}
+
+	// Case 4: Variable is used and modified inside a loop condition.
+	while (n++ != 0) {}
+	while (++n != 0) {}
+	for (new i = 0; i++ < 10; ) {}
+	for (new i = 0; ++i < 10; ) {}
+
+	// Case 5: Same variable is used inside a loop condition more than once
+	// and it's not modified.
+	while (n == 0 || n < 10) {}            // warning 250: variable used in loop condition not modified in loop body (symbol "n")
+	for (new i = 0; i == 0 || i < 10; ) {} // warning 250: variable used in loop condition not modified in loop body (symbol "i")
+
+	// Case 6: Same variable is used inside a loop condition more than once,
+	// but it's modified.
+	while (n == 0 || n < 10) { n++; }
+	for (new i = 0; i == 0 || i < 10; i++) {}
+
+	// Case 7: Two variables are used inside a loop condition, both aren't modified.
+	// Printing warning 250 for each unmodified variable wouldn't be productive, because:
+	//   1. the user would be spammed with multiple warnings, which can be annoying;
+	//   2. depending on the context, only one of the variables might be supposed
+	//      to be modified, but the compiler can't know which one exactly.
+	// Solution: introduce a warning that simply says that none of the variables
+	// were modified, and let the user decide which variable should be modified.
+	while (n < m) {}            // warning 251: none of the variables used in loop condition are modified in loop body
+	for (new i = 0; i < m; ) {} // warning 251: none of the variables used in loop condition are modified in loop body
+
+	// Case 7: Two variables are used in a loop condition, but one of them
+	// is modified inside the loop body (or the loop counter increment/decrement
+	// section of a "for" loop), and the other one is not modified.
+	while (n < m) { ++n; }
+	for (new i = 0; i < m; ) { i++; }
+	for (new i = 0; i < m; i++) {}
+
+	// Case 8: Two variables are used in a loop condition, but one of them
+	// is being modified prior to being used, and the other one is not modified.
+	while (++n < m) {}
+	for (new i = 0; ++i < m; ) {}
+
+	// Case 9: Two variables are used in a loop condition, but one of them
+	// is static and it's modified inside the loop body, and the other one
+	// is a stack variable and it's left unmodified.
+	while (st < m) { st++; }
+
+	// Case 10: Warnings 250 and 251 may be inaccurate when an array is indexed
+	// inside a loop condition. The problem is that we can't memoize the array
+	// that is being indexed by a variable, to unset the "uLOOPVAR" flag for the
+	// array symbol later when the variable is modified.
+	// This is why I had to completely disable those diagnostics for arrays.
+	{
+		new a[3] = { 0, 0, 1 };
+		n = random(sizeof(a));
+		while (a[n] == 0) // Shouldn't warn about "n" not being modified
+			a[n] = random(3);
+		for (new i = 0; a[i++] == 0; ) {} // shouldn't warn about "a" not being modified
+		for (a[0] = 0, m = 10; a[0] < m; ++a[0]) {} // shouldn't warn about "m" not being modified
+	}
+
+	// Case 11: Just as with arrays, warnings 250 and 251 are disabled when
+	// there's a function call inside a loop condition, as those diagnostics
+	// may be inaccurate otherwise.
+	new File:f = fopen("test.txt", io_read);
+	new line[128];
+	while(fread(f,line,sizeof(line),false) < m) {} // shouldn't warn about "f" or "m" not being modified
+	fclose(f);
+
+	// Case 12: Warnings 250 and 251 don't work for global variables (yet?)
+	while (glbvar < 10) {}
+	for (glbvar = 0; glbvar < 10; ) {}
+}
+