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cgen: enable string index error handling s[i] or {...} (#10670)

This commit is contained in:
Uwe Krüger 2021-07-05 20:00:30 +02:00 committed by GitHub
parent 9e61321d4c
commit a1f123bd42
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GPG Key ID: 4AEE18F83AFDEB23
3 changed files with 85 additions and 5 deletions

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@ -1263,6 +1263,17 @@ fn (s string) at(idx int) byte {
}
}
// version of `at()` that is used in `a[i] or {`
// return an error when the index is out of range
fn (s string) at_with_check(idx int) ?byte {
if idx < 0 || idx >= s.len {
return error('string index out of range')
}
unsafe {
return s.str[idx]
}
}
// is_space returns `true` if the byte is a white space character.
// The following list is considered white space characters: ` `, `\t`, `\n`, `\v`, `\f`, `\r`, 0x85, 0xa0
// Example: assert byte(` `).is_space() == true

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@ -25,11 +25,28 @@ fn (mut g Gen) index_expr(node ast.IndexExpr) {
g.expr(node.index)
g.write(']')
} else {
g.write('string_at(')
g.expr(node.left)
g.write(', ')
g.expr(node.index)
g.write(')')
gen_or := node.or_expr.kind != .absent || node.is_option
if gen_or {
tmp_opt := g.new_tmp_var()
cur_line := g.go_before_stmt(0)
g.out.write_string(util.tabs(g.indent))
opt_elem_type := g.typ(ast.byte_type.set_flag(.optional))
g.write('$opt_elem_type $tmp_opt = string_at_with_check(')
g.expr(node.left)
g.write(', ')
g.expr(node.index)
g.writeln(');')
if !node.is_option {
g.or_block(tmp_opt, node.or_expr, ast.byte_type)
}
g.write('\n$cur_line*(byte*)&${tmp_opt}.data')
} else {
g.write('string_at(')
g.expr(node.left)
g.write(', ')
g.expr(node.index)
g.write(')')
}
}
} else {
g.expr(node.left)

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@ -0,0 +1,52 @@
fn test_empty_string_access() {
mut res := ''
a := ''
if a[0] or { `0` } == `1` {
res = 'good'
} else {
res = 'bad'
}
assert res == 'bad'
}
fn test_good_string_access() {
mut res := ''
a := 'abcd'
if a[2] or { `0` } == `c` {
res = 'good'
} else {
res = 'bad'
}
assert res == 'good'
}
fn test_if_guard_bad() {
mut res := 'bad'
a := 'xy'
if z := a[2] {
res = '${z:c}'
}
assert res == 'bad'
}
fn test_if_guard_good() {
mut res := 'bad'
a := 'xy123'
if z := a[2] {
res = '${z:c}'
}
assert res == '1'
}
fn get_propagate(s string, i int) ?string {
c := s[i] ?
return 'got `${c:c}`'
}
fn test_propagation() {
s := 'abcd'
x := get_propagate(s, 2) or { '$err' }
y := get_propagate(s, 5) or { '$err' }
assert x == 'got `c`'
assert y == 'string index out of range'
}