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Improve XorPower #4465

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Jul 15, 2024
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Improve XorPower #4465

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34 changes: 26 additions & 8 deletions core/src/main/java/com/google/errorprone/bugpatterns/XorPower.java
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Original file line number Diff line number Diff line change
Expand Up @@ -18,8 +18,8 @@

import static com.google.errorprone.BugPattern.SeverityLevel.ERROR;
import static com.google.errorprone.matchers.Description.NO_MATCH;
import static com.google.errorprone.util.ASTHelpers.getStartPosition;

import com.google.common.base.Strings;
import com.google.errorprone.BugPattern;
import com.google.errorprone.VisitorState;
import com.google.errorprone.bugpatterns.BugChecker.BinaryTreeMatcher;
Expand All @@ -37,21 +37,31 @@ public Description matchBinary(BinaryTree tree, VisitorState state) {
if (!tree.getKind().equals(Tree.Kind.XOR)) {
return NO_MATCH;
}
Integer lhs = ASTHelpers.constValue(tree.getLeftOperand(), Integer.class);
Tree lhsTree = tree.getLeftOperand();
while (lhsTree instanceof BinaryTree) {
lhsTree = ((BinaryTree) lhsTree).getRightOperand();
}
Number lhs = ASTHelpers.constValue(lhsTree, Number.class);
if (lhs == null) {
return NO_MATCH;
}
if (lhs.longValue() != lhs.intValue()) {
return NO_MATCH;
}
switch (lhs.intValue()) {
case 2:
case 10:
break;
default:
return NO_MATCH;
}
Integer rhs = ASTHelpers.constValue(tree.getRightOperand(), Integer.class);
Number rhs = ASTHelpers.constValue(tree.getRightOperand(), Number.class);
if (rhs == null) {
return NO_MATCH;
}
if (rhs.longValue() != rhs.intValue()) {
return NO_MATCH;
}
if (state.getSourceForNode(tree.getRightOperand()).startsWith("0")) {
// hex and octal literals
return NO_MATCH;
Expand All @@ -62,16 +72,24 @@ public Description matchBinary(BinaryTree tree, VisitorState state) {
String.format(
"The ^ operator is binary XOR, not a power operator, so '%s' will always"
+ " evaluate to %d.",
state.getSourceForNode(tree), lhs ^ rhs));
state.getSourceForNode(tree), lhs.intValue() ^ rhs.intValue()));
String suffix = lhs instanceof Long ? "L" : "";
int start = getStartPosition(lhsTree);
int end = state.getEndPosition(tree);
switch (lhs.intValue()) {
case 2:
if (rhs <= 31) {
description.addFix(SuggestedFix.replace(tree, String.format("1 << %d", rhs)));
if (rhs.intValue() <= (lhs instanceof Long ? 63 : 31)) {
String replacement = String.format("1%s << %d", suffix, rhs);
if (start != getStartPosition(tree)) {
replacement = "(" + replacement + ")";
}
description.addFix(SuggestedFix.replace(start, end, replacement));
}
break;
case 10:
if (rhs <= 9) {
description.addFix(SuggestedFix.replace(tree, "1" + Strings.repeat("0", rhs)));
if (rhs.intValue() <= (lhs instanceof Long ? 18 : 9)) {
description.addFix(
SuggestedFix.replace(start, end, "1" + "0".repeat(rhs.intValue()) + suffix));
}
break;
default:
Expand Down
50 changes: 48 additions & 2 deletions core/src/test/java/com/google/errorprone/bugpatterns/XorPowerTest.java
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Original file line number Diff line number Diff line change
Expand Up @@ -32,15 +32,15 @@ public void positive() {
"Test.java",
"class Test {",
" static final int X = 2 ^ 16;",
" static final int Y = 2 ^ 32;",
" static final int TOO_BIG = 2 ^ 32;",
" static final int Z = 2 ^ 31;",
" static final int P = 10 ^ 6;",
"}")
.addOutputLines(
"Test.java",
"class Test {",
" static final int X = 1 << 16;",
" static final int Y = 2 ^ 32;",
" static final int TOO_BIG = 2 ^ 32;",
" static final int Z = 1 << 31;",
" static final int P = 1000000;",
"}")
Expand All @@ -59,4 +59,50 @@ public void negative() {
"}")
.doTest();
}

@Test
public void positiveLongs() {
BugCheckerRefactoringTestHelper.newInstance(XorPower.class, getClass())
.addInputLines(
"Test.java",
"class Test {",
" static final long X = 2L ^ 16;",
" static final long Y = 2L ^ 32;",
" static final long Z = 2L ^ 31;",
" static final long TOO_BIG = 2L ^ 64;",
" static final long P = 10L ^ 6;",
"}")
.addOutputLines(
"Test.java",
"class Test {",
" static final long X = 1L << 16;",
" static final long Y = 1L << 32;",
" static final long Z = 1L << 31;",
" static final long TOO_BIG = 2L ^ 64;",
" static final long P = 1000000L;",
"}")
.doTest();
}

@Test
public void precedence() {
BugCheckerRefactoringTestHelper.newInstance(XorPower.class, getClass())
.addInputLines(
"Test.java", //
"class Test {",
" void f(int i) {",
" int x = i * 2 ^ 16;",
" int y = i * 10 ^ 3;",
" }",
"}")
.addOutputLines(
"Test.java", //
"class Test {",
" void f(int i) {",
" int x = i * (1 << 16);",
" int y = i * 1000;",
" }",
"}")
.doTest();
}
}
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