From 2c5117ba22c13cec2910bfe6daea2891a8ac6b1d Mon Sep 17 00:00:00 2001
From: Anna Kozlova <anna.kozlova@jetbrains.com>
Date: Wed, 30 May 2018 20:34:20 +0300
Subject: [PATCH] completion: presume fresh variables have always low bounds
 during completion

IDEA-190041
---
 .../resolve/CompletionParameterTypeInferencePolicy.java  | 5 +++++
 .../source/resolve/ParameterTypeInferencePolicy.java     | 9 +++++++++
 .../smartType/LowerBoundOfFreshVariable-out.java         | 9 +++++++++
 .../completion/smartType/LowerBoundOfFreshVariable.java  | 9 +++++++++
 .../completion/SmartType18CompletionTest.java            | 5 +++++
 5 files changed, 37 insertions(+)
 create mode 100644 java/java-tests/testData/codeInsight/completion/smartType/LowerBoundOfFreshVariable-out.java
 create mode 100644 java/java-tests/testData/codeInsight/completion/smartType/LowerBoundOfFreshVariable.java

diff --git a/java/java-impl/src/com/intellij/psi/impl/source/resolve/CompletionParameterTypeInferencePolicy.java b/java/java-impl/src/com/intellij/psi/impl/source/resolve/CompletionParameterTypeInferencePolicy.java
index 9100174f0f3f..429a949051ed 100644
--- a/java/java-impl/src/com/intellij/psi/impl/source/resolve/CompletionParameterTypeInferencePolicy.java
+++ b/java/java-impl/src/com/intellij/psi/impl/source/resolve/CompletionParameterTypeInferencePolicy.java
@@ -66,4 +66,9 @@ public class CompletionParameterTypeInferencePolicy extends ProcessCandidatePara
   public boolean isVarargsIgnored() {
     return true;
   }
+
+  @Override
+  public boolean inferLowerBoundForFreshVariables() {
+    return true;
+  }
 }
diff --git a/java/java-psi-api/src/com/intellij/psi/impl/source/resolve/ParameterTypeInferencePolicy.java b/java/java-psi-api/src/com/intellij/psi/impl/source/resolve/ParameterTypeInferencePolicy.java
index 9b9cfce7ab72..81a4b4de59db 100644
--- a/java/java-psi-api/src/com/intellij/psi/impl/source/resolve/ParameterTypeInferencePolicy.java
+++ b/java/java-psi-api/src/com/intellij/psi/impl/source/resolve/ParameterTypeInferencePolicy.java
@@ -42,4 +42,13 @@ public abstract class ParameterTypeInferencePolicy {
   public boolean isVarargsIgnored() {
     return false;
   }
+
+  /**
+   * For infinite type declarations, like {@code Foo<T extends Foo<T>>}, inference introduces fake fresh "fixed" type parameters.
+   * These fresh parameters respect constraints, created during inference session. For completion, it makes sense to define lower bounds
+   * even if no appropriate constraints were detected, as probably the corresponding argument is currently completed. 
+   */
+  public boolean inferLowerBoundForFreshVariables() {
+    return false;
+  }
 }
diff --git a/java/java-tests/testData/codeInsight/completion/smartType/LowerBoundOfFreshVariable-out.java b/java/java-tests/testData/codeInsight/completion/smartType/LowerBoundOfFreshVariable-out.java
new file mode 100644
index 000000000000..8449cdd7c422
--- /dev/null
+++ b/java/java-tests/testData/codeInsight/completion/smartType/LowerBoundOfFreshVariable-out.java
@@ -0,0 +1,9 @@
+
+interface Foo<T extends Foo<T>> {
+
+    static <F extends Foo<F>> void foo(F f) {
+        bar(f);<caret>
+    }
+
+    static <B extends Foo<B>> void bar(B b) { }
+}
\ No newline at end of file
diff --git a/java/java-tests/testData/codeInsight/completion/smartType/LowerBoundOfFreshVariable.java b/java/java-tests/testData/codeInsight/completion/smartType/LowerBoundOfFreshVariable.java
new file mode 100644
index 000000000000..0adbc564775c
--- /dev/null
+++ b/java/java-tests/testData/codeInsight/completion/smartType/LowerBoundOfFreshVariable.java
@@ -0,0 +1,9 @@
+
+interface Foo<T extends Foo<T>> {
+
+    static <F extends Foo<F>> void foo(F f) {
+        bar(<caret>);
+    }
+
+    static <B extends Foo<B>> void bar(B b) { }
+}
\ No newline at end of file
diff --git a/java/java-tests/testSrc/com/intellij/java/codeInsight/completion/SmartType18CompletionTest.java b/java/java-tests/testSrc/com/intellij/java/codeInsight/completion/SmartType18CompletionTest.java
index d8c9221ba182..f57975355de0 100644
--- a/java/java-tests/testSrc/com/intellij/java/codeInsight/completion/SmartType18CompletionTest.java
+++ b/java/java-tests/testSrc/com/intellij/java/codeInsight/completion/SmartType18CompletionTest.java
@@ -224,6 +224,11 @@ public void testConvertToObjectStream() {
     myFixture.complete(CompletionType.SMART, 1);
     checkResultByFile("/" + getTestName(false) + "-out.java");
   }
+  public void testLowerBoundOfFreshVariable() { 
+    configureByTestName();
+    myFixture.complete(CompletionType.SMART, 1);
+    checkResultByFile("/" + getTestName(false) + "-out.java");
+  }
 
   private void doTest() {
     doTest(true);