[dev.typeparams] cmd/compile: fix small -G=3 issues for tests disabled in run.go

 - set correct position for closure capture variable in (*irgen).use()
   (issue20250.go) Also, evaluate rhs, lhs in that order in assignment
   statements to match noder1 (affects ordering of closure variables).

 - make sure to set Assign flag properly in (*irgen).forStmt() for range
   variables which are map accesses (issue9691.go)

 - make sure CheckSize() is call on the base type for top-level types
   converted by (*irgen).typ() that are pointer types (issue20174.go and
   issue37837.go)

 - deal with parentheses properly in validation function
   (*irgen).validate() (issue17270.go)

 - avoid HasNil call on type TTYPEPARAM - types2 typechecker will have
   already checked validity of the typeparam having nil value (new test
   issue39755.go)

Change-Id: Ie68004d964698aea047e19e7dcd79b297e9d47ca
Reviewed-on: https://go-review.googlesource.com/c/go/+/334733
Trust: Dan Scales <danscales@google.com>
Run-TryBot: Dan Scales <danscales@google.com>
TryBot-Result: Go Bot <gobot@golang.org>
Reviewed-by: Keith Randall <khr@golang.org>

2 files changed, 28 insertions, 6 deletions

diff --git a/test/run.go b/test/run.go
index 82d49270f2..3ccf1046ce 100644
--- a/test/run.go
+++ b/test/run.go
@@ -2167,12 +2167,7 @@ var types2Failures32Bit = setOf(
 )
 
 var g3Failures = setOf(
-	"writebarrier.go",         // correct diagnostics, but different lines (probably irgen's fault)
-	"fixedbugs/issue17270.go", // ICE in irgen
-	"fixedbugs/issue20174.go", // ICE due to width not calculated (probably irgen's fault)
-	"fixedbugs/issue20250.go", // correct diagnostics, but different lines (probably irgen's fault)
-	"fixedbugs/issue37837.go", // ICE due to width not calculated
-	"fixedbugs/issue9691.go",  // "cannot assign to int(.autotmp_4)" (probably irgen's fault)
+	"writebarrier.go", // correct diagnostics, but different lines (probably irgen's fault)
 
 	"typeparam/nested.go", // -G=3 doesn't support function-local types with generics
 
diff --git a/test/typeparam/issue39755.go b/test/typeparam/issue39755.go
new file mode 100644
index 0000000000..13a575d16f
--- /dev/null
+++ b/test/typeparam/issue39755.go
@@ -0,0 +1,27 @@
+// compile -G=3
+
+// Copyright 2020 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// copied from cmd/compile/internal/types2/testdata/fixedbugs/issue39755.go
+
+package p
+
+func _[T interface{~map[string]int}](x T) {
+	_ = x == nil
+}
+
+// simplified test case from issue
+
+type PathParamsConstraint interface {
+        ~map[string]string | ~[]struct{key, value string}
+}
+
+type PathParams[T PathParamsConstraint] struct {
+	t T
+}
+
+func (pp *PathParams[T]) IsNil() bool {
+	return pp.t == nil // this must succeed
+}