go/types, types2: better error message for some invalid integer array lengths

Don't say "array length must be integer" if it is in fact an integer.

Fixes #59209

Change-Id: If60b93a0418f5837ac334412d3838eec25eeb855
Reviewed-on: https://go-review.googlesource.com/c/go/+/479115
Reviewed-by: Robert Griesemer <gri@google.com>
Run-TryBot: Robert Griesemer <gri@google.com>
Reviewed-by: Robert Findley <rfindley@google.com>
Auto-Submit: Robert Griesemer <gri@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org>

src/cmd/compile/internal/types2/typexpr.go

@@ -503,13 +503,17 @@ func (check *Checker) arrayLength(e syntax.Expr) int64 {
 				if n, ok := constant.Int64Val(val); ok && n >= 0 {
 					return n
 				}
-				check.errorf(&x, InvalidArrayLen, "invalid array length %s", &x)
-				return -1
 			}
 		}
 	}
 
-	check.errorf(&x, InvalidArrayLen, "array length %s must be integer", &x)
+	var msg string
+	if isInteger(x.typ) {
+		msg = "invalid array length %s"
+	} else {
+		msg = "array length %s must be integer"
+	}
+	check.errorf(&x, InvalidArrayLen, msg, &x)
 	return -1
 }
 

src/go/types/typexpr.go

@@ -494,13 +494,17 @@ func (check *Checker) arrayLength(e ast.Expr) int64 {
 				if n, ok := constant.Int64Val(val); ok && n >= 0 {
 					return n
 				}
-				check.errorf(&x, InvalidArrayLen, "invalid array length %s", &x)
-				return -1
 			}
 		}
 	}
 
-	check.errorf(&x, InvalidArrayLen, "array length %s must be integer", &x)
+	var msg string
+	if isInteger(x.typ) {
+		msg = "invalid array length %s"
+	} else {
+		msg = "array length %s must be integer"
+	}
+	check.errorf(&x, InvalidArrayLen, msg, &x)
 	return -1
 }
 

src/internal/types/testdata/check/decls0.go

@@ -55,7 +55,7 @@ type (
 	// The error message below could be better. At the moment
 	// we believe an integer that is too large is not an integer.
 	// But at least we get an error.
-	iA1 [1 /* ERROR "must be integer" */ <<100]int
+	iA1 [1 /* ERROR "invalid array length" */ <<100]int
 	iA2 [- /* ERROR "invalid array length" */ 1]complex128
 	iA3 ["foo" /* ERROR "must be integer" */ ]string
 	iA4 [float64 /* ERROR "must be integer" */ (0)]int

src/internal/types/testdata/fixedbugs/issue59209.go

@@ -0,0 +1,11 @@
+// Copyright 2023 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.
+
+package p
+
+type (
+	_ [1 /* ERROR "invalid array length" */ << 100]int
+	_ [1.0]int
+	_ [1.1 /* ERROR "must be integer" */ ]int
+)

test/fixedbugs/bug255.go

@@ -13,7 +13,7 @@ var d ["abc"]int // ERROR "invalid array bound|not numeric|must be integer"
 var e [nil]int   // ERROR "use of untyped nil|invalid array (bound|length)|not numeric|must be constant"
 // var f [e]int  // ok with Go 1.17 because an error was reported for e; leads to an error for Go 1.18
 var f [ee]int      // ERROR "undefined|undeclared"
-var g [1 << 65]int // ERROR "array bound is too large|overflows|must be integer"
+var g [1 << 65]int // ERROR "array bound is too large|overflows|invalid array length"
 var h [len(a)]int  // ok
 
 func ff() string

test/fixedbugs/issue49814.go

@@ -7,8 +7,8 @@
 package main
 
 // "must be integer" error is for 32-bit architectures
-type V [1 << 50]byte // ERROR "larger than address space|must be integer"
+type V [1 << 50]byte // ERROR "larger than address space|invalid array length"
 
-var X [1 << 50]byte // ERROR "larger than address space|must be integer"
+var X [1 << 50]byte // ERROR "larger than address space|invalid array length"
 
 func main() {}

test/fixedbugs/issue5609.go

@@ -10,4 +10,4 @@ package pkg
 
 const Large uint64 = 18446744073709551615
 
-var foo [Large]uint64 // ERROR "array bound is too large|array bound overflows|array length.*must be integer"
+var foo [Large]uint64 // ERROR "array bound is too large|array bound overflows|invalid array length"