• griesemer's avatar
    spec: clarify context type for certain non-constant shifts · 9690d245
    griesemer authored
    The spec is not conclusive about whether a non-constant shift of
    certain untyped constant left operands is valid when the shift
    expression appears as an index in an index or slice expression,
    or as a size in a `make` function call.
    
    Despite identical spec rules in all these cases, cmd/compile accepts
    
    	make([]byte, 1.0 << s)
    
    but pronounces an error for
    
    	a[1.0 << s]
    
    (go/types accepts both).
    
    This change clarifies the spec by explicitly stating that an
    untyped constant left operand in a non-constant shift (1.0 in
    the above examples) will be given type `int` in these contexts.
    
    A separate issue #21693 addresses the cmd/compile bug.
    
    Fixes #14844.
    
    Change-Id: I4b52125e487a607fae377fcbed55463cdce9836c
    Reviewed-on: https://go-review.googlesource.com/60230Reviewed-by: 's avatarRuss Cox <rsc@golang.org>
    Reviewed-by: 's avatarIan Lance Taylor <iant@golang.org>
    9690d245
go_spec.html 200 KB